A team led by a University of Oklahoma astrophysicist discovered a rare and surprising new circumstellar disk: the oldest of its kind. They made this discovery working together with a remarkable team of collaborators with no formal training in astrophysics: citizen scientists from around the world.
In a paper that appeared in The Astrophysical Journal Letters, the authors describe a newly identified red dwarf star with a warm circumstellar disk of the kind associated with young planetary systems. Circumstellar disks around red “M” dwarfs like this one are rare to begin with. But this star, called AWI0005x3s, appears to have kept its disk for an exceptionally long time.
"Most disks of this kind fade away in less than 30 million years," says Steven Silverberg, a graduate student in the Homer L. Dodge Department of Physics and Astronomy at OU, and the lead author on the paper. "This particular red dwarf is a candidate member of the Carina association, which would make it around 45 million years old. It's the oldest red dwarf system with a disk we've seen in one of these associations."
The discovery relied on citizen scientists from Disk Detective, a project led by NASA/GSFC's Dr. Marc Kuchner, to find new circumstellar disks. At the project’s website, DiskDetective.org, users view ten-second videos of data from NASA’s Wide-field Infrared Survey Explorer mission (WISE), NASA’s Two-Micron All Sky Survey (2MASS) project, and other surveys. Since the launch of the website in January 2014, roughly 30,000 citizen scientists have participated in this process, performing roughly 2 million classifications of celestial objects.
"The WISE mission found 747 million objects, of which we expect a few thousand to be disks like this," Silverberg explains. "Without help from citizen scientists examining these objects and finding the good ones, we would have never spotted this object.”
Eight of these citizen scientists are featured by name as co-authors on the published paper.
“Unraveling the mysteries of our universe, while contributing to the advancement of astronomy, is, without a doubt, a dream come true,” says Hugo Durantini Luca, a citizen science co-author from Argentina, “especially while working alongside some of the best people from around the world.”
“I’ve loved astronomy since childhood and wanted to be part of the space program, as did every boy my age,” adds Milton Bosch, a citizen scientist co-author from California. “I feel very fortunate to be part of such a great group of dedicated people, and am thrilled to partake in this adventure of discovery and be a co-author on this paper.”
Determining the age of a star can be tricky or impossible. But the Carina association, where this star was found, is a group of stars whose motions through the Galaxy indicate that they were all born at roughly the same time in the same stellar nursery. Membership in one of these groups provides a reliable way to estimate the star's age. Knowing that this star and its disk are so old may help scientists understand why M dwarf disks appear to be so rare.
This star and its disk are interesting for another reason: the likelihood that it hosts extrasolar planets. Most of the extrasolar planets that have been imaged by telescopes so far dwell in disks similar to the one around AWI0005x3s. Moreover, this particular star is the same spectral type as Proxima Centauri, the Sun's nearest neighbor, which was shown to host at least one exoplanet in research published earlier this year.
Disk Detective is a collaboration between NASA, Zooniverse, the University of Oklahoma, University of Cordoba (Argentina), National Astronomical Observatory of Japan, Space Telescope Science Institute, Harvard-Smithsonian Center for Astrophysics, Carnegie Institution of Washington and Korea Astronomy and Space Science Institute. To join the search for more planetary habitats, go to http://www.diskdetective.org.