Comets and asteroids fly by the Earth all of the time, and this week we are set to have another opportunity to see one of these amazing celestial events.
Comet 209P/LINEAR is a rather dim comet that orbits the Sun every 5 years. Although it frequently passes by the Earth, it's usually at a bit of a distance. However, this year it is set to be quite a bit closer. Ultimately, Jupiter (the largest planet in our solar system) is responsible for this show, as the planet flung the comet our way, causing it to fly by Earth at a distance of 5 million miles (8 million km). Anyone with a consumer model 3-inch-reflector telescope should be able to see the comet as it passes in the north sky Thursday morning, May 29, shortly before 2 a.m. MDT.
NASA meteor observer Bill Cooke offered some further insight into this event, asserting that, “Its core is 1 to 2 miles wide, and a direct hit to Earth would be disastrous.” Comets are, more or less, just asteroids that have tails. This is because comets are composed of dusty ice, and when they swing in close to the Sun, the ice heats up and trails away. As they orbit the Sun, comets leave a trail of dust and gas that is millions of kilometers/miles long. They are a bit smaller than asteroids; generally, they are the size of an average town, though the shining head of a comet (the coma) can be larger than a planet. Over many, many close passes to the Sun, a comet begins to look less like a comet and more like an asteroid (as its icy is worn away and its outgassing begins to halt).