tell me everything you know about asteroids!!!!!!!?

Answer 1

INTRODUCTION

Asteroid, one of the many small or minor rocky planetoids that are members of the solar system and that move in elliptical orbits primarily between the orbits of Mars and Jupiter.

SIZES AND ORBITS

The largest object in the asteroid belt is 1 Ceres, with a diameter of about 950 km (about 590 mi). Ceres was long considered to be an asteroid but in 2006 the International Astronomical Union (IAU) reclassified Ceres as a dwarf planet because it has been shaped into a spheroid by its own gravity. (To qualify as a true planet Ceres would need to have cleared the neighborhood of its orbit (the asteroid belt) of other bodies.) The IAU still lists 1 Ceres as a minor planet along with asteroids. The next largest objects in the asteroid belt are 2 Pallas and 4 Vesta, with diameters of about 530 km (about 329 mi).

The naming of asteroids and other solar system bodies is governed by the IAU. After an astronomer observes a possible unknown asteroid, other astronomers confirm the discovery by observing the body over a period of several orbits and comparing the asteroid’s position and orbit to those of known asteroids. If the asteroid is indeed a newly discovered object, the IAU gives it a number according to its order of discovery, and the astronomer who discovered it chooses a name. Asteroids are usually referred to by both number and name.

About 200 asteroids have diameters of more than 97 km (60 mi), and thousands of smaller ones exist. The total mass of all asteroids in the solar system is much less than the mass of the Moon. The larger bodies are roughly spherical, but elongated and irregular shapes are common for those with diameters of less than 160 km (100 mi). Most asteroids, regardless of size, rotate on their axes every 5 to 20 hours. Certain asteroids may be binary, or have satellites of their own.

Few scientists now believe that asteroids are the remnants of a former planet. It is more likely that asteroids occupy a place in the solar system where a sizable planet could have formed but was prevented from doing so by the disruptive gravitational influences of the nearby giant planet Jupiter. Originally perhaps only a few dozen asteroids existed, which were subsequently fragmented by mutual collisions to produce the population now present. Scientists believe that asteroids move out of the asteroid belt because heat from the Sun warms them unevenly. This causes the asteroids to drift slowly away from their original orbits.

The so-called Trojan asteroids lie in two clouds, one moving 60° ahead of Jupiter in its orbit and the other 60° behind. Astronomers have recently found another group of Trojan asteroids that share Neptune’s orbit, possibly representing a population several times larger than the Jupiter Trojans. In 1977 the asteroid 2060 Chiron was discovered in an orbit between that of Saturn and Uranus. Asteroids that intersect the orbit of Mars are called Amors; asteroids that intersect the orbit of Earth are known as Apollos; and asteroids that have orbits smaller than Earth’s orbit are called Atens. One of the largest inner asteroids is 433 Eros, an elongated body measuring 13 by 33 km (8 by 21 mi). The peculiar Apollo asteroid 3200 Phaethon, about 5 km (about 3 mi) wide, approaches the Sun more closely, at 20.9 million km (13.9 million mi), than any other known asteroid. It is also associated with the yearly return of the Geminid stream of meteors (see Geminids).

Several Earth-approaching asteroids are relatively easy targets for space missions. In 1991 the United States Galileo space probe, on its way to Jupiter, took the first close-up pictures of an asteroid. The images showed that the small, lopsided body, 951 Gaspra, is pockmarked with craters, and revealed evidence of a blanket of loose, fragmental material, or regolith, covering the asteroid’s surface. Galileo also visited an asteroid named 243 Ida and found that Ida has its own moon, a smaller asteroid subsequently named Dactyl. (Dactyl’s official designation is 243 Ida I, because it is a satellite of Ida.)

In 1996 the National Aeronautics and Space Administration (NASA) launched the Near-Earth Asteroid Rendezvous (NEAR) spacecraft. NEAR was later renamed NEAR Shoemaker in honor of American scientist Eugene M. Shoemaker. NEAR Shoemaker’s goal was to go into orbit around the asteroid Eros. On its way to Eros, the spacecraft visited the asteroid 253 Mathilde in June 1997. At 60 km (37 mi) in diameter, Mathilde is larger than either of the asteroids that Galileo visited. In February 2000, NEAR Shoemaker reached Eros, moved into orbit around the asteroid, and began making observations. The spacecraft orbited the asteroid for a year, gathering data to provide astronomers with a better idea of the origin, composition, and structure of large asteroids. After NEAR Shoemaker’s original mission ended, NASA decided to attempt a “controlled crash” on the surface of Eros. NEAR Shoemaker set down safely on Eros in February 2001—the first spacecraft ever to land on an asteroid.

In 1999 Deep Space 1, a probe NASA designed to test new space technologies, flew by the tiny asteroid 9969 Braille. Measurements taken by Deep Space 1 revealed that the composition of Braille is very similar to that of 4 Vesta. Scientists believe that Braille may be a broken piece of Vesta or that the two asteroids may have formed under similar conditions.

The Japanese Hayabusa space probe reached the near-Earth asteroid Itokawa in September 2005 and orbited the 540-m (1171-ft)-long body for three months, taking detailed images, and studying the asteroid’s mass and surface environment. The images and data indicate that Itokawa is a loose pile of rubble rather than a solid body and consists of material that ranges in size from sand-like grains up to rocks 50 m (170 ft) wide. The probe also descended to the surface twice to attempt to collect samples of the asteroid. When Hayabusa returns to flyby Earth in 2010, it is scheduled to eject a canister containing the samples. If all goes as planned, the canister will enter the Earth’s atmosphere and land by parachute in Australia, providing the first direct samples of an asteroid.

NASA is planning the first mission to provide a detailed study of some of the largest objects in the asteroid belt. The Dawn spacecraft is scheduled for launch in 2007 and is expected to orbit Vesta in 2011 and Ceres in 2015. The two bodies are thought to represent different evolutionary stages in the formation of rocky planets from primitive materials in the early solar system.

III. SURFACE COMPOSITION

With the exception of a few that have been traced to the Moon and Mars, most of the meteorites recovered on Earth are thought to be asteroid fragments. Remote observations of asteroids by telescopic spectroscopy and radar support this hypothesis. They reveal that asteroids, like meteorites, can be classified into a few distinct types.

Three-quarters of the asteroids visible from Earth, as well as the dwarf planet 1 Ceres, belong to the C type, which appear to be related to a class of stony meteorites known as carbonaceous chondrites. These meteorites are considered the oldest materials in the solar system, with a composition reflecting that of the primitive solar nebula. Extremely dark in color, probably because of their hydrocarbon content, they show evidence of having adsorbed water of hydration. Thus, unlike the Earth and the Moon, they have never either melted or been reheated since they first formed.

Asteroids of the S type, related to the stony iron meteorites, make up about 15 percent of the total population. Much rarer are the M-type objects, corresponding in composition to the meteorites known as “irons.” Consisting of an iron-nickel alloy, they may represent the cores of melted, differentiated planetary bodies whose outer layers were removed by impact cratering.

A very few asteroids, notably 4 Vesta, are probably related to the rarest meteorite class of all: the achondrites. These asteroids appear to have an igneous surface composition like that of many lunar and terrestrial lava flows. Thus, astronomers are reasonably certain that Vesta was, at some time in its history, at least partly melted. Scientists are puzzled that some of the asteroids have been melted but others have not. One possible explanation is that the early solar system contained certain concentrated, highly radioactive isotopes that might have generated enough heat to melt the asteroids.

ASTEROIDS AND EARTH

Astronomers have found more than 300 asteroids with orbits that approach Earth’s orbit. Some scientists project that several thousand of these near-Earth asteroids may exist and that as many as 1,500 could be large enough to cause a global catastrophe if they collided with Earth. Still, the chances of such a collision average out to only one collision about every 300,000 years.

Answer 2

Asteroids, also called minor planets or planetoids, are a class of astronomical object. The term asteroid is generally used to indicate a diverse group of small celestial bodies that drift in the solar system in orbit around the Sun. Asteroid (Greek for "star-like") is the word used most in the English literature for minor planets, which has been the term preferred by the International Astronomical Union; some other languages prefer planetoid (Greek: "planet-like"), because it more accurately describes what they are. In late August 2006, the IAU introduced the term "small solar system bodies" (SSSBs), which includes most objects thusfar classified as minor planets, as well as comets. At the same time they introduced the term dwarf planet for the largest minor planets. This article deals specifically with the minor planets that orbit in the inner solar system (roughly up to the orbit of Jupiter). For other types of objects, such as comets, Trans-Neptunian objects, and Centaurs, see Small solar system body.

The first asteroid to be discovered in the Solar System, Ceres, is the largest asteroid known to date and is now classified as a dwarf planet. All others are currently classified as small solar system bodies. The vast majority of asteroids are found within the main asteroid belt, with elliptical orbits between those of Mars and Jupiter. It is thought that these 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.

Answer 3

asteroids are big rocks in the Solar system made by destructing of a planet between Mars and Jupiter,It was probably because of strong gravity of Jupiter.Now they are asteroid belt in the same place,If some bigger asteroid hits at Earth it would be the end of the human race.And if you wanna know,astronomy is my middle name.Ceres is the biggest asteroid in the solar system

Answer 4

there where two schools in london. the best members of those two schools were selected and were divided in 2 groups. both studied over asteroid and came up with 2 conclusion
1) they are the pieces of planet which broke due to collision with jupiter.
2) they are the rocks which failed to become planet. i.e. it is believed that all the planet are formed when many rocks came together, but asteroid are those rocks which due to gravitational pull of jupiter failed to come all together.
I THINK YOU MANY TIMES WONDER THAT WHY ALL THE PLANETS, STARS, MOON ARE IN THE SHAPE OF SPHERE OR THEY ARE ELLIPTICAL? IF YOU WANT THE ANSWER THEN GIVE ME TEN POINTS.

Answer 5

Asteroids are small celestial bodies resembling stars mostly found in the region of interplanetary space of orbits between Jupiter and Mars.

Answer 6

I think the question was everything YOU know, not what Google knows....

Asteroids are irregular shaped minor planets that do not have to be in any particular orbit.

Answer 7

I think that's just another name for hemorrhoids.

Answer 8

this is pretty comprehensive

http://en.wikipedia.org/wiki/Asteroid