Hefty Asteroid to Sweep Near Earth

By: Roger W. Sinnott July 23, 2003 0

Over four weeks, asteroid 2002 NY40 will brighten by more than 3,000 times. It will peak at magnitude 9.3 (bright enough to be seen through a small telescope or large binoculars) as it drifts rapidly through the northern Milky Way on the night of August 17–18. Tick marks indicate 0 hours Universal Time on the given date.

S&T: Roger Sinnott and Gregg Dinderman.

Next month a newly discovered asteroid will pass close enough to Earth to be easily spotted in small telescopes and even binoculars. According to calculations by Gareth V. Williams, associate director of the Minor Planet Center in Cambridge, Massachusetts, the asteroid's August 18th flyby should bring it to within 530,000 kilometers (330,000 miles) of Earth, just outside the Moon's orbital distance.

Astronomers first detected this object, designated 2002 NY40, on July 14th with the 1-meter LINEAR telescope in New Mexico. Thus it was picked up a full month before brushing by Earth, unlike asteroid 2002 MN, whose pass well inside the Moon's orbit was not realized until several days after the fact. The best current estimates suggest that this new interloper is about 500 meters (0.3 mile) across — significantly larger than 2002 MN.

Still quite faint at magnitude 18, 2002 NY40 is making a very tight loop around the star Beta Aquarii. During the next few weeks it will brighten tremendously and yet remain almost motionless in the sky — the eerie signature of an asteroid hurtling right toward Earth! On the night of Saturday, August 17th, 2002 NY40 should reach magnitude 9.3 when well placed for viewing from North America. At that time its angular velocity will exceed 4 arcminutes per minute, a motion easily perceptible in small telescopes. Sky & Telescope plans to issue detailed observing instructions, through AstroAlerts and SkyandTelescope.com, in the days leading up to this rare event.

A mere 24 hours after it goes by, the asteroid plunges hopelessly beyond reach of Earth-based telescopes as it heads closer to the Sun. (We will then be viewing its unilluminated side, which explains why it becomes so faint, so fast.)

While there is no danger of 2002 NY40 striking Earth during this flyby, a future impact has not been ruled out. Both NEODyS, operated by the University of Pisa, and NASA's Near-Earth Object Program have identified a small (1-in-many-million) chance of an impact on February 13, 2052.

Meanwhile, professional astronomers are gearing up to make the most of this encounter. "2002 NY40 is a potentially very good radar target," notes Michael Nolan (Cornell University). He urges advanced amateurs to obtain detailed photometry of the asteroid on the nights leading up to the flyby. A good light curve, revealing the object's rotation rate, would help in selecting the radar instrumentation to be used with the 1,000-foot dish at Arecibo, Puerto Rico.