Rogue planets believed to roam the galaxy with no star

Astrophysicists Louis Strigari from Stanford University's Kavli Institute and some colleagues believe that the Milky Way galaxy could be the home to as many as 100,000 planets that roam freely rather than orbiting stars. That number could be off though, it was arrived at by extrapolating from observations of 12 nomad planets.

This 12 pack of nomad planets was discovered using a something called gravitational microlensing. This is where the gravity of the planet would briefly contort the light from a star as it passes in front. The scientists factored in the gravitational pull the Milky Way, how much material it contains, and how the material can be divided up among planetary bodies from massive objects the size of gas giants down to tiny bodies like Pluto. One of the more interesting findings the researchers came up with is that they don't believe there are enough solar systems in the galaxy to account for all of nomad planets roaming the Milky Way.

In other word's, all the nomad planets couldn't have been ejected from a solar system by the host stars gravity. That raises questions about previously held notions of how planets form and raises an interesting prospect concerning the possibility for habitable planets. The team thinks that some of these nomad planets could possibly be large enough to have thick atmospheres with the potential to capture heat for life such as bacteria.

"If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist," said Strigari.

[via Discovery]