Tholen has discovered a number of asteroids, including the lost, which may be an Apohele asteroid, and, which certainly is; in fact, it had the smallest semimajor axis and aphelion distance among the known asteroids. He won the H. C. Urey Prize in 1990. He co-discovered the asteroid99942 Apophis. 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. Later, then postdoc at University of Hawaii, Olivier R. Hainaut discovered that a nearly identical image was being discussed by late-night radio hostArt Bell and one of his guests, Courtney Brown, who claimed that it proved the existence of an unnatural object following the comet, something supposedly seen by those who had learned how to engage in the technique of "remote viewing". The image provided to Bell by Brown, and eventually made public on Bell's web site, did indeed show an object next to the comet that did not appear in archival images of the sky. In reality, that image had been digitally altered from the original image posted by Tholen, presumably by taking the image of a star near the edge of the frame, adding it next to the comet, and then trimming away the outer edges of the frame. Tholen and Hainaut exposed the fraud by producing the original image, which showed no such additional object. Nevertheless, some conspiracy theorists maintained that Brown's version was actually the original image and that Tholen had removed the additional object from the one on the Institute's web site. The Heaven's Gate cult was so convinced that the additional object was a spaceship coming to take them away from Earth that they committed mass suicide. The Mars-crosser asteroid 3255 Tholen, discovered by Edward Bowell in 1980, is named after David Tholen.
Personal interests
David Tholen and Roy Tucker, co-discovers of 99942 Apophis, are both fans of the TV series Stargate SG-1, which influenced the naming of the asteroid. The show's most persistent villain is "Apophis", an alien also named for the Egyptian god. "We considered a number of names, but 'Apophis' kept floating to the top," says Tucker. "Apophis was a very fitting name for not only because of its threatening nature, but also because of its evolution from an Aten asteroid to an Apollo asteroid during the 2029 encounter.". Tholen frequently posts to various Usenet groups using the alias . Tholen is a fan of the University of Kansas Jayhawkscollege basketball team and the Kansas City RoyalsMajor League Baseball team. He also plays clarinet and bass clarinet for the Honolulu Community Concert Band and the Oahu Community Orchestra. He is also a user of the OS/2, Linux, Windows, Solaris, and Mac OS operating systems.
