A Close Encounter with an Asteroid

Path of 2002 NY40
Over four weeks, the brightness of 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. This chart will be updated prior to the asteroid's flyby of Earth.
S&T: Roger Sinnott and Gregg Dinderman.
An updated version of this article, complete with finder charts, is available here.

In mid-August an asteroid will pass close enough to Earth to be easily spotted in small telescopes and 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, 2002 NY40 is making a very tight loop around the star Beta Aquarii. During the next week 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.)

There is no danger of 2002 NY40 striking Earth during this flyby. Both NEODyS, operated by the University of Pisa, and NASA's Near-Earth Object Program have also ruled out an impact during the coming century.

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. Preliminary results indicate the asteroid takes longer than 24 hours to complete one rotation.

An Ephemeris for 2002 NY40

The following ephemeris, adapted from the Minor Planet Ephemeris Service, gives the asteroid's right ascension and declination at 0 hours Universal Time on successive dates. Also listed are its distance from the Earth (Delta) and Sun (r) in astronomical units, 1 a.u. being 149,600,000 kilometers. The last column is the predicted visual magnitude.

This table will be updated as improvements are made in the orbital calculations for 2002 NY40. Note that the object will be fainter than Pluto through the evening of August 12th; then it brightens VERY RAPIDLY.

Closer to the date of the actual flyby, Sky & Telescope is planning to publish a detailed finder chart for August 17th so observers can track the asteroid as it goes by some bright objects or stars.

Ephemeris of 2002 NY40
(0h UT)
R.A. (2000)
h   m
°   '
Aug 05 21 34.3 -04 37 0.163 1.173 16.1
Aug 06 21 34.0 -04 31 0.151 1.161 15.9
Aug 07 21 33.7 -04 24 0.138 1.149 15.6
Aug 08 21 33.4 -04 16 0.126 1.137 15.4
Aug 09 21 32.9 -04 08 0.113 1.125 15.1
Aug 10 21 32.3 -03 57 0.101 1.113 14.8
Aug 11 21 31.5 -03 44 0.089 1.101 14.5
Aug 12 21 30.5 -03 28 0.077 1.089 14.2
Aug 13 21 29.1 -03 06 0.065 1.077 13.8
Aug 14 21 27.0 -02 35 0.053 1.064 13.3
Aug 15 21 23.7 -01 44 0.040 1.052 12.8
Aug 16 21 17.6 -00 12 0.028 1.040 12.1
Aug 17 21 02.7 +03 33 0.017 1.028 11.0
Aug 18 19 33.5 +22 43 0.005 1.016 9.4
Aug 19 10 47.6 +21 15 0.009 1.004 21.0
Aug 20 10 05.9 +12 06 0.020 0.992 49.7
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