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Quickie Questions - Other Solar System Stuff - Asteroids/Meteors/Meteroids/Comets

Date Answered Questioner (age, location) Question Answer

February 9, 2010Fernando (age 33, Quintana Roo/ Mexico) At what distance from the earth can an asteriods trayectory be affected by earth´s gravity and thus possibly impacting the earth? The answer is unique for each asteroid. The gravitational force is proportional to the product of the interacting masses (in this case our planet mass times the asteroid mass) and inversely proportional to the square of the distance between them. Also, keep in mind that even if our planet affects a asteroid orbit, it doesn't neccesarily mean that the asteroid will impact Earth.
February 5, 2010Angel (age 33, Washington, USA) I was watching a factually based movie called, Seven Years in Tibet. During the mid to late 1940's a comet like object was shown flying thru the sky. What was it? Could it be the Comet C/1947 X1 (Southern Comet)? It was independently discovered by many people in the Southern Hemisphere during December 7 and 8 of 1947 . There is also a comet that was seen mainly from Africa during the total solar eclipse of November 1, 1948 (it was just 2° from the sun).
January 15, 2010Olivia (age 9, WV/USA) How could measuring the orbit of a comet help scientists understand when it will next be visible from earth? Because comets, as planets, follow periodical orbits around the Sun. These orbitas are controled by KEPPLER'S LAWS. Use our Interactive Comet Animation to some things about how comets work.
January 12, 2010kyra (age 11, new york) why is halley's comet famous Halley comet was the first periodic comet identified. It is clearly visible to the naked eye every 75 to 76 years, and for this reason easily identified in the observations.
January 7, 2010Kaniha (age 14, New Jersey, USA) Dust tail tends to ____________ the comet's orbit so it doesn't always point away from the sun. What would the black be? Please help me! Thank you very much. The usually brighter dust tails are broad and diffuse and curve slightly, lagging behind the radial direction. I assume the word you are looking for is "follow".
January 7, 2010TILAAGAN (age 10, MALAYSIA) WHICH WEAPON DO A SCIENTIST USE TO DESTROY A ASTEROID None has been used yet, but this article discusses the option of sending a spacecraft to change the trajectory of an asteroid.
October 27, 2009GESIGASRI (age 10, MALAYSIA) WHAT IS A KUIPER BELT ? The outer edge of our Solar System is not empty. There are many, many huge spheres of ice and rock out near Pluto's orbit. Astronomers call this huge group of planetoids "Kuiper Belt Objects", or "KBOs" for short. The Kuiper Belt is a bit like the asteroid belt, but much farther from the Sun.
October 27, 2009A.GESIGASRI (age 10, MALAYSIA) WHAT IS A KUIPER BELT ? The outer edge of our Solar System is not empty. There are many, many huge spheres of ice and rock out near Pluto's orbit. Astronomers call this huge group of planetoids "Kuiper Belt Objects", or "KBOs" for short. The Kuiper Belt is a bit like the asteroid belt, but much farther from the Sun.
October 27, 2009rashel (age 10, united states) What causes the tail on Halley's Comet? When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long.
October 16, 2009Amanda (age 14, usa) What type of rock is inside a comet? The mission Deep Impact, a 820-pound spacecraft slammed into the comet Tempel 1 at 23,000 miles an hour, tossed up thousands of tons of ice and dust from the comet. The Spitzer Space Telescope detected specific colors of infrared light that indicated that Tempel 1 contained clays and carbonates, the minerals of limestone and seashells. The mistery for scientists now is that both require liquid water to form!
October 6, 2009Sarah (age 12, america) what is the most famous comet? The oldest and probably better knwon comet is the Halley Comet, it has been observed by astronomers since at least 240 BC. Halley's Comet last appeared in the inner Solar System in 1986, and will next appear in mid-2061.
September 17, 2009Caroline (age 12, South America) How far away is Earth to asteroid belt? The highest concentration of the asteroid belt lies at about 2.8 AU from the Sun, or 1.8 AU (about 270 million km) from Earth.
August 13, 2009niquea (age 13, washington dc) what moves around the sun and has a long tail? Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long.
August 12, 2009monica (age 11, indiana,U.S.A.) Why do asteriods orbit the sun? Why/how do they stay in the Asteroid belt? Asteroids were formed, as the Sun, planets, etc., from the solar nebula. As the planets do (and the asteroids are supposed to be the the remains of an early planet, which broke up early in the solar system), the rotate around the Sun as a produt of the rotational motion of the solar nebula.
August 6, 2009melody (age 11, new mexico) how many comets a year travel into the solar system and circle the sun? I don't think there is a final answer to your question. For example, the so-called long-period comets were long thought to come from the outer region of the Oort Cloud, a remnant of the nebula from which the solar system formed some. It is thought to contain billions of comets, most of which are far too small and distant to be seen even with powerful telescopes.
July 29, 2009aMANDEEP (age 11, ENGLAAND) At what time will there be a shooting star at may2 What are know as "shooting stars" are not stars, they are caused by tiny bits of dust and rock called meteoroids falling into the Earth's atmosphere and burning up. They are so tiny that it is not possible to keep track of them, so they are no predicted.
July 28, 2009nooshin (age 21, iran) how can we find the exact orbit of comets? I think this NASA website is he correct place to find the information you are looking for.
July 22, 2009sofia (age 15, portal,ga) what is the kuiper belt? The outer edge of our Solar System is not empty. There are many, many huge spheres of ice and rock out near Pluto's orbit. Astronomers call this huge group of planetoids "Kuiper Belt Objects", or "KBOs" for short. The Kuiper Belt is a bit like the asteroid belt, but much farther from the Sun. More information on our web page The Kuiper Belt.
June 17, 2009Tenzin (age 12, West Bengal, India) Why can comets be seen after so long times ? Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches, and that some comets make repeated trips. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. More information on our web site Comets.
April 20, 2009Kelli (age 11, Philippines) Is it true that comets tell about following disasters? Although it was a widely held believe in ancient times, we now know that comets are celestial objets orbiting around the sun. They don't predict disasters.
March 23, 2009Quincey (age 15, Kansas) During which phase did meteorites form? It is believed that meteorites are remanents of the very early phases of the formation of the solar system from the solar nebula.
March 11, 2009Gabriel (age 14, philippines) does a comet die? A comet could atracted by the Sun or any other celestial body and hit their surface and destroy. A recent example was the comet Shoemaker-Levy 9 collision with Jupiter.
March 5, 2009DJ (age 20, alabama) is there a comet comin in the next 2months This useful web page: Visual Comets in the Future (Northern Hemisphere) offers information on all visible comets up to 2013.
February 25, 2009pam (age 35, MS/ USA) When did 'Asteroid Hermes' come close to earth? Hermes was first observed in 1937 as a fast-moving bright object 460,000 miles from Earth. It then disappeared from view, making an unobserved swing past Earth in 1942 at a distance of 378,000 miles -- which, in astronomical terms, is quite close, about 1.6 times the distance between Earth and the moon. Much more information here.
February 18, 2009Danielle (age 9, USA; Georgia) Why does Halley's Comet travel through our solar system regularly? As many other comets, Halley's is controlled by the gravitational field of the Sun. Halley's comet returns close to the Sun every 76 years or so. It is considered a short period comet.
February 8, 2009Annie (age 31, canada) I want to know if a comet named Atemone exist for real? I couldn't find any information about this comet!
February 2, 2009Benjamin(again) (age 10(again), Malaysia(again)) Can you imagine that what happens if a comet gets too close to the sun that is many time closet than mercury(or be about a few metre away)?And do you know that Barack Obama will be the 44th president of the united states in 20/1/2009? Comets that get close to the Sun can suffer a good deal of transformation. A considerable part of its nucleus can dissapear, the nucleus can be broken, or the comet can just fall in to the Sun.
February 2, 2009john (age 12, califronia) how does comets form Your questions, and more, are answered in our web page Comets.
January 21, 2009Alex (age 12, Michigan, US) How often can comet Hale-bopp and Kohoutek be seen on Earth. When Hale-Bopp comet the comet passed within 0.77 AU of Jupiter in April 1996, its orbit was shortened considerablydue to the planet gravity, to a period of roughly 2 533 years. Comet Kohoutek is another long-period comet, with a period of about 75 000 years.
November 5, 2008Briana (age 10, United States) What are some interesting facts about Comet Wild 2? Comet Wild 2 is named after the scientist who discovered it. Paul Wild is an astronomer from Switzerland who discovered the comet in January 1978. Wild 2 is pronounced "Vilt 2". It takes this comet a little more than six years to go around the Sun once. Its orbit is shaped more like an oval, which astronomers call an ellipse, and it brings the comet a bit closer to the Sun than the planet Mars. The orbit also swings the comet out beyond the orbit of Jupiter. You can find more information on our web page Comet Wild 2<\>.
November 3, 2008Kayla (age 10, NJ Bloomfield) What year will Halley's Comet return? Comet Halley will return to the inner solar system in the year 2061, with a perihelion passage in early 2062.
September 16, 2008Troy (age 13, Florida, USA) If a comet or asteriod does hit us what will happen? Can we prepare for the collision? When is the next estimated year that a comet or asteriod will collide with Earth? Thank you. Note: You do not have to answer all the questions. Thank you. As far as scientists know, none of the known asteroids or comets is on a collision course with Earth. However, there surely are other that we still don't know. The degree of destruction can be estimated knowing the mass, speed and trayectory (impact point) of the comet.
September 15, 2008Jose (age 18, Guatemala) what is the excat orbit of Halley? Halley's orbit is retrograde, inclined 18 degrees to the ecliptic, and very eccentric. A very precise determination of its orbits is a serious scientific task (see this article.)
September 12, 2008jhustine (age 13, philippines) how asteroids being formed? Asteroids are small bodies that are believed to be left over from the beginning of the solar system 4.6 billion years ago. They are rocky objects with round or irregular shapes up to several hundred km across, but most are much smaller. More than 100,000 asteroids lie in a belt between Mars and Jupiter. These asteroids lie in a location in the solar system where there seems to be a jump in the spacing between the planets. Scientists think that this debris may be the remains of an early planet, which broke up early in the solar system. Several thousand of the largest asteroids in this belt have been given names.
September 10, 2008Mike (age , ) Comet Halley will return to the inner solar system in the year 2061, with a perihelion passage in early 2062. This coould explain the difference between the dates mentioned. I think the question asked left room for both answers.
September 10, 2008Mike (age , ) Comet Halley will return to the inner solar system in the year 2061, with a perihelion passage in early 2062. This coould explain the difference between the dates mentioned.
August 20, 2008Gaige (age 13, Illionois) In the year 2019 the astriod were would it most likely hit earth. I assume you are talking about Apophis, the near-Earth asteroid that was initially thought to have a relatively large probability (up to 2.7%) of striking Earth in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029.
August 19, 2008Lauren (age 15, Pennsylvania) How big is Halley's comet in diameter? Although its coma may extend about 100 million kilometres into space, Halley's nucleus is relatively small, approximately 16x8x8 kilometers. More information here.
August 19, 2008Ava (age 11, New hamshire) um.... could you talk about the asteroid Apophis? I would like to know more about it. Apophis is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a relatively large probability (up to 2.7%) that it would strike the Earth in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. MOre information here.
August 14, 2008lakiesha holder (age 12, kentucky) when will a comet destroy the earth?and will i be around when it happens As far as scientists know, none of the known asteroids or comets is on a collision course with Earth. However, there surely are other that we still don't know.
June 24, 2008Hailey (age 11, OR,USA) Who was the first person to observe Halley's Comet? Halley's comet is named after Edmond G. Halley who was the first to suggest that comets were natural phenomena of the solar system, in orbit around the Sun. He suggested that a certain comet was a regular visitor, returning every 76 years, and was, in fact, the same one which had been observed since 240 BC, but in particular in the years 1531, 1607, and 1682, dates which for him were recent history. In 1682 he predicted the comet would return again in 1758, and sure enough, the comet arrived in March 1759. Halley's comet made a particularly bright appearance in 1910. It also was recorded in a famous ancient tapestry after its 1066 appearance. More information on our web page Halley's Comet.
June 17, 2008kiara (age 13, indiana) when was the last time a asteroid came to earth? The latest known impact happened in 1908, when an asteroid exploded above Tunguska, Siberia, blowing down trees across 2,000 square kilometers. Because the asteroid exploded in the atmosphere, there's no crater.
June 17, 2008kiara jackson (age 13, gary,indiana) when was the last time a asteroid came to earth? The latest known impact happened in 1908, when an asteroid exploded above Tunguska, Siberia, blowing down trees across 2,000 square kilometers. Because the asteroid exploded in the atmosphere, there's no crater.
June 17, 2008BRIANNA (age 11, CANADA) ASTRONOMERS THINK THAT MOST COMETS COME FROM THIS CLUSTER.NAME IT. Short-period comets come from the Kuiper Belt (a region of comets in orbit beyond Neptune). Long-period comets are originated from the Oort cloud in the outermost limits of our solar system.
April 21, 2008Patricia (age 20, UK) Why are some comets hyperbolic and parabolic, whereas other are elliptic, meaning they repeat their journey and come back towards the sun? thank you Short-period comets are thought to originate in the Kuiper belt, while long-period comets are from the more distant Oort cloud. Occasionally the gravitational influence of the outer planets or nearby stars may throw one of these bodies into an elliptical orbit.
April 8, 2008chacha (age 16, Canada) Why are people interested in comets? There are many reasons to study comets. Comets may be some of the oldest, basically unchanged objects in the solar system. The study of their composition could offer information about the composition of solar nebula. There is also the possibility that coments have played a role in the progress of life, maybe even in the extinction of dinosaurs.
April 7, 2008Juleia (age 15, Kentucky) who and when discovered the astroid belt?? The discovery of the asteroid belt is a good example of how science frequently interconnects different epochs. Here is a nice description of the successive events that ended with the discovery of the belt.
April 3, 2008Gaige (age 13, Illinois) If we have stars fall down to Earth then how come the famous stars like Orion dont? What we see as "shooting stars" are really meteors. Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called "shooting stars" or "falling stars", though they are not stars at all. Meteors are caused by the entry of small pieces of rock, dust, or metal from space into the atmosphere at extremely high speeds.
March 19, 2008RUBEN (age 11, singapore) How are asteroid fromed Asteroids are small bodies that are believed to be left over from the beginning of the solar system 4.6 billion years ago. More than 100 000 asteroids lie in a belt between Mars and Jupiter. These asteroids lie in a location in the solar system where there seems to be a jump in the spacing between the planets. Scientists think that this debris may be the remains of an early planet, which broke up early in the solar system.
March 17, 2008neshia (age 14, WH/FL.) in the solar system how do comets form and do they ever meet?and how if they do? Your questions, and more, are answered in our web page Comets.
February 8, 2008Sharon (age 24, South Africa) I would love to know whether scientists speculate that a major comet could in our life time, be headed to earth and cause a major catastrophe?
And is there any hope for people to survive, if its more or less the same size that hit which ended the dinosaur era, given the latest technology at hand?
Kind Regards
Sharon
As far as scientists know, none of the known asteroids or comets is on a collision course with Earth. However, there surely are other that we still don't know.
January 24, 2008Anudip (age 17, India) What is cormet means and how they form? Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long. Much more information in our web page Comets.
January 4, 2008Aliecia (age 10, Minnesota) What is the biggest meteoroid that has hit Earth? The biggest asteroid to hit the Earth in the last few centuries was in Siberia on June 30, 1908. The rock has been calculated to be about 100 000 tons and the size of a large house.
January 2, 2008sambit (age 13, orissa/india) why should we research on comets? A comet originates from a cloud of debris remaining from the condensation of the solar nebula. Comets are unique because they are created in the outer solar system, and are greatly affected by the planets they pass. The study of comets offers an inside on far away zones of our system.
December 26, 2007Daniel (age 10, canada) what is the difference between asteroids and meteors? Asteroids are thousands of small rocky bodies that orbit the Sun in a belt between Mars and Jupiter. They can be as small as 1 kilometer(km) across or as large as 700 km. Meteors are space particles that have been left behind by comets or broken off from asteroids. When a meteor penetrates an atmosphere is heated because the friction with the gas, and leaves a bright trail of light across the sky.
September 19, 2007indi (age 10, australia) where is haleys comet going to appear next? Comet is a periodic comet that can be seen every 75–76 years. Last perihelion happened on February 9, 1986, the next one is predicted to be around July 28, 2061.
September 19, 2007taylor (age 13, new york) If a comet was to hit a planet and change it's orbit to crossing the Earth's, what are the chances of it hitting Earth? The answer to your question would be too extense for this section, but I think you will find a good discussion on this topic in this article.
September 12, 2007karen Because the amount of questions we receive it was impossible for me to answer your question in time to observe the Perseids meteor shower this year (it happened Sunday, August 12th.) However, because the source of the shower is the tail of the Comet Swift-Tuttle, which we glide through every year in August, you will be able to see this beautiful phenomenon next year again. For next year shower date, check the website of the International Meteor Organization.
September 12, 2007brad (age 10, michigan, america) how could dwarf planet ceres contain its spherical shape if it is always hit by asteroids? Ceres, the first asteroid to be discovered, is by far the largest and most massive asteroid in the main asteroid belt. In fact, it comprises about a third of the total mass of the entire main belt. Its size and mass are sufficient to give it a spherical shape, like the planets. However, it is still much smaller than any of the planets, similar in size to Saturn’s medium-sized moons Tethys and Dione. Recent observations by the Hubble Space Telescope suggest that Ceres is a very interesting body, worthy of a dedicated mission to visit it. For example, like the planets and large moons, Ceres has "differentiated," meaning that its interior is separated into crust, mantle, and core layers, with the densest materials being at the center. Extracted from The Planetary Society.
August 17, 2007josh (age 18, usa) Describe what the surface of a comet looks like? The surface of the nucleus of a comet is as light weight and full of holes as a sponge. The holes of this "sponge" are filled with ices like water, carbon dioxide, and carbon monoxide.
August 17, 2007josh (age 18, usa) what is the nucleus of a comet? The nucleus of a comet is the central portion of the head of a comet. It is a solid part of the comet, made of a special sort of dust which is called "fluffy" because it could be as light weight and full of holes as a sponge. The holes of this "sponge" are filled with ices like water, carbon dioxide (dry ice), and carbon monoxide (what comes out of your car). More information in our web page The Cometa Nucleus.
August 17, 2007jacinda (age 13, cape town) what is the nucleus of a comet? The nucleus of a comet is the central portion of the head of a comet. It is a solid part of the comet, made of a special sort of dust which is called "fluffy" because it could be as light weight and full of holes as a sponge. The holes of this "sponge" are filled with ices like water, carbon dioxide (dry ice), and carbon monoxide (what comes out of your car). More information in our web page The Cometa Nucleus.
July 25, 2007Rachelle (age 27, NC USA) isn't there a massive asteroid/comet already on its way to annialate earth within the next 20yrs
and yet it will not cause extinction?
On July 2002, a 1.2-mile-wide asteroid was detected. It has an orbit around our sun of 837 days, and early calculations indicated a small chance that this asteroid will collide with Earth on February 2019. Astronomers from NASA and around the world are monitoring the asteroid known as 2002 NT7, but say that the calculations are very preliminary and the actual chance of it striking our planet are minimal, it may not be on an actual collision course. This article offers more details.
July 18, 2007Danielle (age 11, New Zealand) Does Halley's comet have a colour? if so what colour is it? Go to our web page Halley's Comet and decide by yourself (and, at the same time, learn more about this comet).
July 17, 2007Isabell (age 11, Canada) How far is Ceres from the sun Ceres is at a mean distance of 413 900 000 km from the Sun.
July 10, 2007 (age 14, ohio) Meteorites ate thought to have formed within our solar system during the what phase During the formation of our system!
July 10, 2007 how old are the oldest known meteorites The oldest meteorite specimens are remnants of the very first geologic processes to occur in our solar system 4.6 billion years ago. This webpage offers an extensive discussion of this topic.
July 3, 2007sunitha (age 31, india) how do scientists predict meteor hits?my daughter likes to know.i searched the net i did not find a good answer for my 7-year-old The simplest answer for a kid that age is that once an asteroid has been identified, scientists calculate its orbit, and the possibility of a collision with our planet, or any other planet, as it was successfully predicted with the comet Shoemaker-Levy collision with Jupiter (go to this NASA webpage for wonderful pictures).
July 3, 2007Crystal (age 19, california) What is the minerals name of where an astrode hits? Tektites, from Greek tektos, molten, are natural glass objects, which according to most scientists have been formed by the impact of large meteorites on Earth's surface.
July 2, 2007Mario (age 8, Saskatchewan, Canada) Is the astroid belt a planet that exploded? Asteroids are primoridal objects left over from the formation of the Solar System. While some have suggested that they are the remains of a protoplanet that was destroyed in a massive collision long ago, the prevailing view is that asteroids are leftover rocky matter that never successfully coalesced into a planet. Extracted from Main Asteroid Belt.
May 23, 2007Logan (age 9, Pennsylvania/USA) WHEN WAS THE LAST TIME THAT HALLEY'S COMET PASSED OVER THE UNITED STATES? The last time Halley's Comet visited the inner Solar System was 1986. The next visit will be in mid 2061.
May 11, 2007katie (age 10, mn\us) why are there astrods The term asteroid is generally used to indicate a diverse group of small celestial bodies that drift in the solar system in an orbit between the orbits of Mars and Jupiter. It is thought that these asteroids are remnants of the protoplanetary disc, in an orbit where a planet was not formed.
May 10, 2007Rala (sc,usa) What is the differance between a Meteor and a Meteorid? A meteorite is a relatively small extra-terrestrial body that reaches the Earth's surface. While in space these bodies are called meteoroids and are called meteors after entering Earth's atmosphere, but before reaching the surface. These are "small" asteroids, approximately boulder-sized or less. Upon entering the atmosphere, air drag and friction cause the body to heat up and emit light, thus forming a fireball or shooting star. More information on our web page Meteors. Definition from Meteorites.
March 21, 2007Ruthie (age 13, Colorado/United States) How large are Comets normally? Comets vary in size, but, for example, the nucleus of Comet Halley is approximately 16x8x8 kilometers.
March 21, 2007danielle (age 11, new yorl) when is the size of the comets tail the shortest When it is far from the Sun!
March 20, 2007rosario (age 13, colorado) why are comets a fuzzy star that is in space all the time? and why cant we see them from here? Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches. Some comets make repeated trips. When comets get close enough to the Sun, heat makes them start to evaporate, creating jets of gas and dust form long tails that we can see from Earth. More information (and pictures!) can be found in our web page Comets.
March 5, 2007april (age 12, perth) what are astroides made of? There are two main theories of the asteroids formation. The most widely accepted is that asteroids are leftover rocky matter that never successfully coalesced into a planet. Other have suggested that they are the remains of a protoplanet that was destroyed in a massive collision. In any case, the asteroids are objects left from the formation of the Solar System. The asteroids have been clasified bi its composition: A type: Contain an abundant amount of olivine. C type: This asteroids appear to be similar to the carbonaceous meteorites and are believed to be the most primitive materials in the solar system. D type: Redder in color than the P type asteroids. E type: High concentration of enstatite. M type: Contain an iron-nickel alloy. P type: Reddish and are currently unknown in composition. S type: Appear to contain silicate minerals pyroxene and olivine as well as considerable amount of metals.
February 24, 2007tyler (age 9, mi) when is halleys coment due to pass bay city? The next pass of Comet Halley near the Sun will be at or around 2061.
February 13, 2007JENNY (age 11, PHILIPPINES) NAME THE SEVEN KINDS OF ASTEROIDS. There are three basic types of asteroids: C: carbonaceous, silicate materials and carbon compounds. S: silicate materials without carbon compounds. M: metals like iron and nickel. New clasifications include more details. The Tholen classification describes 14 types, and the SMASS classification includes up to 24 types. These clasifications are described at Wikipedia/Asteroid Spectral Types.
February 12, 2007sophie (age 15) what is the differenc between an orbit of a planet and the orbit of a comet In mathematics, eccentricity is a measure of how much the orbit deviates from being circular. In particular, the eccentricity of a circle is zero, and the eccentricity of a (non-circle) ellipse is between 0 and 1. Now, although the orbits of the planets are not exactly circular, they are very close. For example, the eccentricity of our planet orbit is 0.017, meaning an orbit very close to a circular shape. Comets, however, have very large eccentricities, often approaching one. This topic would be easier to understand if you play with our Interactive Comet Animation.
February 12, 2007sophie (age 15) what is the differenc between an orbit of a planet and the orbit of a comet In mathematics, eccentricity is a measure of how much the orbit deviates from being circular. In particular, the eccentricity of a circle is zero, and the eccentricity of a (non-circle) ellipse is between 0 and 1. Now, although the orbits of the planets are not exactly circular, they are very close. For example, the eccentricity of our planet orbit is 0.017, meaning an orbit very close to a circular shape. Comets, however, have very large eccentricities, often approaching one. This topic would be easier to understand if you play with our Interactive Comet Animation.
February 6, 2007ugonna (age 12, toronto) are comets tail poisinous Comets are lumps of ice and dust that periodically come into the center of the solar system. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long. For more information, please visit our web page Comets.
February 5, 2007Kathleen (age 45, Canada) how wide in miles is the asteroid belt between Mars & Jupiter? The asteroid belt falls roughly between Mars and Jupiter. The main section lies between 2.06 and 3.27 AU (1 AU = 149 597 871 km or 92,955,807 miles).
January 30, 2007lesedi (age 18, south africa) why comet appear? Comets are small bodies of the solar system that orbit the Sun. They are classified according to their orbital periods: Short-period comets or periodic comets, have orbits of less than 200 years, while long-period comets have longer orbits but remain gravitationally bound to the Sun.
January 30, 2007Lucy (age 12, Switzerland) Is comet hyakutake a new type of comet? Comets are classified according to their orbital periods: Short-period comets or periodic comets, have orbits of less than 200 years, while long-period comets have longer orbits but remain gravitationally bound to the Sun. The comet Hyakutake also designated as Comet C/1996 B2, is a long period comet.
January 30, 2007Erika (age 12, North Carolina) What are the three largest asteroids???? Thank you sooo much for answering my question, I really appreciate it!!!!!!!! The three largest asteroids are Ceres, Pallas, and Vesta, . Their masses are: Ceres = (4.35 ± 0.05) × 10^-10 MSun, Pallas = (1.60 ± 0.04) × 10^-10 MSun, Vesta = (1.52 ± 0.09) × 10^-10 MSun.
January 30, 2007Erika (age 12, North Carolina) How do asteroids form??? There are two main theories of the asteroids formation. The most widely accepted is that asteroids are leftover rocky matter that never successfully coalesced into a planet. Other have suggested that they are the remains of a protoplanet that was destroyed in a massive collision. In any case, the asteroids are objects left from the formation of the Solar System.
January 25, 2007Howdy (age 11, New Hampshire) How long is the asteroid belt? Please get this information to me ASAP The asteroid belt falls roughly between Mars and Jupiter. The main section lies between 2.06 and 3.27 AU (1 AU = 149 597 871 km or 92,955,807 miles).
January 10, 2007Joana (age 20, Singapore) What is the difference between a dawf planet and a planet? The International Astronomical Union (IAU) redefined "planet" in the Solar System by: (1) A planet is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and - has cleared the neighborhood around its orbit. A new definition was also established by the IAU: (2) A "dwarf planet" is a celestial body that - is in orbit around the Sun, - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, - has not cleared the neighborhood around its orbit, and - is not a satellite.
January 3, 2007Hayley (age 11, Indiana,USA) Where do comets come from? The origin of comets is still a topic in discussion. Some time ago they were thought to have originated outside the solar system; but modern theories suggest they were formed during the formation of the solar system.
December 9, 2006essence hicks (age 12, CT) what are comets. Comets are lumps of ice and dust that periodically come into the center of the solar system from somewhere in its outer reaches, and that some comets make repeated trips. When comets get close enough to the Sun, heat makes them start to evaporate. Jets of gas and dust form long tails that we can see from Earth. These tails can sometimes be millions of miles long. For more information, visit our web page Comets.
December 9, 2006Brianna (age 13, new hampshire) what is the srtucture of a comet? A comet typically consists of a nucleus, coma, and tail. The nucleus is embedded in the coma and they together form the head of a comet. The tail of a comet can be very long and bright, and is the most distinctive feature of a comet. More about comets at our web page Comets.
December 6, 2006Zyra (age 19, Philippines) why meteors are more often seen late at night and usually numerous before dawn? In general, since comets are brightest when near the Sun, they are usually visible only at sunrise or sunset.
December 6, 2006Zyra (age 19, Philippines) why are comets more clearly visible when they approach the sun? As comets approach the Sun, heat makes them start to evaporate, and we can see from Earth the enormous tails of luminous material that extend for millions of kilometers from the head, away from the Sun.
December 1, 2006Kat (age 11, ) What are comets? Comets are lumps of ice and dust that come flying into the solar system from deep space. More information is available in our page Comets
March 12, 2003 John (high school) How do we know that comets are made mostly of ice? If comets were ice, how could they possibly make hundreds, if not thousands of trips through the solar system?

Good question! A good scientist always looks for the evidence to understand what’s going on. There have been several projects that have studied comets and have found evidence that comet nuclei are made mostly of ice. The Giotto spacecraft visited Halley’s comet taking pictures of its icy nucleus. More recently, studies using the Hubble Space Telescope and the International Ultraviolet Explorer found several types of ice in the nucleus of comet Hale-Bopp. Hopefully, the upcoming Rosetta mission will shed more light on the composition of comet nuclei when it lands on a comet in a few years.

Ice is actually a pretty strong substance and can travel without melting because it is very cold in most parts of the solar system. However, if a comet travels too close to the Sun, the ice melts!

February 24, 2003 Frankie(age 43, California, USA) What is the difference between comets, meteoroids, and asteroids? Four billion years ago when the solar system formed, asteroids were produced out of rock in the warm inner solar system and comets, made of ice and rock fragments, formed in the cold outer solar system. Meteoroids are smaller fragments of rock broken off of asteroids or dust released from a comet’s tail.
August 30, 2002 Dan (age 34, Minnesota, USA)
Erin
Some coworkers were talking today about a meteor or a comet that is heading towards Earth and should be here 2019, have you all heard of this? Initial calculations did predict the collision of the 1.2-mile wide asteroid with Earth in 2019, but more accurate calculations found that the asteroid will not hit Earth. I guess it can be very important to do math problems accurately!

August 5, 2002 Brian (age 37, Oregon, USA) What is the biggest crater from an asteroid in the USA? in the world? The biggest crater in the United States is at the mouth of Chesapeake Bay off the East coast. This recently-discovered underwater crater is 56 miles wide and formed 35 million years ago. The biggest crater in the world is called Chicxulub crater in the Gulf of Mexico. This crater is 112 miles wide and formed 65 million years ago. This impact was so large that it caused fires, tidal waves and earthquakes near the impact site and probably also changed the global climate. This impact occurred right when the dinosaurs and other animals went extinct and the extinction was probably related to the changes brought on by the impact.

July 15, 2002 Julie (age 38, Louisiana, USA) Would it be possible for researchers to bring a smaller comet to Earth to analyze? Funny you should ask! NASA is currently taking a close look at comets with their CONTOUR mission that launched July 3, 2002. They will be able to analyze what the comet nucleus is made of as they fly by.

April 11, 2002 Sarah (age 23, California, USA) Where can I buy a meteorite? I would suggest the Meteorite Exchange. That page lists several places to buy meteorites and has information about meteorites too. Prices vary a lot though -- from $10 for meteorite fragments to over $7,000 for an Ivory Coast specimen! Happy shopping!
December 19, 2001 Casey (middleschooler) Is there a thing called large comets because I can't find anything on them?? There is such a thing as small comets. So in contrast to small comets, other comets like Halley's Comet or Comet Linear would be large comets.
May 18, 2001 Jose (13, California, USA) Where is the asteroid belt located? And show me some pictures... More than 100,000 asteroids lie in a belt between Mars and Jupiter! Here is a page with images of asteroids.
April 24, 2001 Andrew (14, North Carolina, USA) I was wondering when will Halley's comet will come by again, and if I'm going to see it. Halley's comet is next scheduled to return in 2062. So, I bet you'll be around to see it!
January 29, 2001 Suzann (age 14, Tennessee, USA) What is the name of the spacecraft that is to encounter a comet in the near future? You know, there are actually a lot of comet mission fly-bys, close encounters or actual landings scheduled in the near future. This seems to be a hot area right now! So, please take a look at our new comet missions page...
October 9, 2000 Sammy (age 16, Michigan, USA) What is your theory on how the dinosaurs became extinct? The most popular theory is that a large comet or meteor crashed into the Earth. This changed the climate so much, that the dinosaurs couldn't survive.
October 15, 2000 Sarah (age 15, New York, USA) How many asteroids are there between Mars and Jupiter? Also what are there names? Have they been named yet? More than 100,000 asteroids lie in a belt between Mars and Jupiter. Scientists have tracked (determined the exact location) about 45% of these asteroids. Those are named. Some of those can be seen in our table of asteroids. Others are being tracked by a task group formed to track NEOs or Near Earth Objects.
September 29, 2000 Jess (age 14, New Zealand) What is an Oort Cloud and what does it do? Comets are said to come from the Oort cloud.
July 12, 2000 Carolyn (Virginia, USA ) What is a tektite? A tektite is a rounded, flat and glassy meteorite. It would be very small, with a size up to 4 inches.
May 15, 2000 Price (age 17, Australia) Why do newspapers show a parabola for the path of halley's comet, when we know it returns every 76 years Comet Halley actually follows an elliptical path. However, the path is so large, that newspapers probably don't feel the need to show the half not near the Sun.
May 8, 2000 Alexander (age 6, United Kingdom) How do comets get their energy to move through space?

Comets start in the Oort Cloud or the Kuiper Belt. It all begins when something forces the comet into motion. If two comets collide, for example, then one or both is sent tumbling out into space.

At some point, the comet may be captured by an object's gravity. Comets that we see, such as Halley's Comet, are caught in the Sun's gravity. So much like a planet, these comets orbit the star.

Other comets just pass on through. They pick up speed thanks to the Sun's gravity. This same technique is used by scientists when sending out probes. They use another planet's gravity to "throw" the probe towards its target.

February 15, 2000 Christina (age 17, Pennsylvania, USA) On this show one time they did a special on comets. They made a comet out of orrdinary household products and showed what the tail and the rest of the comet was made of. My question is do you know how to make this? Here is one place that tells how to make a model comet.
June 9 , 1999 Jenny (age 17, England) If meteors are about the size of a grain of sand then how come they look so bright? Is the air burning as well as the meteor? Also, why do some meteors leave a trail behind? Good questions; you're right, meteors do seem to glow very brightly for their small size. The speed that they enter the Earth's atmosphere (often faster than 26 miles per second) causes them to heat to tremendous temperatures. They don't even begin to vaporize until they reach about 1100 degrees C. The glow comes from the meteor vaporizing and heating gases in the atmosphere (so the atmosphere and meteor just heat up, but don't burn). It doesn't take much at such high temperatures to glow brightly. All meteors have a tail because the gases left behind remain heated for a while after the meteor passes. The size of the tail depends on the size and speed of the meteor.
May 12, 1999 Torie (age 11, New Jersey,USA) Do you know when the next comet is going to hit earth? We really don't know when, if ever, the next comet will hit earth. One theory suggests the first comet collided with Earth millions of years ago caused the dinosaurs to be come extinct. The good news is, scientists say a comet colliding into a planet in our solar system happens only once a millennium! Whew...
May 6, 1999 Jamie (age 16, Florida, USA) How often do comets appear? The time it takes for a comet to appear depends on its orbit. For example, Halley's comet appears every 76 years. See our page on comets for more information.
November 21, 1998 David (age 14, Colorado, USA) I have 2 questions about the asteroid 1997XF11. They are: 'Is there a relationship between the mass/size of an asteroid and the diameter of the crater created?'. Also, 'What is the difference if an asteroid hits the ocean rather than just hit on the land?' Size does matter: the larger the asteroid, the larger the crater. However, velocity also matters: the faster the asteroid, the larger the crater. An asteroid the size of 1997 XF11 colliding with the Earth at more than 17,000 miles an hour would explode with a force equal to almost 2 million Hiroshima-sized atomic bombs. If an asteroid like this hit land, it would instantly dig a crater 20 miles across and cloud the sky with so much dust and vapor that the sun would be darkened for weeks, if not months. If it were to fall in the ocean, it would create a tidal wave hundreds of feet high, causing extreme flooding for thousands of miles of coast line.
June 24, 1998 Julian (Age 25, Victoria, Australia) The film 'deep impact' depicts a spacecraft landing on the surface of a comet about the size of New York. Would it be possible for a craft to catch a comet like this and land on it? NASA is planning on doing just this! The Deep Space 4 mission will leave Earth in 2003, rendevous with a comet in 2005, scoop out some cometary material, and return to Earth in 2010. Check it out!
June 22, 1998 Atif (Age 26, Maryland, USA) In the movie Deep Impact they didn't tell the public where the comet would hit the earth until the day before it happened ... wouldn't we be able to predict the exact location plus or minus a 10 or 20 miles way in advance of the actual event .. let's say 6 months or a year? I haven't had a chance yet to see the movie, but I'd have to say you're right! It is approximated that NASA spends $3 million a year identifying and tracking any objects that may be approaching the Earth (estimate from ABC News). So I would hope that they would be able to tell where and when a comet was headed for Earth (with much more notice than just a day!).
May 12, 1998 Antonio (age 15, Florida, U.S.A.) What are comets composed of and where exactly do they form? We have a whole section just on comets--check it out!
April 21, 1998 Mr. Warren's 6th hour extension (age 12-13, Michigan, U.S.A.) What was the first recorded comet ever? Halley's comet was the first comet to be recognized as such. It is probably the same one which has been observed since 240 BC!
February 26, 1998 Adam (age 12, Colorado, USA) What would be the maximum size of an asteroid that a person could stand on and throw a baseball into orbit? Assuming a 90 mph fastball, the asteroid could have about a 100 km radius...but you would have to be able to throw really really fast!
February 11, 1998 Alfredo (age 11,Venezuela) I would like to know all about shooting stars. Shooting stars, or meteors, are caused when a meteoroid enters the atmosphere. (When the meteroid enters the atmosphere, it becomes a meteor.) Because of the friction caused by the Earth's atmosphere, the meteor burns up, causing the flash of light we see as a shooting star. These meteoroids are lumps of rock that are orbiting the Sun just like the Earth is. Meteor showers occur when the Earth passes through a group of meteoroids. These showers of shooting stars can be a great light show!
December 30, 1997 Emma and Suzi (age 11, Michigan, USA) How did comet Hale-Bopp form? Comets such as Hale-Bopp are made of ice and dust, left over from the beginning of our solar system. These chunks of ice and dust form the Oort cloud, outside the orbit o f Pluto. Sometimes the pull from a star changes the orbit of the chunks, sending them near the sun. They begin to evaporate, and pieces of gas and dust fall off and form the tail.
December 8, 1997 Morning Sun (age 11, Iowa, USA) What is the difference between an asteroid and a meteorite? An "asteroid" is considered to be any rocky or metallic body orbiting the Sun that does not have the characteristics of a comet. Asteroids are smaller than planets (from a few hundred feet to a few hundred miles across) and are usually, but not alway s, found in the "Asteroid Belt" between Mars and Jupiter. "Meteoroids" are smaller than asteroids and orbit the Sun near the Earth's orbit. Meteoroids often come from asteroids that have broken up into smaller pieces. "Meteorites" are simply meteoroids that have fallen to the Earth's surface from outer space. Most meteoroids don't survive to be meteorites because they burn up as they pass through the Earth's upper atmosphere.


Last modified October 14, 2003 by Jennifer Bergman.

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