[BAA-ebulletin 00574] Asteroid 2011 GP59 makes a close approach

[Rick]

BAA electronic bulletin 00574: Asteroid 2011 GP59 makes a close approach
(c) 2011 British Astronomical Association    http://www.britastro.org/

This object was discovered on the night of April 8/9 by the Observatorio Astronomico de Mallorca (OAM) using a 0.45-m f/2.8 reflector at their La Sagra facilities (J75) in Andalusia, Spain (see http://www.minorplanets.org/OLS/ ).  The observers involved were S. Sanchez, J. Nomen, R. Stoss, M. Hurtado, J. A. Jaume and W. K. Y. Yeung.

2011 GP59 is due to make its closest approach to the Earth on April 15 at 19h UT at 1.39 lunar-distances but will be brightest at an average magnitude of 13.2 around 00h UT on the night of April 14/15 when it will be very favourably placed in the sky for observers worldwide.  This is the best NEO close approach these past few years and is bright enough to be observed visually in large (>0.2-m aperture) telescopes when on the night of Thursday 14th it will appear as a faint slow-moving star.

Observers should be aware however that the object, which is approximately 60 metres in diameter, appears to be rotating very quickly, once every 7.35 minutes in fact.  It is also quite oblong in shape such that its rotation makes it look distinctly bright then faint every 4 minutes or so. David Briggs observing with the Hampshire Astronomy Group's 0.4-m instrument on the evening of April 11 commented, "This is probably the fastest rotator I've seen so far in that it completely disappears from view every 3 to 4 images".

Brian Skiff of Lowell Observatory has completed a lightcurve analysis which can be found at ftp://ftp.lowell.edu/pub/bas/astlc/2011_GP59.png

Close inspection of Brian's results show that the object is almost certainly rotating around more than one axis, i.e. it is tumbling.

Weather for UK observers is likely to deteriorate over the coming days and so it might be best to observe tonight (Tuesday) around midnight or later when clear skies are forecast for much of England.  Unfortunately it will only be 16th magnitude at that time and so will be too faint to be picked up visually.  Positions can be found using the Minor Planet Center's ephemeris service at http://minorplanetcenter.net/iau/MPEph/MPEph.html

Clear skies,

Richard Miles
Director, Asteroids and Remote Planets Section
British Astronomical Association