asteroids

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Asteroids
	On the first night of the nineteenth century the first ever asteroid was discovered. It was detected by an Italian astronomer named Giuseppe Piazzi and was given the name Ceres after the Roman goddess of harvest. From the very beginning it was clear that Ceres was not a Planet. It isn’t bright enough to be seen with the naked eye and measures less than 600 miles across- about a quarter of the diameter of the Earth’s Moon. Piazzi referred to it as an asteroid, which means “starlike”, because it could only be seen as a small point of light in his telescope. Astronomers still use the term to this day but also refer to these objects as minor planets.
Soon other asteroids were discovered and were given names like Pallas, Vesta, and Juno, all of them smaller than Ceres. The total number of asteroids known to this day, counting those the size of small cars, exceeds 100,000. Most of these asteroids orbit somewhere between Mars and Jupiter. Out of the 100,000 known asteroids only fifteen are more than 150 miles across. It is a tradition to name astronomical objects after mythology. But as more and more asteroids were discovered names began to run out for them and, as a result of this they were given a number and a non-mythological name. The number indicates the order of the discovery and the name ranges anywhere from people to places, such as Chicago and California.
	At one point in time the idea was held that asteroids were once a part of a planet that blew up. But that notion soon vanished as little or no evidence could support that. If you were to combine all the known asteroids together you would have an object with less than one-tenth the mass of our Moon. The asteroids are quite possibly fragments of a planet that never came to be. Asteroids are pieces of material left over from the formations of the solar system. 4.6 billion years ago clouds of gas and dust began to form the sun and the planets of our solar system. Over time, grains of dust began to collide and stick together as the orbited the Sun. These “dust balls” began to grow larger as they collected more matter through their own increasing gravitational pull. The largest formed the planets and their satellites while the smaller pieces could not obtain a strong enough gravitational pull or were prevented from growing by the gravitational tugging of Jupiter. Over time these objects underwent numerous collisions with each other and became even smaller in size. In August 1993, Galileo came across Ida, which was a little over a mile across. It soon discovered that it had an object orbiting around it. This tempted scientists to name the smaller object “Ho” (as in Ida-Ho) but astronomers ended up settling on the name Dactyl.
Some asteroids share an orbit with Jupiter. The Trojan asteroids, as they’re called, share Jupiter’s orbit. One group orbits 60? ahead of the giant planet while the other group trails behind by 60?. Other groups of asteroids orbit close to Earth. The three families are Amors which orbit between Earth and Mars; the Athens, whose orbit can carry them between Earth and Venus: and the Apollos, whose orbits cross that of Earth. This of course leaves many scientists concerned. While none of the current Apollos appear to intersect with Earth their orbits are constantly changing as a result of the gravitational pull of the various planets. In the End, more than 1,000 known AAA objects could prove life threatening here on Earth. On average, estimates state that three Apollo asteroids strike the Earth every million years. Most near-Earth (Apollo) asteroids are less than 1 mile across but one has been found to be 6 miles in length. Jupiter can be considered the bully in all this. With its intense gravitational pull it easily disrupts asteroids or any other object near the planet, which redirects them to the inner solar system. This helped to create the craters we now see on the Moon, Mercury, and Mars.