A star discovered in Wesleyan’s Van Vleck Observatory could be vital to understanding how stars and planets are formed. Bill Herbst, Chair of the Astronomy Department and Director of the Van Vleck Observatory, has been leading research and observations on the star since he helped detect it in 1997.
The star, KH 15D, was first detected by Herbst and Kristin Kearns, who was then a graduate student at Wesleyan. Based on observations made mostly by undergraduate students in the observatory, they realized that the star’s light was being blocked out at certain intervals.
“It was winking at us,” Herbst said. “It was behaving unlike any star we’ve ever seen, almost like it was turning on and turning off.”
Through subsequent years of study directed in part by Catrina Hamilton, who earned her PhD in physics at Wesleyan, they discovered that KH15D is actually a binary star, which is a system of two stars that revolve around each other under their mutual gravitation. It faded out of sight about every 32 days and stayed faint for about 16 days.
“It’s orbiting another star, and they’re orbiting in very eccentric ellipses,” Herbst said. “As the star goes around in this orbit, one of the stars is popping up a surrounding disk. [The surrounding disk is] like a bagel, with the two stars in the middle. One of the stars pops up around the bagel, and [it’s as if] we’re looking at edge of that bagel. The bagel is actually precessing, which is like the wobbling motion that a top does when it starts to fall over.”
This precessing is increasingly obstructing astronomers’ view. As time goes on, the star’s cycle is slowly decreasing, and it is now visible for only 24 days, staying faint for 25 days. According to Herbst, within another 10 years it will not be visible at all.
“This particular situation has never been seen before,” Herbst said. “We now have a chance to study the bagel [the disk]; it’s a place where planets are forming, we think, with conditions similar to those that earth would have been under when it formed billions of years ago.”
The project has been supported in part by grants from organizations including Sigma Xi, the Mount Holyoke College Alumnae Association and the Perkin Fund. Herbst also received several grants from NASA’s Office of Space Science through its Origins of Solar Systems program (OSSP), which provides resources for planetary study. The most recent, announced March 15th by House Member for the third District of Connecticut Rosa DeLauro, was in the amount of $216,000.
“I have received NASA funding for probably about 12 years,” Herbst said. “When you get NASA funding you have to reapply, usually on a three-year basis; it’s always a challenge.”
Herbst has been working at Wesleyan since 1978. In that time he has received external grant support for various research projects totaling more than $1.1 million. Hamilton graduated last year and currently lectures at Mount Holyoke College.
Hamilton organized an international observing campaign during the fall, winter, and spring of 2001/2002. The goal was to continuously observe the star for as much time as possible.
Herbst and Hamilton are still collaborating with several international teams including the Maidanak Observatory in Uzbekistan and Max-Planck-Institute for Astronomy in Heidelberg, Germany. Nationally, they are using data from both the Hubble telescope and telescopes in the technological observatories in Hawaii. The project has also had a lot of undergraduate help from Wesleyan students in the past, but no students are working on the project currently.
“It just shows that even using a small telescope at Wesleyan, you can still make discoveries that are immensely relevant to the world,” Herbst said. “I’ll probably keep working on this until [the star] fades away in about 10 years[…]which happens to be about the time I retire.”