Tuesday, December 11, 2012

Close Approach of Asteroid 2012 XE54

M.P.E.C. 2012-X37, issued on 2012 Dec. 9, reports the discovery of the asteroid 2012 XE54 (discovery magnitude 17.3) by Catalina Sky Survey (mpc code 703) on images taken on December 09.1 with a 0.68-m Schmidt + CCD. 

2012 XE54 has an estimated size of 20 m - 44 m (based on the object's absolute magnitude H=25.6) and it will have a close approach with Earth at about 0.6 LD (Lunar Distances = ~384,000 kilometers) or 0.0015 AU (1 AU = ~150 million kilometers) at 1004 UT on Dec. 11 2012. This asteroid will reach the peak magnitude ~13.0 on December 11 around 0600 UT.

We performed some follow-up measurements of this object, from the H06 ITelescope network (near Mayhill, NM) on  2012, Dec. 11.3, through a 0.25-m f/3.4 reflector + CCD. Below you can see our image, single 60-second exposure, taken with the asteroid at magnitude ~13.2 and moving at ~630 "/min. The asteroid is trailed in the image due to its fast speed. At the moment of the close approach 2012 XE54 will move at ~ 720"/min. Click on the image below to see a bigger version. North is up, East is to the left.

Below you can see a short animation showing the movement of 2012 XE54 (three consecutive 60-second exposures). North is up, East is to the left. Click on the thumbnail for a bigger version:

According to calculations made on December 10 by P. Tricarico, 2012 XE54 "will likely cross the Earth's shadow, causing a partial eclipse of the asteroid a few hours before reaching its minimum distance with the Earth. Asteroids eclipsing during an Earth flyby are relatively rare, with the first known case of asteroid 2008 TC3 which was totally eclipsed just one hour before entering Earth's atmosphere over Sudan in 2008, and asteroid 2012 KT42 experiencing both an eclipse and a transit during the same Earth flyby in 2012".

The plot below shows the expected average apparent magnitude of asteroid 2012 XE54 (line), the filter-corrected magnitudes reported (blue boxes) and the dip due to the eclipse (red curve).

Credit: Pasquale Tricarico, 2012

This prediction has been confirmed by observations made by Peter Birtwhistle (J95 mpc code). Peter put up a very preliminary lightcurve (see graph below) covering the eclipse earlier today, showing minimum centred around approx. 01:37:00 UT, probably around mag ~ +17.5.

Credit: Peter Birtwhistle, 2012

by Ernesto Guido & Nick Howes in memory of our dear friend & colleague Giovanni Sostero

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