Saturday, June 16, 2012

OT: Near Earth Asteroid 2012 LZ1 fly-by imaged, June 15

On June 10, 2012, Australian Siding Spring astronomer Rob McNaught and colleagues discovered a bright Near Earth Asteroid (NEA). It got the provisional designation 2012 LZ1 and turned out to be large: it is estimated to be about 500 meter in diameter (UPDATE 22 June 2012: radar observations from Arecibo obtained during the fly-by actually showed it to be twice as large, i.e. 1 km diameter! This suggests a low albedo, which might imply a carbonaceous composition). It made it's closest approach to the earth/moon system around midnight of June 14/15. With a pass distance of 5.3 million km (a multitude of the Earth-Moon distance), this flyby was not particularly close. But because the asteroid is large, it became quite bright, ~ mag. +13.

In the early morning of June 15, some 9 hours after closest approach, I used the "remote" 37-cm F/14 Cassegrain of UoI Rigel observatory at Sonoita, Arizona, USA (MPC 857, the same telescope that I often use to image geostationary satellites)  to image the asteroid (I also obtained some imagery using the larger 61-cm telescope of Sierra Stars Observatory in California).

click image to enlarge

The image above is a stack of 4 CCD images, each of 30 second exposure and spaced 5 minutes in time, obtained with the Rigel telescope. The asteroid can be seen as a set of 4 short trails lining up. It was moving at a rate of about 35"/minute near the Aquila-Capricorn border at that time and was near mag. +13.

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