Catch an Asteroid on the Fly
22 Jul 2002
(Source: Sky & Telescope)
This Is SKY & TELESCOPE's AstroAlert for Minor Planets
In mid-August, a newly discovered asteroid will pass close enough to Earth that it should be easy to spot in small telescopes and even binoculars. This object was first detected on July 14th by astronomers using the LINEAR 1-meter survey telescope in New Mexico, and it has now been designated 2002 NY40 by the Minor Planet Center in Cambridge, Massachusetts. According to calculations by the center's associate director, Gareth V. Williams, it is traveling in a low-inclination, Apollo-type orbit with a period of 3.03 years. Its August 18th flyby should bring it to within 530,000 kilometers (330,000 miles) of Earth, which is just outside the Moon's distance.
There are several key differences between this encounter and that of 2002 MN, which made news a few weeks ago. That object came well inside our own Moon's orbit and was not detected until several days after the fact. The new asteroid was found on its way in toward the Sun, a full month before its own flyby. But 2002 NY40 is about 10 times larger than 2002 MN; the best current estimates make it about half a kilometer (a third of a mile) across.
Still quite faint at magnitude 18 in the constellation Aquarius, 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 the Earth! Then it veers off to the northwest as it goes by, racing past the double star Albireo in Cygnus for observers in the Western Hemisphere on the night of August 17-18.
On that Saturday evening, 2002 NY40 should become as bright as magnitude 9.3 during the period when it is well placed for viewing from North America. 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, 2002 NY40 plunges hopelessly beyond reach of Earth-based telescopes as it heads in toward the Sun. (We are then viewing its unilluminated backside, which explains why it becomes so faint, so fast.) Meanwhile, professional astronomers are gearing up to make the most of this encounter. "2002 NY40 is a potentially very good radar target for mid-August," notes Mike Nolan of Arecibo Observatory and Cornell University. In a message posted on the Minor Planet Mailing List (http://www.bitnik.com/mp ), Nolan 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 instrumentation to be used with the Arecibo 1,000-foot radio dish.
While there is no danger of 2002 NY40 striking the 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 Office at JPL have identified a number of very close encounters in the years to come. These occur either around August 18th as the asteroid heads in toward the Sun, or else near February 14th when it is on the way out. Both agencies are focusing a flyby just 20 years from now (on August 18, 2022), when there appears to be a 1-in-500,000 chance of an impact -- extremely unlikely, but worrisome just the same.
Roger W. Sinnott
Senior Editor
Sky & Telescope
The following ephemeris, adapted from the Minor Planet Ephemeris Service at
http://cfa-www.harvard.edu/iau/mpc.html, gives the object's right ascension and declination at 0h 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.
Because this is a newly discovered object passing fairly close to the Earth, the ephemeris is still somewhat uncertain (especially on the final dates listed). Keep in mind that these positions are geocentric; parallax at closest approach could shift the object's position by 1/2 degree or more depending on observer's geographic location. (To display the ephemeris properly, your e-mail program should be set to use a fixed-space font such as Courier.)
Ephemeris of 2002 NY40
| Date
(oh UT) | ????? | R.A. (2000)
H????m???? | ????? | Decl.
o????' | ????? | Delta
a.u. | ????? | r
a.u. | ????? | V
mag. |
| Jul 22 | 21 | 33.8 | -05 | 46 | 0.347 | 1.336 | 18.2 |
| Jul 23 | 21 | 34.0 | -05 | 41 | 0.333 | 1.325 | 18.1 |
| Jul 24 | 21 | 34.1 | -05 | 37 | 0.319 | 1.313 | 18.0 |
| Jul 25 | 21 | 34.3 | -05 | 32 | 0.306 | 1.302 | 17.8 |
| Jul 26 | 21 | 34.4 | -05 | 27 | 0.292 | 1.290 | 17.7 |
| Jul 27 | 21 | 34.6 | -05 | 23 | 0.279 | 1.278 | 17.6 |
| Jul 28 | 21 | 34.6 | -05 | 18 | 0.266 | 1.267 | 17.4 |
| Jul 29 | 21 | 34.7 | -05 | 13 | 0.253 | 1.255 | 17.3 |
| Jul 30 | 21 | 34.8 | -05 | 09 | 0.240 | 1.243 | 17.1 |
| Jul 31 | 21 | 34.8 | -05 | 04 | 0.227 | 1.232 | 17.0 |
| Aug 01 | 21 | 34.7 | -04 | 59 | 0.214 | 1.220 | 16.8 |
| Aug 02 | 21 | 34.7 | -04 | 54 | 0.201 | 1.208 | 16.6 |
| Aug 03 | 21 | 34.6 | -04 | 49 | 0.188 | 1.196 | 16.5 |
| Aug 04 | 21 | 34.5 | -04 | 43 | 0.176 | 1.185 | 16.3 |
| 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 | 46 | 0.040 | 1.052 | 12.8 |
| Aug 16 | 21 | 17.7 | -00 | 16 | 0.028 | 1.040 | 12.1 |
| Aug 17 | 21 | 03.1 | +03 | 23 | 0.017 | 1.028 | 11.0 |
| Aug 18 | 19 | 39.2 | +22 | 26 | 0.005 | 1.016 | 9.4 |
| Aug 19 | 10 | 50.2 | +21 | 39 | 0.009 | 1.004 | 21.0 |
| Aug 20 | 10 | 06.4 | +12 | 09 | 0.020 | 0.992 | 49.7 |
