Astronomers Say Planets Can Form Without Parent Stars

Posted on August 21, 2013

Rosette Nebula globulettes

Astronomers estimate there may be as many as 200 billion free-floating planets in the Milky Way. Some of these free-floating planets or "rogue planets" are nomad planets that may have been booted out of the star systems in which they formed. The rest of them could be planets that formed without the help of a star. Astronomers from the Chalmers University of Technology in Sweden say in a release that new observations of tiny dark clouds in space suggest some free-floating planets formed on their own, without stars.

Gösta Gahm, astronomer at Stockholm University, who led the project, says, "The Rosette Nebula is home to more than a hundred of these tiny clouds – we call them globulettes. They are very small, each with diameter less than 50 times the distance between the Sun and Neptune. Previously we were able to estimate that most of them are of planetary mass, less than 13 times Jupiter's mass. Now we have much more reliable measures of mass and density for a large number of these objects, and we have also precisely measured how fast they are moving relative to their environment."

Carina Persson, astronomer at Chalmers University of Technology, says, "We found that the globulettes are very dense and compact, and many of them have very dense cores. That tells us that many of them will collapse under their own weight and form free-floating planets. The most massive of them can form so-called brown dwarfs."

The research was published here in Astronomy & Astrophysics.

Photo: ESO/M. Mäkelä