Aircraft Carrier-Sized Astroid 2005 YU55 Will Make Its Closest Pass by Earth Today

Today, the Earth will have a close encounter with an astroid the size of a city block. But don't worry, it's only "close" in relation to the size of the universe; it will still be about 201,700 miles away from the planet we call home.

NASA insists that the astroid will miss the Earth. The space agency has been tracking the astroid, along with thousands of other "Near-Earth Objects", since it was first spotted six years ago. It's path is well-known.

Don Yeomans, manager of NASA's Near Earth Object Program at the Jet Propulsion Laboratory in California said:

"We're extremely confident, 100 percent confident, that this is not a threat. But it is an opportunity."

The 2005 YU55 astroid is a C-type astroid, which means it is rich in carbon-based molecules. It is hypothesized that billions of years ago when the solar system was new and full of debris, astroids similar to it likely crashed into the young Earth routinely, carrying with them organic, carbon-based materials, which makes life possible. Scientists would like to probe the astroid's chemical makeup, even if its only remotely.

The astroid is at least 1,300 feet wide, which is larger than an aircraft carrier, and is moving about 29,000mph relative to Earth's surface. The last time that an astroid of this size passed by Earth was in 1976. The next one of a similar size isn't expected to pass Earth until 2028.

Astroids will often pass the Earth this close, but most of them are rather tiny.

So what would happen if the scientists were wrong, and 2005 YU55 came crashing into the Earth's atmosphere? Jay Melosh, a professor of Earth and atmospheric sciences at Purdue University, has done some calculations. He says that if the astroid were to hit us, it would blast out a crater 4 miles across and 1,700 feet deep. That would shake the Earth like a magnitude 7 earthquake and would likely result in 70-foot-high tsunami waves.

For such a large astroid, however, it wil not be visible to the naked eye when it passes by Earth at 6:28pm ET. At its brightest point it will look like a magnitude 11 star, which is 100 times dimmer than the limit of human vision if looking at the night sky from a dark place with clear weather. Alan MacRobert of Sky & Telescope magazine says that "you should be able to spot the astroid with your telescope if it has an aperture of at least 6 to 8 inches."

After astroid 2005 YU55 passes the earth, it will disappear out into the universe, continuing its elliptical orbit that will take it as close to the sun as Venus and as far away as Mars.