UW News

October 19, 2011

Spiral arms indicate possible planets in a star's gas-and-dust disk — with video

News and Information

A new image of a gas-and-dust disk around a sun-like star is the first astronomers have seen that displays structures that look like spiral arms, which could hint at the presence of still-unseen planets around the star some 456 light years from Earth.

Two spiral arms emerge from the gas-rich disk around SAO 206462, a young star in the constellation Lupus. This image, acquired by the Subaru Telescope and its HiCIAO instrument, is the first to show spiral arms in a circumstellar disk. The disk itself is some 14 billion miles across, or about twice the size of Pluto's orbit in our solar system.

The image comes from research that is part of the Strategic Exploration of Exoplanets and Disks with Subaru project, a five-year-long study in the near-infrared spectrum of young stars and their surrounding dust disks using the Subaru Telescope atop Mauna Kea in Hawaii. The work involves more than 100 scientists from 25 institutions, including John Wisniewski, a postdoctoral researcher in astronomy at the University of Washington.

“What we’re finding is that once these systems reach ages of a few million years, their disks begin to show a wealth of structure — rings, divots, gaps and now spiral features,” Wisniewski said. “Many of these structures could be caused by planets within the disks.”

The research is led by Carol Grady of Eureka Scientific Inc. in Oakland, Calif. She presented the image today at the Signposts of Planets meeting at NASA’s Goddard Space Flight Center in Greenbelt, Md.

The newly imaged disk surrounds SAO 206462, a star in the constellation Lupus. Astronomers estimate that the system is only about 9 million years old. The gas-rich disk spans some 14 billion miles, which is more than twice the size of Pluto’s orbit in our own solar system.

The Subaru image shows two spiral features arcing along an outer disk. Models indicate that a single embedded planet could produce a spiral arm on each side of a disk. The structures around SAO 206462 do not form a matched pair, suggesting the presence of two unseen worlds, one for each arm.

But processes unrelated to planet formation also could give rise to the spiral arms, and Wisniewski said the researchers will try to determine whether that is the case through further observation and theoretical modeling.

The work is supported by grants from the National Science Foundation and the Ministry of Education, Culture, Sports, Science and Technology-Japan.


Simulations of young stellar systems suggest that planets embedded in a circumstellar disk can produce many distinctive structures, including rings, gaps and spiral arms. This video compares computer simulations of hypothetical systems to the image of SAO 206462, produced by the the Strategic Exploration of Exoplanets and Disks with Subaru project that involves University of Washington astronomer John Wisniewski. (Credit: NASA’s Goddard Space Flight Center/NCSA)


For more information, contact Wisniewski at 206-427-0184 or wisniewski@astro.washington.edu.

NOTE: This information is taken from a news release from NASA Goddard Space Flight Center, which is available at http://www.nasa.gov/topics/universe/features/possible-planets.html.