Click on the image for a full-sized version. Thanks to Joe Pow!
The RIT Observatory

Figure A.50 taken from Hanus et al., arXiv:1702.01996

The picture above shows a model of the asteroid (10) Hygiea, seen at two orientations. The asteroid is about 410 km in diameter, too small to measure precisely even with the largest telescopes.

But every now and then, this asteroid (like others) passes in front of a bright star, casting a thin shadow across the Earth. Astronomers living underneath the shadow can measure the time during which the star's light is blocked, yielding an estimate of the asteroid's size along one thin slice. The red lines in the images above show these slices, observed by 5 or 6 astronomers (mostly amateurs) across the world. Our telescopes at RIT contributed one of these slices, during an occultation on September 6/7, 2002.

You can read the full story on this research, which combines ground-based occultation measurements with images taken by the giant Keck Telescope, at

Volumes and bulk densities of forty asteroids from ADAM shape modeling by Hanus et al., arXiv 1702.01996.

The interim Director of the RIT Observatory during academic year 2016-2017
Last modified 2/8/2017 by MWR