Asteroid buzzes Earth in range of amateur 'scopes
BY MARK ARMSTRONG
Posted: 31 May 2013
It's a pretty rare event for astronomers to get a leisurely look over the course of a week at a Near-Earth-Object (NEO) making a close approach to our home planet. NEO 285263 (1998 QE2) buzzes us on the night of 31 May, closing to within 5.8 million kilometres (3.6 million miles) of Earth. At 15.2 lunar distances, that is very close by Solar System standards, although no where near as close as 2012 DA14's 27,000 km (17,200 miles) pass which gave Earth a very close shave back in February. Thankfully this minor planet or asteroid, like DA14, poses no threat to the Earth this time, and this is as close as it will come to us for at least the next 200 years.
1998 QE2 was discovered by MIT's LINEAR program on 19 August 1998, one of a shed-load of minor planets of diverse sizes, masses and orbits discovered every year by vigilant astronomers. The QE2 in its name is not a tribute to the famous Cunard liner, merely the way the Minor Planet Centre gives temporary designations to bodies discovered until there is sufficient data obtained to nail down its orbital parameters and predict with great accuracy it's position for any future date. According to the Jet Propulsion Laboratory 1998 QE2 is a 2.7-km ball of rock about nine times the size of its cruise liner name sake.
Observers in the UK have less than ideal observing circumstances for the evening of close approach with 1998 QE2 lying south of the celestial equator in the constellation of Libra. Over the next few days the asteroid does head north though, moving north of the celestial equator while in Ophiuchus.
On 31 May at 10pm (BST) it glows at mag. +10.7, within range of a small telescope, even allowing for extinction close to the horizon. It's probably best to wait for a while to allow skies to darken before attempting to observe it; it culminates close to 11pm just short of 18 degrees up from London, lying four degrees south of Zubenelgenubi (alpha Librae, mag. +2.7) at the precise position R.A. 14h 47.43m, Decl. -20o 25.2'. At this time its motion relative to the stellar background is 21.83 arcseconds per minute.
Try taking a five-minute exposure or subs with a CCD or DSLR on a guided, tracking mount to reveal the asteroid in the field. On the morning of 4 June it's much better placed in western Ophiuchus, close to epsilon Ophiuchi (mag. +3.2) at R.A. 16h 13.38m, Decl. -05o 32.2', over 30 degrees up at 11pm from London and culminating just after midnight. It's magnitude and motion is roughly the same.
As the month proceeds it moves into S.E Hercules and then into western Sagitta, dimming and slowing all the time but still at a very respectable magnitude +14.8 at the end of June, well within range of a big telescope or CCD on a moderate 'scope.