A new study suggests that planets that wander through space rather than orbit around a star – known as “nomad planets” – are surprisingly common, Space.com reported.
Researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of Stanford University and the SLAC National Accelerator Laboratory, estimate that there are 100,000 times more of these planets than stars in the Milky Way. The study was published in the Monthly Notices of Britain’s Royal Astronomical Society on Thursday.
The researchers said that these free-floating planets may have been ejected from their original parent stars and could be accompanied by flocks of moons, the San Francisco Chronicle reported.
"An interstellar object might seem an especially inhospitable habitat," the scientists wrote in their report, according to the San Francisco Chronicle. However, they said, it’s possible the planets could have warm climates, heated by internal radioactivity, and thick atmospheres, meaning they could harbor life.
According to Space.com:
If the estimated number of these nomad planets is correct, the results could lead to exciting prospects about the origin and abundance of life in our Milky Way galaxy. For instance, as these homeless planets mosey through space, collisions could break apart pieces of these rogue worlds and fling bacterial life onto other celestial bodies, the researchers said.
Almost all of the 700 planets discovered outside our solar system orbit stars, but last year, scientists spotted about a dozen planets with no discernible star, Space.com reported.
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Confirming that nomad planets exist will take at least a decade, the San Francisco Chronicle reported, but scientists are hopeful that next-generation telescopes coming on line will help with the task. The space-based Wide Field Infrared Survey Telescope and the Earth-based Large Synoptic Survey Telescope are scheduled to start peering into space in the early 2020s.
While nomad planets may be numerous, scientists don’t think they threaten Earth. "There are lot of other things I'd be worried about before a free-floating planet collides with Earth," Eric Ford, a University of Florida astrophysicist who was not involved in the study, told National Geographic. "A good old-fashioned comet or asteroid wiping us out is something I'd be much more worried about."