ASTEROID CERES ORBITS PAST GALAXY NGC 4746


Ceres was the first asteroid discovered long ago in 1801. Although it is the largest asteroid, it is only about the diameter of Earth’s Moon. Ceres orbits between Mars and Jupiter, and takes 4.7 years to complete one circuit around the Sun.

On the evening of February 25, 2000 Ceres passed near the 13th magnitude edge-on galaxy NGC 4746 in the constellation Virgo. Sophomore physics major, Trisha Youngquist, and I attempted to record Ceres’ orbital motion by making a series of red-filtered CCD images, one every 30 minutes for as long as possible. The first image was taken at 10:00 PM. The sky remained clear for the first 4 images. Then clouds and haze increased. We tried to compensate by increasing exposure times, but clouds eventually covered the whole sky. We gave up at 2:00 AM after recording 9 images.

Trisha and I then processed the images and assembled them into a "movie" showing about 4 hours of orbital motion. There are 9 frames in the animation below. The exposure times for these frames are 60, 60, 60, 60, 180, 120, 240, 240, and 240 seconds, respectively. Galaxy NGC 4746 can be seen as an elongated object near center. The galaxy and nearby stars fade in and out during the animation because clouds passed by during some of the exposures. Ceres is overexposed, and the galaxy is underexposed.

We hoped to try again and make a better, longer movie on one of several nights when Ceres passed by other galaxies. Every one of these opportunities was clouded out! Virginia weather is often frustrating!



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