The Sun Will Eventually Engulf Earth--Maybe - Scientific American Space The Sun Will Eventually Engulf Earth--Maybe Researchers debate whether Earth will be swallowed by the sun as it expands into a red giant billions of years from now By David Appell on September 1, 2008 Credit: Lynette Cook Photo Researchers, Inc. Advertisement | Report Ad The future looks bright—maybe too bright. The sun is slowly expanding and brightening, and over the next few billion years it will eventually desiccate Earth, leaving it hot, brown and uninhabitable. About 7.6 billion years from now, the sun will reach its maximum size as a red giant: its surface will extend beyond Earth’s orbit today by 20 percent and will shine 3,000 times brighter. In its final stage, the sun will collapse into a white dwarf. Although scientists agree on the sun’s future, they disagree about what will happen to Earth. Since 1924, when British mathematician James Jeans first considered Earth’s fate during the sun’s red giant phase, a bevy of scientists have reached oscillating conclusions. In some scenarios, our planet escapes vaporization; in the latest analyses, however, it does not. The answer is not straightforward, because although the sun will expand beyond Earth’s orbit, or one astronomical unit (AU), it will lose mass along the way. As a result, Earth should drift outward as the gravitational tug lessens over time. (At its maximum radius of 1.2 AU, the sun will have lost about one third of its mass, compared with its current heft.) In this way, Earth could escape solar envelopment. But other factors complicate the analysis. Drag on the planet from the sun’s outermost, tenuous layers will cause Earth to drift inward. Smaller forces from the other planets—all in turn reacting to the same reducing, expanding sun—are even more difficult to account for completely. Earlier this year two teams reported different kinds of calculations indicating that Earth will be swallowed up by the sun. In a calculation that would thrill any college junior studying classical mechanics, Lorenzo Iorio of Italy’s National Institute of Nuclear Physics used perturbation theory. It simplifies analyses by dropping relatively small factors, thereby making complex equations of motions that describe the interactions between the sun and Earth mathematically manageable. Assuming that the sun’s yearly mass loss (currently about one part in 100 trillion) remains small for the duration of its evolution to the red giant phase, Iorio calculates that Earth will move outward at about three millimeters a year, or only 0.0002 AU by the sun’s red giant phase. But at that point the sun will balloon up, in only a million years, to 1.2 AU in radius, thus vaporizing Earth. Iorio’s paper, submitted to Astrophysics and Space Science, has not yet been peer-reviewed. Several scientists question whether quantities that Iorio assumes are small will indeed remain small throughout the sun’s evolution. Even if Iorio got his number crunching wrong, he may have the right answer. In an analysis published in the May Monthly Notices of the Royal Astronomical Society, Klaus-Peter Schröder of the University of Guanajuato in Mexico and Robert Smith of the University of Sussex in England also conclude that Earth is doomed, by using more exact solar models and by considering tidal interactions. As the sun loses mass and expands, its rotation rate must also slow down—physics students learn this relation as the conservation of angular momentum. The slowed rotation causes a tidal bulge on the sun’s surface. The gravity exerted by this bulge pulls Earth inward. With such a consideration, the researchers find that any planet with a present-day orbital radius of less than 1.15 AU will ultimately perish. Could Earth be saved if someone is still left at home? In a bold piece of astronomical engineering, Don Korycansky of the University of California, Santa Cruz, and his colleagues have proposed nudging Earth with a large asteroid arranged to pass nearby periodically. It could take one billion years to move our planet out to somewhe


Which planet takes almost 30 Earth years to orbit the sun?

How Long Is A Year On The Other Planets? - Universe Today   Universe Today How Long Is A Year On The Other Planets? Article Updated: 29 Jan , 2016 by Matt Williams Here on Earth, we to end to not give our measurements of time much thought. Unless we’re griping about Time Zones, enjoying the extra day of a Leap Year, or contemplating the rationality of Daylight Savings Time, we tend to take it all for granted. But when you consider the fact that increments like a year are entirely relative, dependent on a specific space and place, you begin to see how time really works. Here on Earth, we consider a year to be 365 days. Unless of course it’s a Leap Year, which takes place every four years (in which it is 366). But the actual definition of a year is the time it takes our planet to complete a single orbit around the Sun. So if you were to put yourself in another frame of reference – say, another planet – a year would work out to something else. Let’s see just how long a year is on the other planets, shall we? A Year On Mercury: To put it simply, Mercury has an orbital period of 88 days (87.969 to be exact), which means a single year is 88 Earth days – or the equivalent of about 0.241 Earth years. But here’s the thing. Because of Mercury’s slow rotation (once every 58.646 days) and its rapid orbital speed (47.362 km/s), one day on Mercury actually works out to 175.96 Earth days. MESSENGER maps of Mercury – a monochrome map at 250 m/pixel and an eight-color (left), 1-km/pixel color map. Small gaps will be filled in during the next solar day (right). Credit: NASA/Johns Hopkins University APL/Carnegie Institution of Washington So basically, a single year on Mercury is half as long as a Mercurian (aka. Hermian) day. This is due to Mercury being the closest planet to the Sun, ranging from 46,001,200 km at perihelion to 69,816,900 km at aphelion. At that distance, the planet shoots around the Sun faster than any other in our Solar System and has the shortest year. In the course of a year, Mercury experiences intense variations in surface temperature – ranging from 80 °K (-193.15 °C;-315.67 °F) to 700 °K (426.85 °C; 800.33 °F). However, this is due to the planet’s varying distance from the Sun and its spin, which subjects one side to extended periods of extremely hot temperatures and one side to extended periods of night. Mercury’s low axial tilt (0.034°) and its rapid orbital period means that there really is no seasonal variation on Mercury. Basically, one part of the year is as hellishly hot, or horribly cold, as any other. A Year On Venus: The second closest planet to our Sun, Venus completes a single orbit once ever 224.7 days. This means that a single year on Venus works out to about 0.6152 Earth years. But, once again, things are complicated by the fact that Venus has an unusual rotation period. In fact, Venus takes 243 Earth days to rotate once on its axis – the slowest rotation of any planet – and its rotation is retrograde to its orbital path. The planet Venus, as imagined by the Magellan 10 mission. Credit: NASA/JPL Combined with its orbital period, this means that a single solar day on Venus (the time between one sunup to the next) is 117 Earth days. So basically, a single year on Venus is lasts 1.92 Venusian (aka. Cytherean) days. Again, this would make for some confusing time-cycles for any humans trying to make a go of it on Venus! Also, Venus has a very small axial tilt – 3° compared to Earth’s 23.5° – and its proximity to the Sun makes for a much shorter seasonal cycle – 55-58 days compared to Earth’s 90-93 days. Add to that its unusual day-night cycle, variations are very slight. In fact, the temperate on Venus is almost always a brutal 736 K (463 °C ; 865 degrees °F), which is hot enough to melt lead! A Year On Earth: Comparatively speaking, a year on Earth is pretty predictable, which is probably one of the reasons why life is able to thrive here. In short, our planet takes 365.2564 solar days to complete a single orbit of the Sun, which is why we add an extra day to the calendar every four years (i.e. a Leap Yea


What is the most distant object visible to the naked eye?

Farthest Naked Eye Object Farthest Naked Eye Object Loose Ends Maintained by suitti@uitti.net , Stephen Uitti One mostly hears that the Andromeda Galaxy (M31), at 2.25 million (2,250,000) light years is the most distant naked eye object. I've seen it, and it is the farthest naked eye object I've seen. Oh, alright, I was wearing contacts. But without them, or glasses, the most distant object I can see is the Sun. For that, I have to wait until morning. M31 is the largest galaxy in the local group. The Triangulum Spiral (M33) is the third largest member of the Local Group, and some people claim to have seen it with the naked eye. It is a face on spiral galaxy. M33 is more like 2.78 million (2,780,000) light years. Bode's Galaxy (M81), at 12 million (12,000,000) light years has been spotted by several people. This page at SEDS on M81 has a description of how to see it. The trouble is, at Magnitude 6.9, M81 is dimmer than most consider naked eye. It depends on whose eye it is, and also where the feet are standing. It has to be an exceptionally dark sky site, probably at some altitude, at the right time of year, etc. Still, it's my answer to the question. I'm done. Finished. Except for the following speculation. Apparently, SN1987A was a naked eye event. This was the big super nova in the Large Magellanic Cloud (LMC), visible from the southern hemisphere in early 1987. It wasn't a distance record holder, as the LMC is considered a satellite galaxy of the Milky Way. The LMC is only about 100,000 light years out. This is about the distance to the outer edge of the far side of the Milky Way. So one could consider the LMC to be part of the Milky Way. The LMC is already in the process of being torn apart, eaten really, by the Milky Way. The Milky Way is the second largest galaxy in the Local Group. Since super novas can outshine their host galaxies, it seems possible that one could push the farthest object out a bit, if only for a few days. Say there is a galaxy, oh, about 15 million (15,000,000) light years away. It isn't a naked eye object now. But what if it hosts a bright super nova? That object would be the same distance, and could be naked eye visible for a few days. There are other bright things too. I'm not aware of any naked eye visible quasars, for example. There is at least one quasar, 3C 273, visible in a 6 inch (150 mm) telescope. It's magnitude is 12.9. It sits about 2 billion (2,000,000,000) light years away. While no one would call this naked eye observing, it does come under the concept of eyeball astronomy - which is distinguished from astrophotography. How far could one see with eyeball astronomy? That, of course, depends on the telescope. It mostly depends on the light collecting area of the big end of the telescope. There is a story that several people have looked through one of the 10 meter (32.8 foot) Keck telescopes. Each of the twin Keck scopes were, at the time, the largest instruments on Earth. This pushes the concept of eyeball astronomy to interesting limits. Extrapolating from smaller scopes at good dark sky sites, one should be able to see objects as faint as 23rd magnitude with a Keck. Quasars that would appear around that magnitude might be far enough away to be red shifted out of the visible spectrum. But, perhaps higher frequency photons, maybe X-rays, will have been red shifted into the visible spectrum. It seems reasonable to assume that one would be able to peer most of the way back to the beginning of the Universe, or most of the way across the visible part of the Universe. At these distances, due to the expansion of the Universe, light years are not even approximately years back in time. The Universe is about 13.7 billion (13,700,000,000) years old. However, the distance to the most distant detectable objects is about 46 billion (46,000,000,000) light-years.


How Dense Are The Planets? - Universe Today   Universe Today How Dense Are The Planets? Article Updated: 18 Feb , 2016 by Matt Williams The eight planets of our Solar System vary widely, not only in terms of size, but also in terms of mass and density (i.e. its mass per unit of volume). For instance, the 4 inner planets – those that are closest to the Sun – are all terrestrial planets , meaning they are composed primarily of silicate rocks or metals and have a solid surface. On these planets, density varies the farther one ventures from the surface towards the core, but not considerably. By contrast, the 4 outer planets are designated as gas giants (and/or ice giants) which are composed primarily of of hydrogen, helium, and water existing in various physical states. While these planets are greater in size and mass, their overall density is much lower. In addition, their density varies considerably between the outer and inner layers, ranging from a liquid state to materials so dense that they become rock-solid. Density also plays a vital role in determining a planet’s surface gravity and is intrinsic to understanding how a planet formed. After the formation of the Sun at the center of our Solar System, the planets were formed from a protoplanetary disc . Whereas the terrestrial planets resulted from dust grains in the inner Solar System, planets in the outer Solar System accreted enough matter for their gravity to hold on to the nebula’s leftover gas. The Solar System. Image Credit: NASA The more gas they held onto, the larger they became. And the larger they became, the more matter they would accumulate, until such tie that they reached a critical point. Whereas the gas giants of Jupiter and Saturn grew exponentially, the ice giants (Uranus and Neptune), with only a few Earth masses of nebular gas, never reached that critical point. In all cases, density is measured as the number of grams per cubic cm (or g/cm³). Density of Mercury: Ad a terrestrial planet, Mercury is composed of metals and silicate material. Mercury’s mean density is the second-highest in the Solar System, which is estimated to be 5.427 g/cm3 – only slightly less than Earth’s density of 5.515 g/cm3.However, if the effects of gravitational compression – in which the effects of gravity reduce the size of an object and increases its density – then Mercury is in fact more dense than Earth, with an uncompressed density of 5.3 g/cm³ compared to Earth’s 4.4 g/cm³. These estimates can be also used to infer details of its inner structure. Compared to Earth, Mercury is much smaller, which is why it inner regions are subject to less in the way of compression. Therefore, its high density is believed to be the result of a large, and iron-rich core. All told, metals like iron and nickel are believed to make up 70% of the planet’s mass (higher than any other planet), while silicate rock accounts for just 30%. Internal structure of Mercury: 1. Crust: 100–300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius. Credit: MASA/JPL Several theories for this have been suggested, but the predominant one claims that Mercury had a thicker silicate crust earlier in its history. This crust was then largely blown off when a large planetesimal collided with the planet. Combined with its size and mass, Mercury has a surface gravity of 3.7 m/s2, which is the equivalent of 0.38 of Earth’s gravity (aka. 1 g). Density of Venus: The second planet from our Sun, as well as the second-closest terrestrial planet, Venus has a mean density of 5.243 g/cm3. Again, this is very close to Earth’s own density. And while much remains unknown about Venus’ geology and seismology, astronomers have an idea of Venus’ composition and structure based on comparative estimates of its size, mass and its density. In short, it is believed that Venus’ makeup and internal structure are very similar to Earth’s, consisting of a core, a mantle, and a crust. Also like Earth, the interior is though to be composed of iron-rich minerals, while silicate minerals make up the mantle and crust. The slightly smaller siz


What is the name given to the super dense stars that sometimes result form a supernova?

What is a Supernova – Definition & Facts of Star Explosion in Space – PlanetFacts.org Supernova What is a Supernova? To say in three words, a supernova is an exploding star. Okay, that was more than three, but you get the point. A supernova is more significant than a nova, but less so than a hypernova. Supernovae are very bright and generate bursts of radiation that can briefly outshine a whole galaxy before declining in brightness over many weeks or months. In this period a supernova can emit as much energy as the Sun might over its entire lifetime. How Supernovae are Studied By using optical telescopes, astronomers can approximate the amount of light generated by a supernova. These measurements can be used to determine how the luminosity and color of a supernova vary with time. Astronomers may examine the light through a prism, which breaks the light from a supernova into the spectrum of colors that composes it. From this, astronomers can gauge how the brightness of light depends on that light’s wavelength. The luminosity could change at all wavelengths. The spectrum of a supernova can very with time as well, until it fades entirely of course. The study of a supernova is more than just a study of any ordinary light show. Both the light and spectrum of color of a supernova can be used to make conclusions about the physics that occurs during and after supernova explosions. Understanding how a supernova explosion occurs and progresses is crucial to understanding why certain stars go boom. Supernovae are responsible for producing and dispersing elements into the interstellar medium. The elements that form stars, planets, and life on Earth are created and spread by supernovae. You could say that we are made of stardust. Naming Convention Supernovae are reported to the International Astronomical Union’s Central Bureau for Astronomical Telegrams, which assign them a name. The name begins with “SN”, the prefix for supernova, followed by the year, followed by a string of letter from A to Z. The first 26 supernovae are attached with a capital letter (A-Z). Following this are pairs of lower-case letters, such as aa, ab, ac, so on and so forth. For example the 367th supernova discovered in 2005 would be named SN 2005 nc. This naming convention was utilized since 1885. However, up until 1947, rarely would more than one supernova was found per year. Two-letter designations were scarcely necessary until 1987, and since 1988, they have been necessary more and more every year. Supernovae Types Since 1941, Rudolf Minkowski discovered that some spectra contain hydrogen and some do not, and therefore supernovae are classified by Type I, ones lacking hydrogen in their spectra, and Type II, ones that strongly show strong hydrogen lines. Since 1985, Type I supernovae have been classified further. Type Ia supernovae have a silicon spectral line at 615 nm, and Type Ib does not. Type Ib supernovae have strong helium lines, and Type Ic do not. Type I supernovae are classified such because of the sharp maxima and smooth decay of light in their light curves. The initiation of a Type I supernova can be modeled as an explosion of a carbon white dwarf that is crushed under the pressure of electron degeneracy. Supernovae Models The assumption follows that a white dwarf accumulates enough mass that it exceeds the Chandrasekhar limit of 1.4 solar masses (for white dwarves, this is the mass at which the star’s core can no longer resist gravitational collapse). The core temperature of the white dwarf rises dramatically, setting off chains of nuclear fusion reactions that essentially blow the star up. This model is consistent with the fact that Type I supernovae are hydrogen deficient, since white dwarves contain nearly zero hydrogen. Furthermore, the slow decay of light is consistent with the model, because the radioactive decay of unstable heavy elements produced by the supernova produces most of the energy. Supernovae of Type I can be further categorized into Types Ia, Ib, and Ic. Type Ia supernovae are indicated by the lack of


What shape is the Milky Way? - How the Milky Way Works | HowStuffWorks What shape is the Milky Way? Image courtesy NASA Edwin Hubble studied galaxies and classified them into various types of elliptical and spiral galaxies. The spiral galaxies were characterized by disk shapes with spiral arms. It stood to reason that because the Milky Way was disk-shaped and because spiral galaxies were disk-shaped, the Milky Way was probably a spiral galaxy. In the 1930s, astronomer R. J. Trumpler realized that the estimates of the size of the Milky Way galaxy by Kapetyn and others were off because the measurements had relied on observations in the visible wavelengths. Trumpler concluded that the vast amounts of dust in the plane of the Milky Way absorbed light in the visible wavelengths and caused faraway stars and clusters to appear dimmer than they actually were. Therefore, to accurately map stars and star clusters within the disk of the Milky Way, astronomers would need a way to peer through the dust. Up Next Could a planet exist without a host star? In the 1950s, the first radio telescopes were invented. Astronomers discovered that hydrogen atoms emitted radiation in the radio wavelengths and that these radio waves could penetrate the dust in the Milky Way. So, it became possible to map the spiral arms of the Milky Way. The key was marker stars like those used in distance measurements. Astronomers found that class O and B stars would work. These stars had several features: Brightness: They're highly visible and are often found in small groups or associations. Heat: They emit multiple wavelengths (visible, infrared, radio). Short life: They live for about 100 million years, so, considering the rate at which stars orbit the galaxy's center, they don't move far from where they were born. Astronomers could use radio telescopes to accurately map the positions of these O and B stars and use the Doppler shifts of the radio spectrum to determine their rates of motion. When they did this with many stars, they were able to produce combined radio and optical maps of the Milky Way's spiral arms. Each arm is named for the constellations that exist within it. Astronomers think that the motion of the material around the galactic center sets up density waves (areas of high and low density), much like you see when you stir cake batter with an electric mixer. These density waves are thought to cause the spiral nature of the galaxy. So, by examining the sky in multiple wavelengths (radio, infrared, visible, ultraviolet, X-ray ) with various ground-based and space-based telescopes, we can get different views of the Milky Way. On the next page we'll look into exactly what's inside the Milky Way. The Doppler Effect Much like the high-pitched sound from a fire-truck siren gets lower as the truck moves away, the movement of stars affects the wavelengths of light that we receive from them. This phenomenon is called the Doppler effect. We can measure the Doppler effect by measuring lines in a star's spectrum and comparing them to the spectrum of a standard lamp. The amount of the Doppler shift tells us how fast the star is moving relative to us. In addition, the direction of the Doppler shift can tell us the direction of the star's movement. If the spectrum of a star is shifted to the blue end, the star is moving toward us; if the spectrum is shifted to the red end, the star is moving away from us.


When was the first Pioneer space probe launched?

NASA - NSSDCA - Spacecraft - Details NSSDCA/COSPAR ID: 1958-007A Description Pioneer 1, the second and most successful of three project Able space probes and the first spacecraft launched by the newly formed NASA, was intended to study the ionizing radiation, cosmic rays, magnetic fields, and micrometeorites in the vicinity of the Earth and in lunar orbit. Due to a launch vehicle malfunction, the spacecraft attained only a ballistic trajectory and never reached the Moon. It did return data on the near-Earth space environment. Spacecraft and Subsystems Pioneer 1 consisted of a thin cylindrical midsection with a squat truncated cone frustrum on each side. The cylinder was 74 cm in diameter and the height from the top of one cone to the top of the opposite cone was 76 cm. Along the axis of the spacecraft and protruding from the end of the lower cone was an 11 kg solid propellant injection rocket and rocket case, which formed the main structural member of the spacecraft. Eight small low-thrust solid propellant velocity adjustment rockets were mounted on the end of the upper cone in a ring assembly which could be jettisoned after use. A magnetic dipole antenna also protruded from the top of the upper cone. The shell was composed of laminated plastic. The total mass of the spacecraft after vernier separation was 34.2 kg, after injection rocket firing it would have been 23.2 kg. The scientific instrument package had a mass of 17.8 kg and consisted of an image scanning infrared television system to study the Moon's surface to a resolution of 1 milliradian, an ionization chamber to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a spin-coil magnetometer to measure magnetic fields to 5 microgauss, and temperature-variable resistors to record spacecraft internal conditions. The spacecraft was powered by nickel-cadmium batteries for ignition of the rockets, silver cell batteries for the television system, and mercury batteries for the remaining circuits. Radio transmission was at on 108.06 MHz through an electric dipole antenna for telemetry and doppler information at 300 mW and a magnetic dipole antenna for the television system at 50 W. Ground commands were received through the electric dipole antenna at 115 MHz. The spacecraft was spin stabilized at 1.8 rps, the spin direction was approximately perpendicular to the geomagnetic meridian planes of the trajectory. Mission Profile The spacecraft did not reach the Moon as planned due to an incorrectly set valve in the upper stage which caused an accelerometer to give faulty information leading to a slight error in burnout velocity (the Thor second stage shut down 10 seconds early) and angle (3.5 degrees). This resulted in a ballistic trajectory with a peak altitude of 113,800 km around 1300 local time. The real-time transmission was obtained for about 75% of the flight, but the percentage of data recorded for each experiment was variable. Except for the first hour of flight, the signal to noise ratio was good. The spacecraft ended transmission when it reentered the Earth's atmosphere after 43 hours of flight on October 13, 1958 at 03:46 UT over the South Pacific Ocean. A small quantity of useful scientific information was returned, showing the radiation surrounding Earth was in the form of bands and measuring the extent of the bands, mapping the total ionizing flux, making the first observations of hydromagnetic oscillations of the magnetic field, and taking the first measurements of the density of micrometeorites and the interplanetary magnetic field. Alternate Names Launch Site: Cape Canaveral, United States Mass: 34.2 kg Department of Defense-Department of the Air Force (United States) NASA-Office of Space Science Applications (United States) Disciplines


Which planet id named after the sky-god who was father of the Titans?

Planetary Names: Planet and Satellite Names and Discoverers International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN) Planetary Names: Planet and Satellite Names and Discoverers Home Named Mercurius by the Romans because it appears to move so swiftly.   Discoverer Venus Roman name for the goddess of love. This planet was considered to be the brightest and most beautiful planet or star in the heavens. Other civilizations have named it for their god or goddess of love/war.   Discoverer Earth The name Earth comes from the Indo-European base 'er,'which produced the Germanic noun 'ertho,' and ultimately German 'erde,' Dutch 'aarde,' Scandinavian 'jord,' and English 'earth.' Related forms include Greek 'eraze,' meaning 'on the ground,' and Welsh 'erw,' meaning 'a piece of land.'     Earth I (Moon) Every civilization has had a name for the satellite of Earth that is known, in English, as the Moon. The Moon is known as Luna in Italian, Latin, and Spanish, as Lune in French, as Mond in German, and as Selene in Greek.     Martian System The names of the moons of Mars and the English translations of the names were specifically proposed by their discoverer, Asaph Hall, and as such, they have been accepted and retained under the current IAU nomenclature. Body Discoverer Mars Named by the Romans for their god of war because of its red, bloodlike color. Other civilizations also named this planet from this attribute; for example, the Egyptians named it "Her Desher," meaning "the red one."     Mars I (Phobos) Inner satellite of Mars. Named for one of the horses that drew Mars' chariot; also called an "attendant" or "son" of Mars, according to chapter 15, line 119 of Homer's "Iliad." This Greek word means "flight." August 17, 1877 A. Hall Mars II (Deimos) This outer Martian satellite was named for one of the horses that drew Mars' chariot; also called an "attendant" or "son" of Mars, according to chapter 15, line 119 of Homer's "Iliad." Deimos means "fear" in Greek. August 11, 1877 Selected Asteroids (of the Main Belt) and their Satellites Body Named for the Greek god of love. August 13, 1898 Named for a resort on the Crimean Peninsula. July 30, 1916 G. Neujmin (243) Ida Named for a nymph who raised the infant Zeus. Ida is also the name of a mountain on the island of Crete, the location of the cave where Zeus was reared. September 29, 1884 J. Palisa (243) Ida I (Dactyl) Named for a group of mythological beings who lived on Mount Ida, where the infant Zeus was hidden and raised (according to some accounts) by the nymph Ida. August 28, 1993 Galileo imaging and infrared science teams. (253) Mathilde The name was suggested by a staff member of the Paris Observatory who first computed an orbit for Mathilde. The name is thought to honor the wife of the vice director of the Paris Observatory at that time. November 12, 1885 J. Palisa (22) Kalliope I (Linus) Satellite of (22) Kalliope. In various accounts of Greek mythology, Linus is considered to be the son of the Muse Kalliope and the inventor of melody and rhythm. August 29 and September 2, 2001 Mauna Kea J.-L. Margot, M.E. Brown, W.J. Merline, F. Menard, L. Close, C. Dumas, C.R. Chapman, and D.C. Slater (45) Eugenia I (Petit-Prince) Satellite of (45) Eugenia. The Little Prince, Napolean-Eugene-Louis-Jean-Joseph Bonaparte (1856-1879), was the son of Eugenia de Montijo de Guzm\'an and Napoleon III. November 1, 1998 Mauna Kea W.J. Merline, L. Close, C. Dumas, C.R. Chapman, F. Roddier, F. Menard, D.C. Slater, G. Duvert, C. Shelton, and T. Morgan Jovian System Satellites in the Jovian system are named for Zeus/Jupiter's lovers and descendants. Names of outer satellites with a prograde orbit generally end with the letter "a" (although an "o" ending has been reserved for some unusual cases), and names of satellites with a retrograde orbit end with an "e." Body Discoverer Jupiter The largest and most massive of the planets was named Zeus by the Greeks and Jupiter by the Romans; he was the most important deity in both pantheons.     Jupiter I (Io) Io, the daughter


Visible sunspots vary in number according to a cycle of how many years?

Sunspots: Modern Research 4 of 7 The Sunspot Cycle Cycles have been around In the last few decades, we've started to understand the forces behind sunspots, but we've known for over a 150 years that sunspots appear in cycles. The average number of visible sunspots varies over time, increasing    and decreasing on a regular cycle of between 9.5 to 11 years, on average about 10.8    years. An amateur astronomer named Heinrich Schwabe, was the first to note this cycle, in 1843. The part of the    cycle with low sunspot activity is referred to as " solar minimum " while the portion of the cycle with high activity is known    as " solar maximum ." In fact they go around twice By studying the sun's magnetic field, modern astronomers have discovered that the cycle covers twenty-two years,    with each eleven-year cycle of sunspots followed by a reversal of the direction of the Sun's magnetic field. According to Fisher, "the overall magnetic field structure changes in a way that is very interesting. It turns    out that if the magnetic fields primarily point from west to east in the Northern Hemisphere (of the sun), they    point from east to west in the Southern Hemisphere. In the next eleven-year cycle, the fields are reversed. So    the cycle is really twenty-two years." Migration Sunspots appear mostly in the low latitudes near the solar equator. In fact they almost never appear closer than    5 or further than 40 degrees latitude, north or south. As each sunspot cycle progresses, the sunspots gradually start to appear closer and closer to the equator. The sunspot locations for the most recent 11-year cycle are shown    in this "butterfly" diagram." The locations "migrated" toward the equator (0 latitude)    from both hemispheres throughout this half of the cycle.   Do sunspots affect earth's climate? From 1645 to 1715, there was a drastically reduced number of sunspots. This period of reduced solar activity, which    was first noticed by G. Spörer, was later investigated by E.W. Maunder, is now called the Maunder            Minimum . That the same period of time was also unusually cold on            Earth.  Similar periods of low solar activity    seem to have occurred during the Spörer Minimum (1420-1530), the Wolf Minimum (1280-1340), and the Oort minimum    (1010-1050). This succession of low-temperature periods            is now called the "Little Ice Age," and the            corresponding pattern of extreme sunspot minima has led to speculation that sunspot activity may affect the earth's climate.


Which planet is usually the furthest form the Sun, but sometimes is not?

ASP: Pluto: The Farthest Planet (Usually) © 1988, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco,  CA 94112 Pluto:  The Farthest Planet (Usually) Pluto, the ninth  planet in our solar system, was not discovered until 1930 and remains a very  difficult world to observe because it's so far away. At an average distance  of 2.7 billion miles from the Earth, Pluto is a dim speck of light in even the  largest of our telescopes. It takes almost 249 years to make one swing around  the Sun, in a long looping orbit that takes it above and below the path of the  other planets. (See the accompanying box for more on its unusual path.) What  Would It Be Like on Pluto? While astronomers don't yet know many details about the landscape on Pluto, we do know that it's cold and dark out there. On average, Pluto is nearly 40 times as far from the Sun as we are. From that great distance, the Sun would look like a single, brilliant point of light (it would be only about 1/40th as big as the full Moon is in our sky — too small to appear as a disk.) During the day,  that tiny point illuminates the ground on Pluto with only 1/1500th the intensity  of sunlight we receive on Earth. (That's still far from being "dark,''  though: the Sun's light output as seen from Pluto is about 250 times the light  we receive from the Moon when it's full.) As you might expect, Pluto isn't warmed  much by the Sun; astronomers estimate its surface temperature to be more than  200 degrees below zero, Celsius. This is a temperature so cold that skin would  be as brittle as glass — and that some materials we're familiar with as gas  or Earth (such as methane) would freeze solid. New  Discoveries in the Last Decade Despite its great distance, Pluto has given up some of its secrets to careful study recently. Even though no spacecraft has investigated Pluto (and none is scheduled to), a happy circumstance is in part responsible for the accelerating pace of discoveries: Pluto is closer to us in the last two decades of the 20th century than it has been for the last 200 years (or will be for the next 200). Along with the great sensitivity and sophistication of today's astronomical instruments, this makes investigating Pluto from Earth less difficult now. In 1978, for example,  a relatively large satellite was discovered around Pluto and named Charon — and during the last half of the 1 980's, a rare alignment has made it possible  to study Pluto and Charon much more effectively than ever before. For a brief  period once every 124 years, observers on Earth are in a position to see Charon  pass directly in front of and behind Pluto in its 6.4-day orbit around the planet.  This "eclipse season'' began in 1985 and will end in 1990; there won't  be another one until the 22nd century — and not until the 23rd century  will one happen when Pluto is this close. By making careful measurements of  the eclipses, astronomers have made great progress in understanding the sometimes  strange and puzzling properties of Pluto and its satellite. Pluto  is Not the Ninth Planet Ever since 1930, school children have memorized the nine planets in order: Mercury, Venus, Earth, Mars, Jupiter Saturn, Uranus, Neptune, and PIuto. But between January, 1979 and March, 1999 that order is not correct. Pluto's eccentric (ellipse-shaped) orbit has brought it inside the orbit of Neptune, making it the eighth planet for two decades. Pluto's unusual position makes "What is the ninth planet?'' a great trivia question for a while. Just in case students  begin to worry that someday Pluto might collide with Neptune as the smaller  planet crosses the orbit of the larger, you can reassure them. The two orbits  are tilted relative to one another by 17 degrees) in such a way that  they never actually "touch.'' (Imagine two enormous, slightly elongated  hula hoops, one larger than the other. If the larger one is tilted relative  to the smaller one, you can imagine that the two points where the larger hoop  crosse


What was the name of the American mission to land a man on the Moon?

Apollo 11: First Men on the Moon Apollo 11: First Men on the Moon By Nola Taylor Redd, Space.com Contributor | July 25, 2012 03:39pm ET MORE Apollo 11 astronaut Edwin Aldrin photographed this iconic photo, a view of his footprint in the lunar soil, as part of an experiment to study the nature of lunar dust and the effects of pressure on the surface during the historic first manned moon landing in July 1969. Credit: NASA The historic launch of the Apollo 11 mission carried three astronauts toward the moon. Two of them would set foot on the lunar surface for the first time in human history as millions of people around the world followed their steps on television. The astronauts The crew of Apollo 11 were all experienced astronauts. All three had flown missions into space before. Cmdr. Neil Armstrong , 38, had previously piloted Gemini 8, the first time two vehicles docked in space. Born Aug. 5, 1930, in Ohio, Armstrong was 38 when he became the first civilian to command two American space missions. Apollo 11 crew: Neil Armstrong, Michael Collins and Edwin "Buzz" Aldrin. Credit: NASA Col. Edwin Eugene "Buzz" Aldrin , 39, was the first astronaut with a doctorate to fly in space. Born Jan. 20, 1930, in New Jersey, Aldrin piloted Gemini 12, taking a two-hour, twenty-minute walk in space to demonstrate that an astronaut could work efficiently outside of the vehicle. For Apollo 11, he served as the lunar module pilot. The command module pilot, Lt. Col. Michael Collins, 38, was born in Italy on Oct. 31, 1930. The pilot of Gemini 10, Collins spent almost an hour and a half outside of the craft on a space-walk and became the first person to meet another spacecraft in orbit. From Earth to the moon Mission planners at NASA studied the lunar surface for two years, searching for the best place to make the historic landing. Using high-resolution photographs taken by the Lunar Orbiter satellite and close-up photographs taken by the Surveyor spacecraft, they narrowed the initial thirty sites down to three. Influencing factors included the number of craters and boulders, few high cliffs or hills, and a relatively flat surface. The amount of sunlight was also a factor in determining the best time to land on the lunar surface. Apollo 11 launched from Kennedy Space Center in Florida at 9:32 a.m. EDT on July 16, 1969. While in flight, the crew made two televised broadcasts from the interior of the ship, and a third transmission as they drew closer to the moon, revealing the lunar surface and the intended approach path. On July 20, Armstrong and Aldrin entered the lunar module, nicknamed the "Eagle" and separated from the Command Service Module — the "Columbia" — headed toward the lunar surface. Apollo 11 astronaut Buzz Aldrin poses with the American flag on the surface of the moon in July 1969. Credit: NASA The lunar module touched down on the moon's Sea of Tranquility , a large basaltic region, at 4:17 p.m. EDT. Armstrong notified Houston with the historic words, "Houston, this is Tranquility Base. The Eagle has landed." For the first two hours, Armstrong and Aldrin checked all of the systems, configured the lunar module for the stay on the moon, and ate. They decided to skip the scheduled four-hour rest to explore the surface. A camera in the Eagle provided live coverage as Armstrong descended down a ladder at 11:56 p.m. on July 20, 1969, and uttered the words, "That's one small step for man, one giant leap for mankind." Aldrin followed twenty minutes later, with Armstrong recording his descent. Armstrong had the responsibility to document the landing, so most of the images taken from the Apollo 11 mission were of Aldrin. [Images: NASA's Historic Apollo 11 Moon Landing in Pictures ] While on the surface, the astronauts set up several experiments, collected samples of lunar soil and rock to bring home, erected a United States flag, and took core samples from the crust. They spoke with U.S. President Richard Nixon, whose voice was transmitted from the White House, and placed a plaque that stated: HERE MEN FROM THE PLANET EARTH FIRST SET FOOT


What was the name of the American space station?

Skylab: First U.S. Space Station Skylab: First U.S. Space Station By Elizabeth Howell, Space.com Contributor | February 1, 2013 06:40pm ET MORE The Skylab Orbital Workshop experienced a failure that led to a replacement shield to protect against solar heating. Credit: NASA. Skylab was the first space station operated by the United States. It spent six years orbiting Earth until its decaying orbit caused it to re-enter the atmosphere. It scattered debris over the Indian Ocean and sparsely settled areas of Western Australia. Three crews successfully lived on board the station for several months each. The last crew spent 84 days in orbit — an American record that stood until the shuttle era. [ Photos: Skylab, the 1st U.S. Space Station ] Rocky start Various NASA centers had kicked around ideas for a space station for years before Skylab launched. However, the agency was very focused on the space race and moonshots that dominated public consciousness in the 1960s. Money for other endeavors was not as available. As Apollo began to wind down in the early 1970s, NASA began an Apollo Applications Program to fly unused hardware from the moon program. One idea, proposed by famous Apollo rocket engineer Wernher von Braun , would be to build a space station out of an unused rocket stage. The design evolved over the years as NASA struggled with reduced funding. Skylab finally aimed for space on May 14, 1973. However, a meteoroid shield that was supposed to shelter Skylab accidentally opened about 63 seconds into the launch. The still-thick atmosphere tore the shield off, plunging Skylab into a serious situation. The facility experienced communications problems with the antenna as a result of the incident, but that was the least of the agency's worries. "When the meteoroid shield ripped loose, it disturbed the mounting of workshop solar array wing No. 2 and caused it to partially deploy. The exhaust plume of the second stage retro-rockets impacted the partially deployed solar array and literally blew it into space," NASA wrote. Workers at NASA's Marshall Space Flight Center scrambled to stabilize the station. Among other measures, they put the station in an attitude that would minimize overheating, and came up with ways to cope with the station's reduced power situation. Meanwhile, the first crew – led by Apollo 12 commander Pete Conrad – would need to make the station habitable before they could get to work. The crew's first challenge during the spacewalk, just hours after launch, was deploying the solar array, but initial attempts met with no luck as a metal strip holding it down refused to give way. Crew members emerged from an expected communications blackout in a foul mood, according to an official NASA account of the mission. "The astronauts were venting their frustration with four-letter words, while Houston repeatedly tried to remind them that communication had resumed," NASA wrote. Realizing the tools they had with them that day would not work, Conrad abandoned the exercise and focused on trying to dock his spacecraft with the station. Unfortunately, the docking mechanism failed and the crew had to depressurize the spacecraft and bypass electrical connections to achieve it. In subsequent days, Conrad's crew erected a sun shade , successfully deployed the stuck array, and began operational work aboard the station. While the incident was frustrating for the teams involved, it also demonstrated that it was possible to fix a badly damaged space station while it is in orbit. Cutaway view of Skylab


Which country built the Saturn V rocket?

Saturn V Launch Vehicle | National Air and Space Museum Saturn V Launch Vehicle Saturn V Launch Vehicle Saturn V Launch Vehicle The manned Apollo missions were each launched aboard a Saturn V launch vehicle. The "V" designation originates from the five powerful F-1 engines that powered the first stage of the rocket. The Saturn V remains the largest and most powerful U.S. expendable launch vehicle ever built. The Apollo spacecraft, including the Command Module (CM), Service Module (SM) and Lunar Module (LM) sat atop the launch vehicle. Above the CM was the emergency escape system. The complete assembly including the Apollo spacecraft and the Saturn launch vehicle stood 363 feet tall (110.6 meters) and weighed over 6 million pounds (2.7 million kg). The Saturn V launch vehicle itselft consisted of three stages: First Stage (S-IC): The first stage includes the five F-1 engines producing nearly 7.7 million pounds of thrust. These powerful engines are required to lift the heavy rocket fast enough to escape Earth's gravity. The first stage engines are burned at liftoff and last for about 2.5 minutes taking the vehicle and payload to an altitude of 38 miles. The first stage then separates and burns up in the Earth's atmosphere. Second Stage (S-II): The second stage conatins five J-2 engines. After the first stage is discarded, the second stage burns for approximately 6 minutes taking the vehicle and payload to 115 miles altitude. The second stage is then also discarded. Third Stage (S-IVB): The third stage contains one J-2 engine. This engine burns for 2.75 minutes boosting the spacecraft to orbital velocity of about 17,500 mph. The third stage is shut down with fuel remaining and remains attached the spacecraft in Earth orbit. The J-2 engine is reignited to propel the spacecraft into translunar trajectory (speed of 24,500 mph) before finally being discarded. Saturn V Rocket


Which objects in space emit energy in pulses?

Pulsars - Celestial Objects on Sea and Sky Pulsars Pulsars Cosmic Beacons Pulsars are among the strangest objects in the universe. In 1967, at the Cambridge Observatory, Jocelyn Bell and Anthony Hewish were studying the stars when they stumbled on something quite extraordinary. It was a star-like object that seemed to be emitting quick pulses of radio waves. Radio sources had been known to exist in space for quite some time. But this was the first time anything had been observed to give off such quick pulses. They were as regular as clockwork, pulsing once every second. The signal was originally thought to be coming from an orbiting satellite, but that idea was quickly disproved. After several more of these objects had been found, they were named pulsars because of their rapidly pulsing nature. Bright pulsars have been observed at almost every wavelength of light. Some can actually be seen in visible light. Many people tend to get pulsars confused with quasars. But the two objects are totally different. Quasars are objects that produce enormous amounts of energy and may be the result of a massive black hole at the center of a young galaxy. But a pulsar is a different animal entirely. The Lighthouse Effect A pulsar is basically a rapidly spinning neutron star. A neutron star is the highly compacted core of a dead star, left behind in a supernova explosion. This neutron star has a powerful magnetic field. In fact, this magnetic field is about one trillion times as powerful as the magnetic field of the Earth. The magnetic field causes the neutron star to emit strong radio waves and radioactive particles from its north and south poles. These particles can include a variety of radiation, including visible light. Pulsars that emit powerful gamma rays are known as gamma ray pulsars. If the neutron star happens to be aligned so that the poles face the Earth, we see the radio waves every time one of the poles rotates into our line of sight. It is a similar effect as that of a lighthouse. As the lighthouse rotates, its light appears to a stationary observer to blink on and off. In the same way, the pulsar appears to be blinking as its rotating poles sweep past the Earth. Different pulsars pulse at different rates, depending on the size and mass of the neutron star. Sometimes a pulsar may have a binary companion. In some cases, the pulsar may begin to draw in matter from this companion. this can cause the pulsar to rotate even faster. The fastest pulsars can pulse at well over a hundred times a second. Pulsars & Neutron Stars A pulsar is formed when a massive star collapses exhausts its supply of fuel. It blasts out in a giant explosion known as a supernova, the most powerful and violent event in the universe. Without the opposing force of nuclear fusion to balance it, gravity begins to pull the mass of the star inward until it implodes. In a pulsar, gravity compacts the mass of the star until it forms an object composed primarily of neutrons packed so tightly that they no longer exist as normal matter. A physicist named Chandrasekhar Subrahmanyan theorized that if the mass of the core of the collapsing star was 1.4 times the mass of the star itself, the protons and electrons would combine to form neutrons in a neutron star. This number is known today as the Chandrasekhar limit. If this limit is not achieved by the collapsing core, a white dwarf star will be produced instead. If the limit is much greater, a black hole may be the result. As the star collapses, it begins to spin more rapidly in what is known as the conservation of angular momentum. The process is similar to that of an ice skater pulling their arms in close to spin faster. What is left behind is a rapidly spinning ball of tightly packed neutrons inside an iron shell. The extreme force of gravity would cause this shell to be extremely smooth and shiny. The resulting neutron star is only about 20 miles in diameter, yet is contains most of the mass of the original star it was formed from. The matter in this neutron star is packed so tightly that a piece the size of a sug


What travels around the Sun at an average speed of 185 miles per second.

At what speed does the Earth move around the Sun? (Beginner) - Curious About Astronomy? Ask an Astronomer At what speed does the Earth move around the Sun? (Beginner) Short version: Earth's average orbital speed is about 30 kilometers per second. In other units, that's about 19 miles per second, or 67,000 miles per hour, or 110,000 kilometers per hour (110 million meters per hour). In more detail: Let's calculate that. First of all we know that in general, the distance you travel equals the speed at which you travel multiplied by the time (duration) of travel. If we reverse that, we get that the average speed is equal to the distance traveled over the time taken. We also know that the time it takes for the Earth to go once around the Sun is one year. So, in order to know the speed, we just have to figure out the distance traveled by the Earth when it goes once around the Sun. To do that we will assume that the orbit of the Earth is circular (which is not exactly right, it is more like an ellipse , but for our purpose a circle is close enough). So the distance traveled in one year is just the circumference of the circle. (Remember, the circumference of a circle is equal to 2×π×radius.) The average distance from the Earth to the Sun is about 149,600,000 km. (Astronomers call this an astronomical unit, or AU for short.) Therefore, in one year, the Earth travels a distance of 2×π×(149,600,000 km). This means that the speed is about: speed = 2×π×(149,600,000 km)/(1 year) and if we convert that to more meaningful units (knowing that there are, on average, about 365.25 days in a year, and 24 hours per day) we get: speed = 107,000 km/h (or, if you prefer, 67,000 miles per hour) So the Earth moves at about 110,000 km/h around the Sun (which is about one thousand times faster than the typical speed of a car on a highway!) Thanks for your explanation, but I was hoping for an explanation a little more precise, since I already knew the one you gave. In the case of your question about the speed of the Earth around the Sun, there isn't really a more 'precise' answer. The only approximation I did in the calculation I sent you is assuming that the orbit of the Earth is circular. This is in fact a very good approximation. One of Kepler's laws describing planetary motions states that all orbits are ellipses. This is the case for Earth's orbit. But not all ellipses come in the same shape. They are described by their 'eccentricity', which tells us how flattened they are. The eccentricity  of an ellipse is a number that varies between 0 and 1, 0 being a perfect circle, and close to 1 being a very flattened ellipse. It turns out that the orbit of the Earth right now has an eccentricity of about 0.017. This means it is almost a circle, making our approximation valid. So under the one approximation that was made, the calculation couldn't really be more 'precise'. And as for the average Earth-Sun distance, the true value changes slightly over time due to gravitational perturbations from the other planets, so there really isn't much point in using a more precise value than the one given above. Now if you want to calculate the speed of the Earth on its orbit without assuming it is a circle, it is another ball game! First of all, I cannot give you a precise answer, because the speed of the Earth changes all the time as the Earth moves around the Sun. This is because Kepler's second law says that on its orbit, a planet will sweep equal areas in equal amounts of time. This means that when the Earth is closer to the Sun (which happens in early January, about two weeks after the northern winter solstice) it's moving faster than when it is farther away. (For more information on how the Earth's orbital speed varies over the course of a year, please see this answer .) Unless you specified a certain date, this means I cannot give you a precise value for the speed of the Earth assuming its orbit is an ellipse. We are better off to stick with the first number we got - the average speed. I hope this answers your question now! This page was last updated on Febr


Which is the second lightest element in the universe?

Where is Helium Found - Universe Today   Universe Today by Tega Jessa [/caption] Helium is the second lightest element in the known universe. It is also the second most abundant. According to some estimates helium accounts for as much as 24 percent of the Universe’s mass. This element is also plentiful since it is a prime product of fusion nuclear reactions involving hydrogen. So if it is so plentiful where is Helium found? The problem is that just because an element is common in the universe at large does not mean that it is common on Earth. Helium is an element that fits this scenario. Helium only accounts for 0.00052% of the Earth’s atmosphere and the majority of the helium harvested comes from beneath the ground being extracted from minerals or tapped gas deposits. This makes it one of the rarest elements of any form on the planet. Like mentioned before Helium is rare on Earth but there are places where it is readily found. If you look at space the majority of helium is in stars and the interstellar medium. This is due to the fusion reaction that powers most stars fusing single hydrogen atoms to create helium atoms. This process balanced with a star’s gravity is what helps it to stay stable for billions of years. On Earth the majority of helium found comes from radioactive decay. This is the opposite nuclear reaction called fission that splits atoms. For this reason radioactive minerals in the lithosphere like uranium are prime sources for helium. On Earth there are key locations where concentrated helium can be harvested. The United States produces the majority of the world’s helium supply at 78%. The rest of the world’s helium is harvested in North Africa, The Middle East, and Russia. The interesting thing is that thanks to these deposits the world’s demand for helium is being met regularly. Also unlike petroleum which can decades to form from organic material, 3000 metric tons of Hydrogen is produced yearly. Until helium demand reaches at least the same level of demand as petroleum there it little chance of that demand outpacing supply. Helium is looking to be a major player in the near future. Governments are looking into using the gas as source of hydrogen for fuel cells and other transportation technologies. At the moment the promise is still tentative but at least with better surveying and knowledge of gas deposits there will be a supply waiting if becomes the next major element to power human civilization. In the meanwhile ours is still a planet beholden to carbon. We have written many articles about Helium for Universe Today. Here’s an article about the discovery of Helium , and here’s an article about composition of the Sun . If you’d like more info about helium on Earth, check out NASA’s Solar System Exploration Guide on Earth . And here’s a link to NASA’s Earth Observatory . We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth .


What is the name of the thousands of small bodies which orbit the Sun?

Small Solar-System Bodies  l Small Bodies News Small Solar-System Bodies The title The Nine Planets is somewhat misleading. In addition to the (eight) planets and their satellites the solar system contains a large number of smaller but interesting objects. Small Bodies There are thousands of known asteroids and comets and undoubtedly many more unknown ones. Most asteroids orbit between Mars and Jupiter . A few (e.g. 2060 Chiron) are farther out. There are also some asteroids whose orbits carry them closer to the Sun than the Earth (Aten, Icarus, Hephaistos). Most comets have highly elliptical orbits which spend most of their time in the outer reaches of the solar system with only brief passages close to the Sun. And there is a large and important class of Trans-Neptunian Objects or Kuiper Belt Objects (including Pluto) that orbit (mostly) beyond Neptune. The distinction between comets and asteroids is somewhat controversial . The main distinction seems to be that comets have more volatiles and more elliptical orbits. But there are interesting ambiguous cases such as 2060 Chiron (aka 95 P/Chiron) and 3200 Phaethon which seem to share some aspects of both categories. Asteroids are sometimes also referred to as minor planets or planetoids (not to be confused with "lesser planets" which refers to Mercury and Pluto ). Some of the largest asteroids and Kuiper Belt objects may be classified as dwarf planets. Very small rocks orbiting the Sun are sometimes called meteoroids to distinguish them from the larger asteroids. When such a body enters the Earth's atmosphere it is heated to incandescence and the visible streak in the sky is known as a meteor. If a piece of it survives to reach the Earth's surface it is known as a meteorite. Millions of meteors bright enough to see strike the Earth every day (amounting to hundreds of tons of material). All but a tiny fraction burn up in the atmosphere before reaching the ground. The few that don't are our major source of physical information about the rest of the solar system. Finally, the space between the planets is not empty at all. It contains a great deal of microscopic dust and gas as well as radiation and magnetic fields.


What can contract to give birth to a star?

Stars | Science Mission Directorate Science Mission Directorate Exoplanets Stars Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy. Star Formation Stars are born within the clouds of dust and scattered throughout most galaxies. A familiar example of such as a dust cloud is the Orion Nebula. Turbulence deep within these clouds gives rise to knots with sufficient mass that the gas and dust can begin to collapse under its own gravitational attraction. As the cloud collapses, the material at the center begins to heat up. Known as a protostar, it is this hot core at the heart of the collapsing cloud that will one day become a star. Three-dimensional computer models of star formation predict that the spinning clouds of collapsing gas and dust may break up into two or three blobs; this would explain why the majority the stars in the Milky Way are paired or in groups of multiple stars. The observations of Eta Carinae's light echo are providing new insight into the behavior of powerful massive stars on the brink of detonation. Credit: NOAO, AURA, NSF, and N. Smith (University of Arizona) As the cloud collapses, a dense, hot core forms and begins gathering dust and gas. Not all of this material ends up as part of a star — the remaining dust can become planets, asteroids, or comets or may remain as dust. In some cases, the cloud may not collapse at a steady pace. In January 2004, an amateur astronomer, James McNeil, discovered a small nebula that appeared unexpectedly near the nebula Messier 78, in the constellation of Orion. When observers around the world pointed their instruments at McNeil's Nebula , they found something interesting — its brightness appears to vary. Observations with NASA's Chandra X-ray Observatory provided a likely explanation: the interaction between the young star's magnetic field and the surrounding gas causes episodic increases in brightness. Main Sequence Stars A star the size of our Sun requires about 50 million years to mature from the beginning of the collapse to adulthood. Our Sun will stay in this mature phase (on the main sequence as shown in the Hertzsprung-Russell Diagram) for approximately 10 billion years. Stars are fueled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight, and the energy by which it shines. As shown in the Hertzsprung-Russell Diagram, Main Sequence stars span a wide range of luminosities and colors, and can be classified according to those characteristics. The smallest stars, known as red dwarfs, may contain as little as 10% the mass of the Sun and emit only 0.01% as much energy, glowing feebly at temperatures between 3000-4000K. Despite their diminutive nature, red dwarfs are by far the most numerous stars in the Universe and have lifespans of tens of billions of years. On the other hand, the most massive stars, known as hypergiants, may be 100 or more times more massive than the Sun, and have surface temperatures of more than 30,000 K. Hypergiants emit hundreds of thousands of times more energy than the Sun, but have lifetimes of only a few million years. Although extreme stars such as these are believed to have been common in the early Universe, today they are extremely rare - the entire Milky Way galaxy contains only a handful of hypergiants. Stars and Their Fates In general, the larger a star, the shorter its life, although all but the most massive stars live for billions o


What is the name for the study of the structure of the universe?

WMAP's Introduction to Cosmology Related Topics Cosmology: The Study of the Universe Cosmology is the scientific study of the large scale properties of the universe as a whole. It endeavors to use the scientific method to understand the origin, evolution and ultimate fate of the entire Universe. Like any field of science, cosmology involves the formation of theories or hypotheses about the universe which make specific predictions for phenomena that can be tested with observations. Depending on the outcome of the observations, the theories will need to be abandoned, revised or extended to accommodate the data. The prevailing theory about the origin and evolution of our Universe is the so-called Big Bang theory. Choose from the links in the left column for discussed at length. This primer in cosmological concepts is organized as follows: The main concepts of the Big Bang theory are introduced in the first section with scant regard to actual observations. The second section discusses the classic tests of the Big Bang theory that make it so compelling as the most likely valid and accurate description of our universe. The third section discusses observations that highlight limitations of the Big Bang theory and point to a more detailed model of cosmology than the Big Bang theory alone provides. As discussed in the first section, the Big Bang theory predicts a range of possibilities for the structure and evolution of the universe. The final section discusses what constraints we can place on the nature of our universe based on current data, and indicates how WMAP furthers our understanding of cosmology. In addition, a few related topics are discussed based on commmonly asked questions. For purposed of citation of this portion of the site or the downloadable PDF you can use this information: WMAP Science Team, "Cosmology: The Study of the Universe," NASA's Wilkinson Microwave Anisotropy Probe,last modified June 6, 2011, http://map.gsfc.nasa.gov/universe/WMAP_Universe.pdf or http://map.gsfc.nasa.gov/universe/


What units are used for measuring distances in the universe?

Units for Distance and Size in the Universe | Las Cumbres Observatory Space Book Units for Distance and Size in the Universe Astronomers use many of the same units of measurement as other scientists. They often use meters for length, kilograms for mass, and seconds for time. However, the distances and sizes in the universe can be so big, that astronomers have invented more units to describe distance. Astronomical Units: Distances in the solar system are often measured in astronomical units (abbreviated AU). An astronomical unit is the average distance between the Earth and the Sun: 1 AU = 1.496 × 108 km = 93 million miles Jupiter is about 5.2 AU from the Sun and Pluto is about 39.5 AU from the Sun. The distance from the Sun to the center of the Milky Way is approximately 1.7 × 109 AU. Light-Years: To measure the distances between stars, astronomers often use light-years (abbreviated ly). A light-year is the distance that light travels in a vacuum in one year: 1 ly = 9.5 × 1012 km = 63,240 AU Proxima Centauri is the nearest star to Earth (other than the Sun) and is 4.2 light-years away. This means light from Proxima Centauri takes 4.2 years to travel to Earth. Parsecs: Many astronomers prefer to use parsecs (abbreviated pc) to measure distance to stars. This is because its definition is closely related to a method of measuring the distances between stars. A parsec is the distance at which 1 AU subtends and angle of 1 arcsec. 1 pc = 3.09 × 1013 km = 3.26 ly    For even greater distances, astronomers use kiloparsecs and megaparsecs (abbreviated kpc and Mpc). 1 kiloparsec = 1 kpc = 1000 pc = 103 pc 1 megaparsec = 1 Mpc = 1,000,000 pc = 106 pc Powers of Ten: The distances and sizes of of the objects astronomers study vary from very small, including atoms and atomic nuclei, to very large including galaxies, clusters of galaxies and the size of the universe. To describe such a huge range, astronomers need a way to avoid confusing terms like "a billion trillion" and "a millionth". Astronomers use a system called powers-of-ten notation, which consolidates all of the zeros that you would normally find attached to very large or small numbers such as 1,000,000,000,000 or 0.0000000001. All of the zeros are put in an exponent, which is written as a superscript, and indicates how many zeros you would need to write out the long form of the number. So for example: 100 = 1 104 = 10,000 and so on. In powers-of-ten notation, numbers are written as a figure between one and ten multiplied by a power of ten. So for example, the distance to the Moon of 384,000 km can be re-written as 3.84 × 105 km. Notice that 3.84 is between one and ten. The same number could accurately be rewritten as 38.4 × 104 or 0.384 × 106, but the preferred form is to have the first number be between one and ten. Very small numbers can also be written using powers-of-ten notation. The exponent is negative for numbers less than one and indicates dividing by that number of tens. So for example: 100 = 1


What is another name for a shooting or falling star?

What is a Shooting Star? - Universe Today   Universe Today What is a Shooting Star? Article Updated: 24 Dec , 2015 by Fraser Cain A shooting star is another name for a meteoroid that burns up as it passes through the Earth’s atmosphere. So, a shooting star isn’t a star at all. Most of the shooting stars that we can see are known as meteoroids. These are objects as small as a piece of sand, and as large as a boulder. Smaller than a piece of sand, and astronomers call them interplanetary dust. If they’re larger than a boulder, astronomers call them asteroids. A meteoroid becomes a meteor when it strikes the atmosphere and leaves a bright tail behind it. The bright line that we see in the sky is caused by the ram pressure of the meteoroid. It’s not actually caused by friction, as most people think. When a meteoroid is larger, the streak in the sky is called a fireball or bolide. These can be bright, and leave a streak in the sky that can last for more than a minute. Some are so large they even make crackling noises as they pass through the atmosphere. If any portion of the meteoroid actually survives its passage through the atmosphere, astronomers call them meteorites. Some of the brightest and most popular meteor showers are the Leonids, the Geminids, and the Perseids. With some of these showers, you can see more than one meteor (or shooting star) each minute.


What is the Latin name for the North Star?

North Star - definition of North Star by The Free Dictionary North Star - definition of North Star by The Free Dictionary http://www.thefreedictionary.com/North+Star (Celestial Objects) the North Star another name for Polaris 1 Po•lar•is (poʊˈlɛər ɪs, -ˈlær-, pə-) n. the polestar or North Star, a star of the second magnitude situated close to the north pole of the heavens, in the constellation Ursa Minor: the outermost star in the handle of the Little Dipper. [1955–60; short for Medieval Latin stella polāris polar star] North Star Noun 1. North Star - the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it polar star , Polaris , pole star , polestar Little Bear , Ursa Minor - a constellation outside the zodiac that rotates around the North Star Little Dipper , Dipper - a cluster of seven stars in Ursa Minor; at the end of the dipper's handle is Polaris North Star noun Pole Star , Polaris , lodestar I could see the Bear and had identified the North Star. Translations North Star n the North Star → la stella polare Want to thank TFD for its existence? Tell a friend about us , add a link to this page, or visit the webmaster's page for free fun content . Link to this page: References in classic literature ? He pointed to where the North Star burned over the Khyber Pass. Little Mildred answered nothing, but watched the North Star and hummed a selection from recent Simla burlesque that had much delighted the White Hussars. View in context said the scout, shaking his head doubtingly; "When the sun is scorching the tree tops, and the water courses are full; when the moss on every beech he sees will tell him in what quarter the north star will shine at night. View in context And first, as soon as it began to be dark, we kindled a fire in our little camp, which we kept burning, and prepared so as to make it burn all night, that the Tartars might conclude we were still there; but as soon as it was dark, and we could see the stars (for our guide would not stir before), having all our horses and camels ready loaded, we followed our new guide, who I soon found steered himself by the north star, the country being level for a long way. 'Living wage' is helping The acquisition underscores [our] continued commitment to providing quality service and high quality block, brick, landscape, and contractor supply products to the southern Minnesota and northern Iowa markets," says North Star Regional Manager Chad Grande. Already a key source of clay brick, concrete block and retaining wall units, natural stone veneers and landscaping materials, North Star Stone & Masonry has extended its southern Minnesota footprint by acquiring the Superior Concrete Block Co. plant in Mankato, southwest of the Twin Cities North Star is gratified that the Board has made a change of the Chairman position, but this change falls far short of addressing the pro-shareholder corporate governance initiatives North Star has continuously sought, including elimination of the classified board and adding shareholder nominated directors to the Board.


Scientists study the red shift to investigate which aspect of cosmology?

An Introduction to Philosophy and Cosmology What is Cosmology? written by: Jason C. Chavis•edited by: RC Davison •updated: 7/30/2011 Cosmology is the study of the Universe and man's place within it. Human existence is intertwined with the understanding and existence of the Universe. Cosmology attempts to analyze this connection between what we know to be true and what we believe in. Science, religion and philosophy play a role. slide 1 of 7 How Cosmology Fits with Science Cosmology is the study of the Universe and humanity's place within it. The study has a long history, rooted in region, science, philosophy and esotericism. The first use of the definition was by Christian Wolff, a German philosopher who wrote Comologia Generalis in 1730. The term is derived from the Greek kosmos, meaning “universe," and logia, meaning “study." Modern cosmology is an extension of physics and astrophysics. As the studies showed to play a central role in the fundamental understanding of the Universe, the two sciences became synonymous with cosmology . Mathematics and observational elements began to define the limits and expanses of the Universe as a whole. Scientist were able to understand the concept of the big bang and hypothesize about the expansion of space, determining that the Universe formed 13.7 billion years ago. These discoveries led to the establishment of certain physical laws that exist today, and logically have always existed. Roger Bacon, persecuted by the Catholic Church, postulated during the 1200s the idea of a universe not centered around humans. This drew a stark contrast between religion and science. Cosmology attempts to not only decipher the true nature of the Universe, but also man's place within its boundaries. This has led to the creation of a specific discipline within the cosmology field known as metaphysical cosmology. It attempts to answer the questions regarding natural boundaries and where the human being lies. It can also make determinations about God as a concept within the spacial construct of the Universe. Ancient religions were tandem to the early studies of cosmology. Mythologizing and theorizing about the creation of the Universe, man's place and the ultimate destruction. slide 2 of 7 slide 3 of 7 Above: Ancient woodcarving of where heaven and earth meet. (Image credit: Heikenwaelder Hugo at Wikimedia Commons, http://en.wikipedia.org/wiki/File:Universum.jpg, Creative Commons Attribution ShareAlike 2.5.) slide 4 of 7 Science The establishment of the large scale nature of the Universe was one of the first successes of the early cosmologists. Ptolemy, an ancient Greek mathematician, proposed the theory that the Earth was the center of the Universe and all things flow around it. This model was called the geocentric system and stayed as the preferred truth about the Universe until the 16th century. Nicolaus Copernicus authored a book entitled On the Evolution of Celestial Spheres in which he claimed the Earth was not the center of the Universe and it orbited around the Sun. This made the Sun the center of the Universe and this was called the heliocentric system. Subsequent studies made by Johannes Kepler and Galileo Galilei also supported this theory. However, critics of this idea questioned why the celestial bodies floated around the Sun. It wasn't until Isaac Newton established the law of universal gravitation that humans understood the principles that made the solar system function -- gravity was the cause of all motion. During the 1900s, scientists like Albert Einstein pushed for greater understanding of the Universe. The Great Debate, a meeting of the U.S. National Academy of Sciences in Washington on August 26, 1920, established the modern principles that scientists follow today. The center of the debate was whether the Milky Way star system was the only true system and everything else orbited around it. Harlow Wilson was the champion of this theory, while Herber D. Curtis claimed that spiral nebulae were their own system, essentially island universes. Edwin Hubble solved the question by showing that


Which planet possesses the Galilean satellites?

Photos: The Galilean Moons of Jupiter Photos: The Galilean Moons of Jupiter By SPACE.com | June 14, 2013 06:49am ET MORE Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Introduction 67 moons orbit the great gas giant Jupiter; of these, the four largest are known as the Galilean moons, having been discovered by Galileo Galilei using his telescope in 1610. The four moons are Io, Europa, Ganymede, and Callisto, in order of distance from Jupiter. (Their names derive from lovers of Zeus.) These moons provided evidence that not all celestial bodies orbit the Earth, a powerful revelation as, up until that time, astronomers considered Earth the center of the universe. [See Jupiter’s Moons reference page for more information.] First: Io Credit: NASA/JPL/University of Arizona Io Io orbits closest to Jupiter, out of the four Galilean moons. Io has been studied by spacecraft from Pioneer 10 and 11 in 1973 and 1974, all the way up to New Horizons in 2007, augmented by Earth- and space-based telescopes. This satellite possesses volcanoes, the only celestial body in the solar system other than Earth known to harbor volcanic activity. In fact, Io represents the most geologically active object in the solar system. Io contains an iron or iron sulfide core and a brown silicate outer layer, producing colorful orange, yellow, black, red, and white patches on the surface. Io also possesses sulfur dioxide snowfields, covering much of its surface. [See more information about Io .] Next: Europa Credit: NASA/JPL/University of Arizona Europa Europa, slightly smaller than Earth’s moon, represents one of the largest bodies in the solar system, though smaller than the other Galilean satellites of Jupiter. Cracks and streaks mark the entirety of the icy surface, which contains few craters, as the shiny, smooth skin of the moon only dates back 20 to 180 million years, a youthful age. Researchers speculate that a liquid water ocean lies beneath the ice. [See more information about Europa .] Next: Ganymede Credit: NASA Ganymede Ganymede, the third Gallilean moon, looms larger than the others. It compares in size to Mercury, but possesses about half the mass of that planet. Ganymede distinguishes itself from the other Galilean moons by possessing its own magnetic field. A thick crust of mostly ice wraps around the satellite’s iron core. Highly cratered dark regions cover 40 percent of Ganymede’s surface, while the remaining 60 percent hosts a light grooved terrain, forming intricate patterns on that moon. [See more information about Ganymede .] Next: Callisto Credit: NASA Callisto Callisto, the fourth Galilean moon, farthest from Jupiter, represents the most heavily cratered object in the solar system. The moon’s landscape remains largely unchanged since the time of its formation, attracting much interest from researchers. Callisto roughly approximates Mercury in size, but the moon possesses a lower density. It also experiences the least amount of effect from Jupiter’s magnetic field, as it orbits farther away from the planet, beyond Jupiter’s primary radiation belt. [See more information about Callisto .] 6 of 6


What is brighter than a hundred million suns?

Brighter Than 200 Million Suns Imagining and Planning Interstellar Exploration Brighter Than 200 Million Suns by Paul Gilster on September 2, 2004 It looks bright enough to be a foreground star, but this supernova, called SN 2004dj, is 11 million light years away in a galaxy known as NGC 2403. Not particularly germane to interstellar propulsion or finding candidates for robotic probes, but simply too remarkable a sight to ignore. You can read more about this Hubble photograph here . From the press release issued by the Space Telescope Science Institute: The heart of NGC 2403 is the glowing region at lower left. Sprinkled across the region are pink areas of star birth. The myriad of faint stars visible in the Hubble image belong to NGC 2403, but the handful of very bright stars in the image belong to our own Milky Way Galaxy and are only a few hundred to a few thousand light-years away. This image was taken on Aug. 17, two weeks after an amateur astronomer discovered the supernova. What we’re seeing here is the creation of heavy chemical elements like calcium, iron and gold, all of which, on Earth and elsewhere, came from explosions like this one. Charter In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last nine years, this site has coordinated its efforts with the Tau Zero Foundation , and now serves as the Foundation's news forum. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi ). Now Reading


How many rings does Saturn have? | Cool Cosmos   How many rings does Saturn have? Saturn has four main groups of rings and three fainter, narrower ring groups. These groups are separated by gaps called divisions. Close up views of Saturn's rings by the Voyager spacecrafts, which flew by them in 1980 and 1981, showed that these seven ring groups are made up of thousands of smaller rings. The exact number is not known. Continue the conversation on


What was the name of two space probes launched in 1977 which sent back remarkable pictures of Jupiter, Saturn, Uranus and Neptune?

Voyager - Planetary Voyage   Planet montage (left to right), Neptune, Uranus, Saturn, Jupiter The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. As originally designed, the Voyagers were to conduct closeup studies of Jupiter and Saturn, Saturn's rings, and the larger moons of the two planets. To accomplish their two-planet mission, the spacecraft were built to last five years. But as the mission went on, and with the successful achievement of all its objectives, the additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible -- and irresistible to mission scientists and engineers at the Voyagers' home at the Jet Propulsion Laboratory in Pasadena, California. As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left the Earth. Their two-planet mission became four. Their five-year lifetimes stretched to 12 and is now near thirty-seven years. Eventually, between them, Voyager 1 and 2 would explore all the giant outer planets of our solar system, 48 of their moons, and the unique systems of rings and magnetic fields those planets possess. Had the Voyager mission ended after the Jupiter and Saturn flybys alone, it still would have provided the material to rewrite astronomy textbooks. But having doubled their already ambitious itineraries, the Voyagers returned to Earth information over the years that has revolutionized the science of planetary astronomy, helping to resolve key questions while raising intriguing new ones about the origin and evolution of the planets in our solar system. History Of The Voyager Mission The Voyager mission was designed to take advantage of a rare geometric arrangement of the outer planets in the late 1970s and the 1980s which allowed for a four-planet tour for a minimum of propellant and trip time. This layout of Jupiter, Saturn, Uranus and Neptune, which occurs about every 175 years, allows a spacecraft on a particular flight path to swing from one planet to the next without the need for large onboard propulsion systems. The flyby of each planet bends the spacecraft's flight path and increases its velocity enough to deliver it to the next destination. Using this "gravity assist" technique, first demonstrated with NASA's Mariner 10 Venus/Mercury mission in 1973-74, the flight time to Neptune was reduced from 30 years to 12. While the four-planet mission was known to be possible, it was deemed to be too expensive to build a spacecraft that could go the distance, carry the instruments needed and last long enough to accomplish such a long mission. Thus, the Voyagers were funded to conduct intensive flyby studies of Jupiter and Saturn only. More than 10,000 trajectories were studied before choosing the two that would allow close flybys of Jupiter and its large moon Io, and Saturn and its large moon Titan; the chosen flight path for Voyager 2 also preserved the option to continue on to Uranus and Neptune. From the NASA Kennedy Space Center at Cape Canaveral, Florida, Voyager 2 was launched first, on August 20, 1977; Voyager 1 was launched on a faster, shorter trajectory on September 5, 1977. Both spacecraft were delivered to space aboard Titan-Centaur expendable rockets. The prime Voyager mission to Jupiter and Saturn brought Voyager 1 to Jupiter on March 5, 1979, and Saturn on November 12, 1980, followed by Voyager 2 to Jupiter on July 9, 1979, and Saturn on August 25, 1981. Voyager 1's trajectory, designed to send the spacecraft closely past the large moon Titan and behind Saturn's rings, bent the spacecraft's path inexorably northward out of the ecliptic plane -- the plane in which most of the planets orbit the Sun. Voyager 2 was aimed to fly by Saturn at a point that would automatically send the spacecraft in the direction of Uranus. After Voyager 2's successful Saturn encounter, it was shown that Voyager 2 would likely be able to fly on to Uranus with all instruments operat


Which planet has one moon called Charon?

How many moons does each planet have?  name of the moons | eNotes How many moons does each planet have?  name of the moons linda-allen | High School Teacher | (Level 3) Senior Educator Posted on January 10, 2010 at 10:19 PM Seems like this would be an easy question for you to find the answer yourself. In fact, if you had typed your question into the search box on the eNotes home page, you would have been directed to a page on eNotes titled "Space--How Many Moons Does Each Planet Have"? I have typed some of that info for you here. If you want to know the names we have given to each of the many moons, then click on the link in the Sources section and check out that page. Mercury--0 moons triteamdan | Teacher | (Level 2) Adjunct Educator Posted on February 18, 2012 at 9:18 AM No one knows.  New moons are discovered around the outer planets with fair regularity, the most recent of which was a fourth moon of Pluto's  Please note that there have also been new planets discovered recently (reclassified as dwarf planets) some of which also have moons. like 3 dislike 1 krishna-agrawala | College Teacher | (Level 3) Valedictorian Posted on Moons, also called satellites, are heavenly bodies that circle planets. IN our solar system seven of the planets have moon circling them. The names of these planets with number of moon that each of them have are listed below. Earth    ...   1.  This is called Moon Pluto     ...   1. This satellite is named Charon. Mars      ...   2. These are named Phobos and Deimos. Neptune ...   8. Only two of these can be seen by telescope on earth. These are named Titon and Nereid. Uranus   ...  15. Largest five of these are named Titania, Ariel, Miranda, Puck and Portia Jupiter   ...  16. Four of the largest of these are called Io, Europa, Ganymede ,and Callisto. Saturn   ...  18. Largest five of these are named Titan, Iapetus, Rhea, Dione and Tithys. There are no known satellites or moons of Mercury and Venus. like 5 dislike 1


What are the clouds of interstellar dust, said to be the birthplace of stars?

What is the interstellar medium? Links What is the Interstellar Medium? Simply put, the interstellar medium is the material which fills the space between the stars. Many people imagine outer space to be a complete vacuum, devoid of any material. Although the interstellar regions are more devoid of matter than any vacuum artificially created on earth, there is matter in space. These regions have very low densities and consist mainly of gas (99%) and dust . In total, approximately 15% of the visible matter in the Milky Way is composed of interstellar gas and dust. Interstellar Gas: Approximately 99% of the interstellar medium is composed of interstellar gas, and of its mass, about 75% is in the form of hydrogen (either molecular or atomic), with the remaining 25% as helium. The interstellar gas consists partly of neutral atoms and molecules , as well as charged particles, such as ions and electrons . This gas is extremely dilute, with an average density of about 1 atom per cubic centimeter. (For comparison, the air we breathe has a density of approximately 30,000,000,000,000,000,000 molecules per cubic centimeter.) Even though the interstellar gas is very dilute, the amount of matter adds up over the vast distances between the stars. The interstellar gas is typically found in two forms: Cold clouds of neutral atomic or molecular hydrogen; and Hot ionized hydrogen near hot young stars. The cold clouds of neutral or molecular hydrogen are the birthplace of new stars if they become gravitationally unstable and collapse. The neutral and molecular forms emit radiation in the radio band of the electromagnetic spectrum . The ionized hydrogen is produced when large amounts of ultraviolet radiation are released by hot newly-formed stars. This radiation ionizes the surrounding clouds of gas. Visible light is emitted when electrons recombine with the ionized hydrogen, which is seen as beautiful red colors of emission nebulae. Examples of emission nebulae are the Trifid Nebula or the Orion Nebula (seen in this photograph). Interstellar Dust: Interstellar dust is not like the dust that you might find under your bed; it is made of very different substances. These dust particles are extremely small, just a fraction of a micron across, which happens to be approximately the wavelength of blue light waves. The particles are irregularly shaped, and are composed of silicates, carbon, ice, and/or iron compounds. When light from other stars passes through the dust, a few things can happen. If the dust is thick enough, the light will be completely blocked, leading to dark areas. These dark clouds are known as dark nebulae. The Horsehead Nebula, seen to the left, is an example of this. Light passing through a dust cloud may not be completely blocked, although all wavelengths of light passing through will be dimmed somewhat. This phenomenon is known as extinction . The extinction is caused by the light being scattered off of the dust particles out of our line of sight, preventing the light from reaching us. The amount that the light is dimmed depends upon a few factors, including the thickness a nd density of the dust cloud, as well as the wavelength (color) of the light. Because of the size of the dust particles, scattering of blue light is favored. Therefore, less of the blue light reaches us, which means that the light that reaches us is more red than it would have been without the interstellar dust. This effect is known as interstellar reddening . (Note that this is not the same thing as redshift , which is due to the effects of relative movement between a light source and its receiver.) This process is similar to those that make the sun red at sunset. (To see an explanation of extinction and interstellar reddening that is more mathematical, please visit this site .) In turn, a dust cloud that is illuminated by star light, when viewed from the side, appears blue, as in the close-up of the "Egg Nebula" seen at right. This is similar to the blue sky we see, which is produced by sunlight scattered by the Earth's atmosphere. Aside from passing th


What is the astronomical unit equal to 32,616 light years?

Astronomical Unit Conversion - Measurement conversion A-I Measurement conversion A-I Most often used measurement conversion parsecs to kilometers (pc to km) converter 1 parsec is equal 30856776029497 kilometers (km) kilometers to parsecs (km to pc) converter 1 kilometer (km) is equal 3.2407792669074E-14 parsec kilometers to miles (km to mi) converter 1 kilometer (km) is equal 0.62118591342441 mile (mi) miles to kilometers (mi to km) converter 1 mile (mi) is equal 1.6098240130516 kilometers (km) miles to light-years (traditional) converter 1 mile (mi) is equal 1.7027507939076E-13 light-year (traditional) light-years (traditional) to miles converter 1 light-year (traditional) is equal 5872850000000 miles (mi) use this converter Definition Astronomical unit - a unit of length that is roughly equal to 150 million kilometers, the average distance from the Earth to the Sun. Other units of length used in astronomy are based on the speed of light and the time it takes light to cover a specific distance. Units of measurement parsec, astronomical unit (AU), kilometer (km), meter (m), mile (mi), light-year (Julian), light-year (Gregorian), light-year (traditional), light-year (tropical / solar), light-week, light-day, light-hour, light-minut, light-second About Astronomical Unit Conversion tool. We use rounding at unit-conversion.info. This means that some results will be rounded to avoid the numbers getting too long. While often rounding works up to a specific decimal place, we’ve decided that limiting the length of the result to 13 digits would be more favorable to keep the results consistent. The converters accept scientific notation and converts immediately.


Which is the second largest planet in the solar system?

What is the Second Biggest Planet in the Solar System? - Universe Today   Universe Today What is the Second Biggest Planet in the Solar System? Article Updated: 24 Dec , 2015 by Fraser Cain The biggest planet in the Solar System is Jupiter. But the title for the second biggest planet in our Solar System goes to Saturn. Just for a comparison, Jupiter measures 142,984 km across its equator. Saturn for comparison is only 120,536. So Jupiter is only 1.18 times as big of Saturn. Saturn is big, but it has a much lower mass. Once again, Jupiter is 3.34 times as massive as Saturn. Since Saturn is so big, but has so little mass, it has a very low density. In fact, if you had a pool big enough, Saturn would float. The density of Saturn is less than water. And this means that you wouldn’t experience a lot of gravity if you tried to walk on the “surface of Saturn”. If you were standing on the surface of Saturn (I know, that’s impossible), you would experience only 91% the force of Earth’s gravity. If you wanted to compare Saturn to Earth, it’s 9.4 times as big as the Earth, and 95 times as massive. It it was just a hollow shell, you could pack 763 Earths inside Saturn, with a little room to spare. Wanna see Jupiter? Here are amazing telescopes from Amazon.com which you can buy at reasonable prices: Here’s the article about how Jupiter is the biggest planet . And here’s another article about just how big planets can get . If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn , and another page on Saturn from NASA’s Solar System Exploration Guide . We have recorded a whole series of podcasts about the Solar System at Astronomy Cast . Check them out here.