On December 10, 2010, Russian astronomer, Leonid Elenin, discovered a comet at the International Scientific Optical Network's robotic observatory near Mayhill, New Mexico. This comet, named Elenin, is heading to the inner-solar system in September 2011. So what is a comet and what does that mean for us?
Comets are the left overs from star formations and from planets billions of years ago. Referred to as "dirty snowballs," they started out as big chunks of rock and ice. These chunks floated around the Oort Cloud (an immense spherical cloud surrounding the planetary system extending roughly three light years from the Sun). When gravity from a star gets strong enough, some of the large chunks of ice pull away from the cloud and start toward the Sun. The closer it gets to the Sun, the ice starts to melt. The tail you see at the end of a comet is actually a gaseous tail. This tail extends away from the Sun, the source of heat. The closer a comet comes to the Sun, the faster it moves. The tail of the comet will continue to grow in length due to more of the ice evaporating.
Elenin will come 21 million miles near the Earth. The speed of the comet will enable it to travel the Earth to the moon under five hours. According to Astrobiology Senior Scientist, David Morrison, NASA, the mass of Elenin is " less than one billionth the mass of the Earth". People have wondered if the comets magnetic fields will cause earthquakes, floods or knock the Earth off its axis. "Comets don't have magnetic fields, and magnetic fields can't change the rotation axis or cause earthquakes no matter how large they are." David Morrison, Astrobiology, Senior Scientist.
Although comets are not uncommon, in 1770 the comet, Lexell, was the closest ever recorded to come close to the Earth. Lexell passed at 1.4 million miles. January 26th that year, just off the west coast of North America, a 9.0 earthquake happened.
What is the difference between an asteroid and a comet? Asteroids are chunks of rock measuring from a few feet to several miles in diameter. Most asteroids lie between Mars and Jupiter in the asteroid belt. Comets are balls of ice and rock. As they approach the Sun they grow tails. When comets get hot, a trail of dust and gas come from them. The Sun causes the trail to glow. In the evening hours the trail is most visible.
It is believed an asteroid is the cause of extinction of the dinosaurs 65 million years ago, when it slammed into Earth. There is still a chance that one day Earth could be hit by another asteroid. A comet exploded in Siberia in 1908, causing damage to farmland and destroying trees for miles around. Estimations are an asteroid would be expected to hit the Earth every 100 million years or so. The Lincoln Near-Earth Asteroid Research (LINEAR) project at the Massachusetts Institute of Technology monitor potential Earth bound asteroids.
The comet Elenin will be closest to the Sun in early September. It will be 40 -45 million miles from the Sun. The closest it will be to the Earth will be around October 16th. It is expected during August and October 2011, Elenin will be visible using binoculars.