Disk surrounds planetlike object
Tiny planets may form in dusty disks around objects called planemos, much like they do around stars.
June 9, 2006
Disks of planet-forming material surround planemos — planetary-mass objects that drift through space instead of orbiting a star.
Ray Jayawardhana of the University of Toronto and Valentin Ivanov of the European Southern Observatory (ESO) in Chile observed infrared emission from dusty disks surrounding four planemos in star-forming regions about 450 light-years away. Jayawardhana presented the findings at a June 5 meeting of the American Astronomical Society (AAS) in Calgary, Canada.
The astronomers used ESO's 323-inch (8.2 meters) Very Large Telescope (VLT) and 138-inch (3.5m) New Technology Telescope to obtain optical spectra of six candidate planemos. They detected disks around four planemos; two with masses about 5-10 Jupiter-masses, and two about 10-15 times Jupiter's mass.
Another study confirms the scientists' findings. Jayawardhana and his colleagues also detected infrared emission from disks surrounding brown dwarf 2M1207 and its companion planemo 2MASS1207-3932B, abbreviated 2M1207B. Planemo 2M1207B is young (510 million years old) and lies about 170 light-years distant in the direction of Centaurus.
The 8-Jupiter-mass planemo, a gas giant, orbits the 25-Jupiter-mass brown dwarf — an object that lacks enough mass to support nuclear fusion; sometimes called a failed star — at a distance of 40 AU (1 AU is the average Earth-Sun distance). The scientists, who theorize the two likely formed together like a binary star system, made the observations using ESO's VLT.
"Now that we know of these planetary mass objects with their own little infant planetary systems, the definition of the word 'planet' has blurred even more," says Jayawardhana.