Update 2: JPL Small Body Database has been updated with radar data for 2010 AL30.
Update 1: Bernhard Haeusler (B82 Maidbronn, Germany) posted an animation of the NEO asteroid 2010 AL30, 100 x 2s. exposure, taken on January 13 between 01:01 and 01:16 GMT (~13MB).
Today, at 12:46 GMT, the asteroid with temporary designations 2010 AL30, discovered on January 10 by the Lincoln Near-Earth Asteroid Research (LINEAR) survey, flew by our planet at the distance of 0.000 86 AU (129,060 km; about 33% of the distance to the Moon). Within the next few hours, its brightness and elongation will drop dramatically and the object will disappear until the next (relatively) close approach in August 2028 (0.079 35 AU ~ 11.87 mil. km).
Thanks to photometric observations from around the world, pointing uncertainties have shrunk from about 523 arcseconds (3-sigma) to about 7 arcseconds. The new orbit calculations were accurate enough to point the radio telescopes of the Goldstone Observatory in Mojave Dessert at the asteroid. Early in the morning, between 02:20 and 04:20 GMT, astronomers were able to obtain valuable radar data which will dramatically improve the object’s orbit and provide additional information on its size and shape.
Lance Benner of NASA/JPL reported strong radar echoes from 2010 AL30 at Goldstone. The bandwidth was consistent with the asteroid’s expected size (10-20m). Bill Ryan and Richard Miles determined the rotation period to be roughly 9 minutes.
The image above displays 2010 AL30 taken by the SLOOH robotic observatory on the Canary Islands. The SLOOH space camera takes gray-scale image. To make a color image, the camera takes exposures with different filters. The individual filtered images are later combined into a single color image (just as the red, green and blue channels are combined to form a color picture). Because the asteroid was relatively close, long exposure left trails as the object moved relatively to background stars. Since different color filters were used at different times, in this case red was used first, then green and finally blue, the individual color trails do not overlap in the final image and reveal the tricolored line.
The two captures above are compositions of series of exposures Patrick Wiggins took with a C-14 @ f/5.5 telescope and SBIG ST-10 binned 3×3 using clear filter. The Field of View (FOV) is about 18′ x 26′. Note that in the second one the target is pretty faint (not surprising for 1″ exposures) so you have to look close to see it as it moves from left to right.
Click on the image above to see the apparent motion of 2010 AL30. Also, here is a composition of 200 images (~ 10MB).
Because of the unusual orbital period of 2010 AL30, which is almost precisely 1 year (366 days) some have suggested it could have been a man-made rocket stage in orbit about the Sun. Nevertheless, trajectory extrapolations show that the object cannot be associated with any recent launch and it has not made any close approaches to the Earth since well before the Space Age began (the last relatively close approach occurred at 08:09 GMT on August 17, 1947 when 2010 AL30 passed the Earth at the distance of 0.038 97 AU ~ 5.8 mil. km). Therefore, NASA’s Jet Propulsion Laboratory (JPL) Small Body Database has officially classified 2010 AL30 as a Near-Earth Object (NEO) of type Apollo (Near-Earth asteroids which cross the Earth’s orbit, similar to that of 1862 Apollo, i.e. with semi-major axis, a > 1.0 AU and perihelion distance, q < 1.017 AU).
In the end, the story of 2010 AL30 had a happy ending for inhabitants of the planet Earth; we’ve dodged yet another bullet. Even if 2010 AL30 had been on a collision course with our planet, it posed only a minimal risk as it would have certainly break up in Earth’s atmosphere. According to NASA/JPL one could expect a near-Earth asteroid of this size to pass within the moon’s distance about once every week on average.
For more 2010 AL30 images, fly-by animation and the apparent orbit sky chart see my earlier post.