2011 GP59 - Close Approach

The Mpec circular 2011-G60 issued on April 09, 2011 announced the discovery of a new Aten asteroid officially designated 2011 GP59. This asteroid (~ magnitude 17.5) was discovered by La Sagra Survey through their 0.45-m f/2.8 reflector + CCD, on images obtained on April 08.9, 2011. After posting on the Minor Planet Center's 'NEOCP' webpage, other CCD astrometrists have been able to follow-up the new object to define its orbit.

According to the preliminay orbit, 2011 GP59 is an Aten type asteroid. This class of asteroids are defined by having semi-major axes of less than one astronomical unit (the distance from the Earth to the Sun). 2011 GP59 will have a close approach with Earth on April 15, 2011 at 1909 UTC at rougly 0.003567AU or 1.39 LD (Lunar Distance) reaching the magnitude ~13. Its absolute magnitude H=24.30 correspond to an approximate diameter of 50 meters.

2011 GP59 shows evident magnitude fluctuations. Below you can see a light-curve made by Brian Skiff (Lowell Observatory): 6-hours of observations using the Lowell 0.55-m Schmidt with 45-second exposures showing an amplitude in excess of 2 full magnitudes over a period of roughly 7.5 minutes.

(Credit: Brian Skiff - Lowell Observatory)

We have been able to follow 2011 GP59 on April 12.35 remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD. Below you can see an animation showing the fast movement (the object was moving at 10.5 "/min) of 2011 GP59 on the sky on April 12, 2011. Each frame is a stack of 2x20-second exposure. The asteroid is moving from the top left corner to the bottom right corner. In the animation you can easily see the rapid brightness fluctuations of this object.

Click on the thumbnail below to see the animation:

UPDATE - April 14, 2011 - 13:30UT

We imaged 2011 GP59 on April 14.36, 2011 remotely from the GRAS Observatory (near Mayhill, NM) through a 0.51-m, f/6.9 reflector + CCD.

It's a single unfiltered exposure of 600 seconds, showing 2011 GP59 as trail with brightness fluctuations clearly evident (click on the image for a bigger version) :



by Ernesto Guido & Giovanni Sostero