Star Cluster Could Help Astronomers Find Earth-Like Planets
June 23, 2012

Star Cluster Could Help Astronomers Find Earth-Like Planets

A loose star cluster located approximately 800 to 1,000 light years from Earth, detected by scientists more than 180 years ago but never analyzed in detail, could be vital in helping experts not only to understand how stars like the Sun evolve, but also to help them in the search for Earth-like planets.

According to a June 22 press release, researchers from Penn State University and colleagues from the University of California, Santa Cruz (UCSC); Yale University; and the California Institute of Technology (CalTech) has demonstrated that the cluster, Ruprecht 147 (also known as NGC 6774), is slightly younger than our Sun and close enough to Earth to be observed using binoculars under certain conditions.

While searching for planets that have Earth-like mass and an orbit that allows liquid surface water to exist, astronomers tend to seek out stars that have the mass the same size as the Sun or smaller, the researchers said. The Ruprecht 147 cluster is much larger on the sky than most objects that the astronomers study, the team needed to use specialized wide-field cameras in order to get all of the cluster's stars within a single frame of view.

"We have discovered that a previously unappreciated open star cluster, which is a little younger than our Sun, holds great promise for use as a standard gauge in fundamental stellar astrophysics," Jason T. Wright, an assistant professor of astronomy and astrophysics at Penn State who initially proposed the concept for the research, said in a statement. "The Ruprecht 147 cluster is very unusual and very important astrophysically because it is close to Earth and its stars are closer to the Sun's age than those in all the other nearby clusters."

"For the first time, we now have a useful laboratory in which to search for and study bright stars that are of similar mass and also of similar age as the Sun. When we discover planets around Sun-like and lower-mass stars, we will be able to interpret how old those stars are by comparing them to the stars in this cluster," he added. "All of the other nearby clusters astronomers study contain stars much younger than the Sun, and all of the older stars are more than 3,000 light years away. So this cluster, being both old and close, provides a unique opportunity."

Ruprecht 147 was first discovered by British astronomer John Herschel in 1830, but Wright and his colleagues have for the first time found that the cluster is only a little bit younger than the Sun in terms of the astronomical time scale. They report that NGC 6774 is approximately 2.5 billion years old, making it approximately half of the age of the star our planet orbits, and about the same size the Sun was when multicellular life originally emerged on Earth.

Wright and co-authors Jason Curtis of Penn State; Angie Wolfgang of USCS, John Brewer of Yale, and John Asher Johnson of Cal Tech, have submitted a paper detailing their discovery to the Astronomical Journal. In addition, Curtis will present their findings later on this month in the 17th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun in Barcelona, Spain.

"Our project with this important cluster is just beginning," Wright said "Eventually, it is going to let us find and study nearby stars with a mass like the Sun's, to help in the hunt for Earth-like planets, and to test and improve the models astronomers use to understand the evolution of stars including our own Sun."