From Seattle, at a meeting of the American Astronomical Society
Material shed by a dying star might give birth to planets. The red dwarf star Mira A, located 350 light-years from Earth, is famous for its wildly varying brightness, which changes by a factor of 1,000 during every 11-month cycle. The elderly star blows off about an Earth-mass of its dusty outer layers every 7 years. About 1 percent of that material is snatched by the star’s close companion, Mira B.
New near-infrared images indicate that the material—silicate dust similar in composition to Earth’s mantle—has formed a disk around Mira B. Observations with two large telescopes, the Keck 1 on Hawaii’s Mauna Kea and the Gemini South atop Cerro Pachon in Chile, reveal that the disk resides at about the same distance from Mira B as Saturn does from the sun, reports Michael Ireland of the California Institute of Technology in Pasadena.
Although the disk is now about as massive as Jupiter, it’s likely to become three to five times as heavy during the next million years, as Mira A sheds more of its mass and becomes a dead cinder called a white dwarf. Gas and dust coalescing in a disk that heavy have the potential to make planets, Ireland says.
The discovery, says Ireland, suggests that while some stars may be born with planet-making disks, others may acquire them from partners. He adds that the finding also opens new venues to searches for young planets: double-star systems that contain white dwarfs. Such systems are expected to be relatively common where stellar death exceeds star birth, he notes, such as in our region of the galaxy.