Tomorrow night, near-Earth asteroid 2005 YU55 will pass between our planet and the orbit of the moon, coming within 0.85 lunar distances of the Earth's surface as it courses along its orbit. Astronomers say the object, which measures about 400 meters in diameter, is the largest asteroid to fly this close to home in 35 years.
2005 YU55 is a type-c (i.e. carbonaceous) asteroid, meaning its surface is dark. This will make the asteroid impossible to see with the naked eye, but scientists say skywatchers with the right equipment should be able to catch a glimpse of the massive rock as it zips by Earth. Here's how you can spot it for yourself.
First of all, you're going to need the right equipment. Amateur skywatchers will need a telescope with at least a 6-inch mirror to spot the asteroid.
Next, you'll need to know when to look. NASA's estimates indicate that the asteroid's closest approach to Earth will occur tomorrow night at 23:28 UT, or 06.28 p.m. EST.
The object will likely be best seen from Western Europe and North America; according to Scott Fisher, program director of the National Science Foundation's Division of Astronomical Sciences, stargazers on the East Coast of the US will have the best shot of spying the object at its closest point of approach.
Finally, you'll need to know where to point your telescope. According to Sky & Telescope Magazine, 2005 YU55 will traverse the 70° of sky eastward from the constellation Aquila to central Pegasus in just 10 hours. This means it'll be moving at a pretty decent clip, which will likely make it harder to spot, but here's a detailed chart, along with instructions from Sky & Telescope on how to find the asteroid (click the image below to enlarge the chart):
Asteroid 2005 YU55 will race far across the constellations in just 11 hours. The box on the top chart [the dark blue constellation map with the yellow path line] shows the area of the closeup above. There, the asteroid is plotted for just over an hour on the evening of November 8th for North America (from 1:51 to 3:12 November 9th Universal Time). North is up, east is left. On each of the little upside-down maps of the U.S., put a pencil dot on your location. These are the asteroid's apparent positions at 2:00 and 3:00 UT for your site. Connect your dots with a straight line paralleling the line plotted, which is for Kansas.
Those with the astronomical know-how can look up the asteroid's coordinates for any given time on the JPL Solar System Dynamics website, and stargazing buffs with more high powered equipment (10—12 inch scopes, CCD cameras, profesional filters, etc.) are encouraged to help astronomers obtain more detailed brightness measurements of the asteroid (details can be found here).
That's all the general information you'll need to start your asteroid hunt. Don't forget to avoid light pollution whenever possible — you'll already be fighting the full moon to catch a glimpse of the asteroid.