BILLIONS of rogue planets in the Milky Way may outnumber stars!

Astronomer's have made a startling discovery that there are "hundreds of billions" of orphaned, Jupiter-sized planets in our galaxy. In fact, these free-floating orbs may outnumber the stars! From NYT:

There are two Jupiter-mass planets for each of the 200 billion stars in the Milky Way galaxy, according to measurements and calculations undertaken by an international group of astronomers led by Takahiro Sumi, of Osaka University in Japan, and reported in the journal Nature.

“It’s a bit of a surprise,” said David Bennett, a Notre Dame astronomer, who was part of the team. Before this research, it was thought that only about 10 or 20 percent of stars harbored Jupiter-mass planets. Now it seems as if the planets outnumber the stars.

I wonder if they also have moons like the gas giants in our neck of the woods. At least one of the scientists seems to postulate as much, From Nature:

Planetary scientist David Stevenson at the California Institute of Technology in Pasadena has considered how the temperatures on ejected planets might compare with those on star-bound bodies2. If Jupiter were kicked out of the Solar System, its surface temperature would drop by only about 15 kelvin, he says – although it would still be unsuitable for supporting life. However, "when you eject a planet that is quite massive, it could have carried along an orbiting body", Stevenson adds. "And that might be a more attractive possibility for life."

Unbound Earth-mass planets might still be capable of carrying liquid water, Stevenson says, even in the frozen reaches of interstellar space – as long as they have a heat-trapping hydrogen atmosphere. "That can bring the surface temperature up to 300 kelvin [about 27 °C]," he says. "And then you can have oceans."

What's your take on these newly discovered orphan worlds?

Learn more

• New York Times article 
• Nature.com article
• National Science Foundation details about the animation
• What is a rogue planet?
• NASA's PlanetQuest (exoplanet project)
• Exoplanets are the Future article on I09 (so much good stuff!)