Other Celestial Objects Comets Asteroids Meteors and Meteorites

Other Celestial Objects Comets, Asteroids, Meteors, and Meteorites

Comets n A comet is sometimes called a “dirty snowball”. n It is a mixture of frozen water, gases and dust. n A comet is invisible except when it is near the Sun. n A comet has a very eccentric orbit. The orbit is tilted off of the solar plane.

A Comet’s Tail n As it approaches the Sun, a tail, millions of km long becomes visible. n A comet’s tail will always face away from the Sun as it is created by the solar wind from the Sun. n http: //www. windows. ucar. ed u/tour/link=/comets/comet_m odel_interactive. html n http: //www. esa. int/SPECIAL S/Rosetta/SEM 3 NV 0 PGQD_ 0. html

Asteroids n Most asteroids are found in the asteroid belt, between Mars and Jupiter. n They have a rocky composition. n The largest asteroid Ceres was promoted to dwarf planet status.

Meteoroid A meteoroid is a rock travelling through space but has yet to reach the Earth’s atmosphere.

Meteors n A meteor is a bright streak of light in the sky (a shooting star or a falling star) produced when a small meteroroid enters the Earth’s atmosphere. n Most meteoroids are small and burn up due to the heat of friction through the atmosphere.

A Meteor’s Orbit n If you have a dark clear sky, on an average night, you will probably see a few meteors per hour. n During one of the annual meteor showers you may see as many as 100/hour.

Meteorites Only the largest meteors can survive travelling through Earth’s atmosphere and fall to Earth as meteorites.

The Hoba Meteorite The Hoba meteorite is the largest meteorite to be discovered. It was found in Namibia, Africa This nickle-iron meteorite was slowed down to free fall velocity and thus it was not destroyed on impact and did not leave an impact crater. They've cut away the earth around it, but what you see here is the depth it was found at, being that it has never been moved. While it weighed an estimated 66 tons when found in 1920, it has now rusted away to 60 tons. This is also the largest piece of natural iron we've found on earth.

Meteorite Craters n Only meteoroids larger than a few hundred tons can survive and hit Earth, leaving a crater. n This crater is the Barringer Crater, near Winslow, Arizona. It was formed 50, 000 years ago by an iron meteor about 30 -50 m in diameter. n The crater is 1200 m in diameter and 200 m deep. n About 120 impact craters have been identified on the Earth.

Tunguska Event http: //news. nationalgeographic. com/news/2007/ 11/071107 -russia-crater. html