A new study suggests that the Milky Way galaxy may harbor a huge number of rogue planets that were kicked out of the star systems where they were born.
The wandering planets, which are rambling through space instead of being locked in orbit around a star, are much more common than predicted, say researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of Stanford University and the SLAC National Accelerator Laboratory.
Researchers claim that there may be 100,000 times more of these nomad planets than stars in the Milky Way.
"If any of these homeless planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist," said study leader Louis Strigari.
To find out the identity if these free-floating planets, two astrophysicists simulated the evolution of several sizes and densities of star clusters.
The simulations indicated that between 3 and 6 percent of stars host rogue planets, a much higher number than previously estimated.
According to initial estimates, astronomers considered two free-flying planets for every normal star in the galaxy, but the new study revealed that nomad planets might be up to 50,000 times more than what thought before.
Characteristics of these foreign objects are still unknown; they could be icy bodies, similar to other objects found in the outer solar system, rocky like asteroids, or gas giants similar to the most massive planets in our solar system.
Researchers used a technique called gravitational microlensing to detect these homeless planets. The method examines the effects of a massive object passing in front of a star.
Almost all newfound worlds orbit stars, but scientists discovered about a dozen planets last year which had no discernible host star.