Images: Recovery of Asteroid 128177 (2003 RA11)
Asteroid recovery: The story of the discovery of asteroid 128177 (2003 RA11) has already been told. This web page tells about its recovery (and the discovery of some other new asteroids). One of the powerful things about science is the ability to make predictions. Using the images of Asteroid 128177 taken in September 2003, it is possible to compute a tentative orbit and predict when would be the next time Earth is close to the asteroid and where to look to see it. Likewise, one can run the calculation backward to the previous time it was close to the Earth (to find out if it had been seen in old images but not been tracked). Successful recovery of an asteroid after so long is a dramatic demonstration of the laws of motion and gravity. And with each new observation, one can refine the details of the computed orbit, permitting predictions even further into the future. As a rule of thumb, if the asteroid can be spotted on four different close approaches (oppositions), the orbit is well enough determined that it will never be confused with other asteroids. At this point, the asteroid can receive a permanent minor planet number. ("2003 RA11" was the provisional designation assigned at discovery in 2003.) The permanent designation 128177 was assigned March 20, 2006. Upon having received a permanent designation, the discoverer may also suggest to the International Astronomical Union a proper name for the discovery.
The orbit of Asteroid 128177 (2003 RA11): The discovery images were taken on September 5 and 6, 2003. They were combined by the Minor Planet Center with isolated images taken by the NEAT telescope on Mount Palomar on August 22 and September 24, 2003, to make a preliminary orbit. This orbit was used to trace back prediscovery images from Mount Palomar in May of 2002. The two oppositions were combined to make an even better prediction for 2004. The movie loop above shows the successful recovery of the asteroid on the night of December 4, 2004. The asteroid was found to have both the position and motion predicted. (Find the starlike object near the bottom right corner drifting systematically down and to the right over the course of one hour. Ignore the random flashes caused by cosmic ray hits.) On January 5, 2006, we were able to observe the asteroid for a fourth consecutive opposition, and refine the orbit enough for a permanent designation. You can visualize the orbit of Asteroid 128177 with a NASA java applet.
The discovery of Asteroid 129099 (2004 XU3) et al.: The recovery images were each five minute, unfiltered exposures with our New Mexico telescope. In the discovery images from 2003 (taken with the Grand Rapids, Michigan telescope), the asteroid was only barely visible even when sets of three frames were averaged together. Notice by contrast how the asteroid is clearly seen in each frame of our new movie loop. This demonstrates the advantages of the New Mexico observing site, which has both darker and steadier skies.
The higher quality data also make it easier to discover more new asteroids! Look again at the movie loop above. In the upper left corner a second asteroid can be seen, looking and moving very much like Asteroid 128177 (you probably saw it already!). These images mark the discovery of this new asteroid, which received the provisional designation 2004 XU3, and later the permanent designation 129099. In the course of a month following up Asteroid 128177, a total of eight new asteroids were discovered! See our table of asteroid discoveries for details on each asteroid.