Union observes landmark asteroid


By Tokuei Higashino


A small group of students and professors working with the 20- inch reflecting telescope at the Union Observatory managed to photograph an asteroid that passed closer to the Earth than our own moon on Tuesday, Nov. 8.

The space rock, known as 2005 YU55 after its discovery by Robert McMillan of the NASA Spacewatch project six years ago, has a diameter of approximately 400 meters (1,300 feet), slightly larger than the height of the Empire State Building.

Asteroids often pass near the Earth, but most are much smaller.

“A direct hit by the asteroid could have been devastating to a populated area, but the Earth was not in any danger, as the asteroid’s orbit is well understood for the near future,” explained Professor Francis Wilkin.

Students from Wilkin’s Astronomy 51 and Astronomy 230 courses were joined by Professor George Shaw of the Geology Department to take a series of 24 images at about 10 p.m.

At the time of observations, the object was about 319,000 kilometers (200,000 miles) from Earth; this distance is the closest it has been to Earth for at least the last 200 years.

For comparison, the moon’s average distance from Earth is approximately 384,400 kilometers (238,900 miles).

Photographing the asteroid is no simple task; due to its rapid motion, the biggest challenge during observations was locating the asteroid in the sky.

Each exposure required quick adjustments in the telescope pointing to keep the asteroid inside the image frame, since the asteroid moved about 20 percent of the way across the field of view during a 20 second exposure with a special camera.

Fortunately for us, the asteroid’s near pass has little effect on Earth.

The gravitational pull of the asteroid is far too weak to have a detectable effect on anything on Earth, such as tides or tectonic plates.

Events like this don’t happen every day, but close flybys be asteriods aren’t uncommon, either. A similarly sized space rock came just as close in 1976, and the next approach of a space rock this large is expected in 2028.


Leave a Reply