M.P.E.C. 2012-Q72, issued on 2012 Aug. 28, reports the discovery of the PHA asteroid 2012 QG42 (discovery magnitude 16.8) by Catalina Sky Survey on images taken on August 26.3 with a 0.68-m Schmidt + CCD.

2012 QG42 has an estimated size of 200 m - 500 m (H=20.4) and it will have a close approach with Earth at about 7.43 LD (Lunar Distances) or 0.019 AU at 0510 UT on 14 Sept. 2012. This asteroid will reach an average magnitude of 13.6 around September 10-12. 2012 QG42 is a current radar target for ground based radio telescopes. Astronomers at Goldstone and Arecibo will try to observe it on September as "this object should be a really strong delay-Doppler imaging target".

It was classified as a PHA ((Potentially Hazardous Asteroid). PHA are asteroids larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.

We performed some follow-up measurements of this object, remotely from the Siding Spring-Faulkes Telescope South on 2012, September 04.5, through a 2.0-m f/10.0 Ritchey-Chretien + CCD. Below you can see our image, stack of 4x10-second exposures, taken with the asteroid at magnitude ~15.2 and moving at 4.35"/min. At the moment of the close approach on 14 September, 2012 QG42 will move at ~ 49"/min.
© Remanzacco Observatory
Here you can see a short animation showing the movement of 2012 QG42 (each frame is a 10-second exposure).