what is an asteroid?

Answer 1

Sumit is wrong. Meteor showers are the result of the earth passing through the dust and debris left behind in the wake of a comet. eg The Perseids every August are the debris left by Comet Hale-Tuttle, The size of the particles is tiny, the size of a grain of sand.

Asteroids are somewhat larger than that and if one came near earth and entered the atmosphere it would cause considerable damage.

It is believed that the dinosaur extinction was caused by the after-effects of an asteroid impact and the atmosphere being choked up with dust and debris for centuries afterwards.

The term asteroid (meaning star-like) was coined by Sir William Herschel in 1802 when Ceres and Pallas the first two Trans-Martian cis-Jovian objects were discovered and classified as planets (as were 3 Juno (in 1804)and 4 Vesta (in 1807) for lack of any other category to put them in. Herschel felt that both Ceres and Pallas were disappointingly small to be thought of as planets and so came up with a term to describe them.

By the mid-19th Century as more and more such objects between Mars and Jupiter were discovered, Ceres, Pallas Juno and Vesta were downgraded to asteroid status and the process of distinguishing minor and major planets had begun in earnest.

We now know of nearly 340,000 asteroids and it is believed there may be over a million of them. Some of them have moons. 87 Sylvia has two of them. Some are binaries eg 90 Antiope, The first moon of an asteroid to be discovered (1994) was Dactyl, orbiting 243 Ida.

The 20 Largest known asteroids with diameters in kilometres

1 Ceres 975×909
4 Vesta 578×560×458
2 Pallas 570×525×500
10 Hygiea 500×385×350
511 Davida 326
704 Interamnia 317
52 Europa 360×315×240
624 Hektor 370×195
15 Eunomia 330×245×205
3 Juno 290×240×190
87 Sylvia 261
31 Euphrosyne 256
16 Psyche ~280×230×190
65 Cybele 237
107 Camilla 340×230×140
121 Hermione 265×180×180
9 Metis 235×195×140
324 Bamberga 229
24 Themis 228

As of the IAU decision of a week ago the term asteroid will not be used in future but "small Solar System bodies" (SSSBs) will be used instead and that category will include comets.

52 Europa shares its name with a moon of Jupiter as does 85 Io. To avoid confusion the prefixes 52 and 85 need to be affixed to make it clear it is the asteroid of that name that is being referred to.

Answer 2

Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. They are known as minor planets. Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. Sixteen asteroids have a diameter of 240 km or greater. They have been found inside Earth's orbit to beyond Saturn's orbit. Most, however, are contained within a main belt that exists between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path and some have even hit the Earth in times past. One of the best preserved examples is Barringer Meteor Crater near Winslow, Arizona.


Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across -- less than half the diameter of our Moon.

Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite.

Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials. Stony meteorites are the hardest to identify since they look very much like terrestrial rocks.

Because asteroids are material from the very early solar system, scientists are interested in their composition. Spacecraft that have flown through the asteroid belt have found that the belt is really quite empty and that asteroids are separated by very large distances. Before 1991 the only information obtained on asteroids was though Earth based observations. Then on October 1991 asteroid 951 Gaspra was visited by the Galileo spacecraft and became the first asteroid to have hi-resolution images taken of it. Again on August 1993 Galileo made a close encounter with asteroid 243 Ida. This was the second asteroid to be visited by spacecraft. Both Gaspra and Ida are classified as S-type asteroids composed of metal-rich silicates.

On June 27, 1997 the spacecraft NEAR made a high-speed close encounter with asteroid 253 Mathilde. This encounter gave scientists the first close-up look of a carbon rich C-type asteroid. This visit was unique because NEAR was not designed for flyby encounters. NEAR is an orbiter destined for asteroid Eros in January of 1999.

Astronomers have studied a number of asteroids through Earth-based observations. Several notable asteroids are Toutatis, Castalia, Geographos and Vesta. Astronomers studied Toutatis, Geographos and Castalia using Earth-based radar observations during close approaches to the Earth. Vesta was observed by the Hubble Space Telescope.

Answer 3

Asteroids r rocky masses floating in free space,generally orbiting the Sun with very high speeds.Their size may vary frm a few centimtrs to 1or 2 kilomtrs.
When an asteroid enters the earth's atmosphere(with high speed) it starts burning due to huge amount of heat energy generated by friction (as it collides with air particles).Such a burning asteroid is called a Meteorite.
In India, when someone see such a scene ,he says "Broken Star is falling!!".....

Answer 4

An asteroid is a chuck of rock or debris floating in space, usually orbiting the sun. When an asteroid encounters a planet (such as Earth), it is then called a meteor.

Answer 5

Asteroid (Greek for "star-like") is the word used most in the English literature for minor planets, which was the term preferred by the International Astronomical Union until recently; other languages prefer planetoid (Greek: "planet-like"). In late August 2006, the IAU switched to the term "small solar system bodies" (SSSBs, which includes comets) whilst simultaneously introducing "dwarf planet". Asteroid, minor planet, and planetoid are synomyms, and are used to indicate a diverse group of small celestial bodies that drift in the solar system in orbit around the Sun. This Wikipedia article treats the minor planets that orbit in the inner solar system (roughly up to the orbit of Jupiter), and that probably have mostly a "rocky" composition. For other types of objects, such as comets, Trans-Neptunian objects, and Centaurs, see Small solar system body.

In our Solar System, the first discovered and largest asteroid Ceres is now classified as a dwarf planet, while all the rest are currently classified as small solar system bodies. The vast majority of the asteroids are found within the main asteroid belt, with elliptical orbits between those of Mars and Jupiter. It is thought that asteroids are remnants of the protoplanetary disc, and in this region the incorporation of protoplanetary remnants into the planets was prevented by large gravitational perturbations induced by Jupiter during the formative period of the solar system. Some asteroids have moons or are found in pairs known as binary systems.

Hundreds of thousands of asteroids have been discovered within the solar system and the present rate of discovery is about 5000 per month. As of July 23, 2006, from a total of 338,186 registered minor planets, 134,339 have orbits known well enough to be given permanent official numbers. Of these, 13,242 [1]have official names (trivia: about 650 of these names require diacritics). The lowest-numbered but unnamed minor planet is (3360) 1981 VA; the highest-numbered named minor planet is 129342 Ependes [2].

Current estimates put the total number of asteroids above 1 km in diameter in the solar system to be between 1.1 and 1.9 million[3]. The largest asteroid in the inner solar system is 1 Ceres, with a diameter of 900-1000 km. Two other large inner solar system belt asteroids are 2 Pallas and 4 Vesta; both have diameters of ~500 km. Vesta is the only main belt asteroid that is sometimes visible to the naked eye (in some very rare occasions, a near-Earth asteroid may be visible without technical aid; see 99942 Apophis).

The mass of all the asteroids of the Main Belt is estimated to be about 3.0-3.6×1021 kg[4][5], or about 4% of the mass of our moon. Of this, 1 Ceres comprises 0.95×1021 kg, some 32% of the total. Adding in the next three most massive asteroids, 4 Vesta (9%), 2 Pallas (7%), and 10 Hygiea (3%), bring this figure up to 51%; while the three after that, 511 Davida (1.2%), 704 Interamnia (1.0%), and 3 Juno (0.9%), only add another 3% to the total mass. The number of asteroids then increases exponentially as their individual masses decrease

Answer 6

i'm not conscious of the magnitude, the two, yet mine is placed in Gemini at sixteen ranges. Gemini additionally happens to be my descendant. Hmm. Edit: If the belief is that even though sign the Asteroid Nemesis be placed in is indicative of the characteristics of an actually nemesis, then i could prefer to function some extra words. i understand few Gemini suns, yet i'm surrounded with the help of many that've heavily aspected Mercuries, and an abundance of third domicile/Gemini placements. i for my section appreciate this form, incredibly; yet as quickly as I ever have a difficulty with somebody, it rather is often through a loss of self-discipline, on their section, whilst it contains speaking. I have not got any tolerance for verbal attacking, severe swearing, and no admire for people who have faith they are intellectually extra advantageous and make the main others through fact of it. The few persons in existence that I even have deemed a waste of time have had this difficulty, and a remark for each thing- an excellent larger difficulty. it fairly is those individuals who do not hear that don't study. not my difficulty, besides, eh? Is there a link for this information everywhere? This rather became thrilling.

Answer 7

An asteroid is a small body orbiting the sun that is usually irregularly shaped. It may also be called a planetoid or minor planet.

Answer 8

Any of numerous small celestial bodies that revolve around the sun, with orbits lying chiefly between Mars and Jupiter and characteristic diameters between a few and several hundred kilometers. Also called minor planet, planetoid

Answer 9

they r cosmic bodies of size smaller than the planets, mostly found between the orbits of mars and jupiter