Asteroid 2005 YU55

This radar image of asteroid 2005 YU55 was obtained on Nov. 7, 2011, at 11:45 a.m. PST (2:45 p.m. EST/1945 UTC), when the space rock was at 3.6 lunar distances, which is about 860,000 miles, or 1.38 million kilometers, from Earth.  Image credit: NASA/JPL-Caltech

NASA’s Deep Space Network antenna in Goldstone, Calif. has captured new radar images of Asteroid 2005 YU55 passing close to Earth.

The asteroid will safely fly past our planet slightly closer than the moon’s orbit on Nov. 8. The last time a space rock this large came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this size will be in 2028.

Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin Nov. 8, the same day the asteroid will make its closest approach to Earth at 3:28 p.m. PST (6:28 p.m. EST/1128 UTC).

trajectory of Asteroid 2005 YU55

The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach, it will be no closer than 201,700 miles (324,600 kilometers) as measured from the center of Earth, or about 0.85 times the distance from the moon to Earth.  The gravitational influence of the asteroid will have no detectable effect on Earth, including tides and tectonic plates. Although the asteroid is in an orbit that regularly brings it to the vicinity of Earth, Venus and Mars, the 2011 encounter with Earth is the closest it has come for at least the last 200 years.

To determine where to look, SKY & TELESCOPE’s editors have prepared two detailed finder charts. The first gives a general sense of where to look, and the second provides a detailed view to use while outside with your telescope. Once you’ve aimed at exactly the right spot, you shouldn’t have much trouble telling which starlike point is 2005 YU55. It will be gliding fast enough to move along in real time as you watch using a moderately high-magnification eyepiece.

“As it passes Earth, the asteroid gets so close that its position among the stars will be significantly affected by your location,” explains MacRobert. So the magazine’s detailed finder chart takes this parallax effect into account, by including small upside-down maps of the United States that permit you to establish the correct path for your location.

Discovered nearly six years ago by Robert McMillan at Steward Observatory’s Spacewatch Telescope in Arizona, 2005 YU55 has been this way before. In April 2010, it ventured close enough for detailed radar probing by the giant radio dish at Arecibo, Puerto Rico. It also approached even closer in 1976, though it went by undetected.

Asteroid 2005 YU55