David J. Tholen
David James Tholen (born 1955) is an American astronomer at the Institute for Astronomy of the University of Hawaii. He holds a 1984 PhD from the University of Arizona, and specializes in planetary and Solar System astronomy. He is a discoverer of minor planets and known for the Tholen spectral classification scheme used on asteroids.
Tholen has discovered a number of asteroids, including the lost 1998 DK36, which may be an Apohele asteroid, and 2004 XZ130, which certainly is; in fact, it had the smallest semimajor axis and aphelion distance among the known asteroids (and still holds both records among numbered asteroids as of March 2010). He won the H. C. Urey Prize in 1990.
He co-discovered the asteroid 99942 Apophis (previously known as 2004 MN4). This asteroid will closely approach Earth on April 13, 2029 and very briefly appear as bright as a third magnitude star.
In 1995, Tholen obtained images of the then newly discovered comet Hale-Bopp at a time when the comet was moving very slowly with respect to the background stars, thus permitting the red- green- and blue-filtered images to be combined into a color composite without the background stars appearing as separately colored dots. This color composite image was made publicly accessible via the Institute of Astronomy's web site.
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