Jan. 7, 2014 Students in a University of Maryland undergraduate astronomy class have made a rare discovery that wowed professional astronomers: a previously unstudied asteroid is actually a pair of asteroids that orbit and regularly eclipse one another.

Fewer than 100 asteroids of this type have been identified in the main asteroid belt between Mars and Jupiter, said Melissa Hayes-Gehrke, who teaches the hands-on class for non-astronomy majors in which eight students made the find in the fall semester 2013.

The students' discovery that 3905 Doppler is an eclipsing binary asteroid will be presented in a poster session Jan. 7 at the 223rd meeting of the American Astronomical Society in National Harbor, Maryland and published in April in the Minor Planet Bulletin.

"This is a fantastic discovery," said University of Maryland Astronomy Prof. Drake Deming, who was not involved with the class. "A binary asteroid with such an unusual lightcurve is pretty rare. It provides an unprecedented opportunity to learn about the physical properties and orbital evolution of these objects."

"Actually contributing to the scientific community and seeing established scientists getting legitimately excited about our findings is a very good feeling," said Terence Basile, a junior from Beltsville, MD majoring in cell biology.

One of hundreds of thousands of pieces of cosmic debris in our solar system's main asteroid belt between Mars and Jupiter, 3905 Doppler was discovered in 1984, but over the coming decades it attracted scant attention. In September 2013 Hayes-Gehrke's students picked it and two other asteroids from an astronomy journal's list of asteroids worth observing because they were well positioned in the autumn sky and were scientific enigmas.

Student teams studying 3905 Doppler met over four nights in October 2013. Each four-person team observed and photographed the asteroid, using a privately owned telescope in Nerpio, Spain, which they accessed and controlled over the internet. Their main task was to photograph changes in the intensity of each asteroid's reflected light and turn those images into a lightcurve.

A lightcurve is a graph of a celestial object's brightness over time. Variations in brightness are often due to the object's shape, with spherical objects like planets yielding lightcurves that do not vary, and asymmetrical objects like asteroids producing peaks and valleys as the amount of reflected light varies. By measuring the time between maximum light intensities, planetologists can tell how fast an asteroid is rotating. Most asteroids complete a rotation in a few hours to a day.

"When we looked at the images we didn't realize we had anything special, because the brightness difference is not something you can see with your eyes," Hayes-Gehrke said. But when the two teams studying 3905 Doppler used a computer program to chart its lightcurve, they found the asteroid's light occasionally faded to nearly nothing.

"It was incredibly frustrating," said Alec Bartek, a senior physics major from Brookeville, MD. "For some reason our light curve didn't look right."

Excerpt from:

Rare eclipsing double asteroid discovered