Last updated 22 Apr 2017

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2003 SQ222 (extremely small Apollo making close approach to Earth)

Only 4-8 metres in diameter, 2003 SQ222 passed just 0.23 Lunar distances (0.00059 AU) from the Earth and 11 hours later was discovered on images taken at the Lowell Observatory for the LONEOS survey. Ted Bowell notes in the MPML that it may be "the smallest object for which we have a reasonably good orbit". 

The images here were taken about 16 hours after discovery, while the object was still on the NEO Confirmation page. It was listed as being mag +20.1-20.2 and moving at about 10"/min. Exposures were limited to 16 seconds each to freeze the motion of the object to approximately the pixel size of the camera (3"/pixel, operating in 2x2 binned mode) and a total of 90 exposures were taken.

The object was not identified in the images taken at Great Shefford that night, but was readily apparent when re-examined later. The positions along with a later set from LONEOS were published in MPEC 2003-T03.

An enlargement of the animation above is shown here and covers an area of  4'45" x 1'39"

An unusual aspect of this object was that it decelerated noticeably in the 52 minutes it was being observed. Stacking all 90 frames using the average motion during the 52 minutes causes the resultant image to be elongated instead of circular. The stack below is of all 90 frames and enlarged by a factor of 4 from the original.

By chance, another asteroid was very close to 2003 SQ222 during the time the images above were being taken. 2003 SC49 is a main belt object and had been discovered at Palomar on 18 Sep 2003 and had been observed by LONEOS just a week before discovering 2003 SQ222.

Three sets of five frames (from the 90 taken for 2003 SQ222) were stacked and used to show 2003 SC49, the field is the same as the field in the animations above:

2003 SC49 in same field as 2003 SQ222

Some links to other archived articles on 2003 SQ222:

That Was Close! (
Asteroid Whizzes Very Close By Earth (Lowell Observatory)
Discovery of 2003 SQ222 (Lowell Observatory)
Closest Asteroid Yet Flies Past Earth (New Scientist)
A Tiny Asteroid Whizzes By (Sky & Telescope)
Small Asteroid Came Very Close (Universe Today)


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