[BAA-ebulletin 00574] Asteroid 2011 GP59 makes a close approach
BAA electronic bulletins service
baa-ebulletin at britastro.org
Tue Apr 12 11:31:48 BST 2011
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
rmiles at baa.u-net.com
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