Monday, June 27, 2011

Asteroid

Asteroid Passes Earth Closer Than The Moon

An asteroid zoomed past Earth this morning, coming within 7,500 miles above Earth's surface over the southern Atlantic Ocean.

2011 MD, as the asteroid is named, did not come as close to Earth as a smaller asteroid, 2011 CQ1, which avoided an impact with the planet by just 3,405 miles in February.

Even so, 2011 MD flew closer to Earth than the moon.

The latest asteroid is 33 feet long and was discovered this week by telescopes in New Mexico, the AP reports.

According to the IBTimes, 2011 MD is the 5th-closest asteroid to zip past Earth.

Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones. These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System were discovered, their volatile-based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids.

Thus the term asteroid has come increasingly to refer specifically to the small rocky–icy and metallic bodies of the inner Solar System out to the orbit of Jupiter. These are grouped with those outer bodies—centaurs, Neptune trojans, and trans-Neptunian objects—as minor planets, which is the term preferred in astronomical circles. This article will restrict the word 'asteroid' to the minor planets of the inner Solar System.

There are millions of asteroids, and like most other small Solar System bodies, asteroids are thought to be the often shattered remnants of planetesimals, bodies within the young Sun’s solar nebula that never grew large enough to become planets. A large majority of known asteroids orbit in the main asteroid belt between the orbits of Mars and Jupiter or co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth asteroids. Individual asteroids are classified by their characteristic spectra, with the majority falling into 3 main groups: C-type, S-type, and M-type. These were named after and are generally identified with carbon-rich, stony, and metallic compositions, respectively.

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