Free-Floating, Rogue Planets Born from Tiny, Cold Clouds

Free-floating planets are some of the most curious bodies in the universe. They travel through space without need of a parent star, hurtling past other planetary bodies. Now, astronomers have discovered that these planets may not have even needed to start with a parent star. It turns out that tiny, round, cold clouds in space have all of the right characteristics to form planets.

There may be as many as 200 billion free-floating planets in the Milky Way galaxy. Until now, though, scientists believed that these "rogue planets" must have been ejected from planetary systems. Yet it turns out that this isn't necessarily the case. Tiny dark clouds in space could potentially indicate that some of these planets formed on their own.

Spotting these clouds of gas wasn't easy, though. The astronomers used several telescopes to observe the Rosette Nebula, a huge cloud of dust and gas located about 4,600 light-years from Earth in the constellation Monoceros. After examining the radio wave data, they found evidence of tiny clouds within the nebula.

"The Rosette Nebula is home to more than a hundred of these tiny clouds--we call them globulettes," said Gosta Gahm, an astronomer at Stockholm University, in a news release. "They are very small, each with a 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."

So what did they find out about these clouds of gas? It turns out the globulettes are very compact with very dense cores. It's very likely that these clouds of gas will collapse under their own weight in the future and, eventually, form free-floating planets. The more massive clouds of gas, though, are likely to form brown dwarfs, which are dim stars.

"We think that these small, round clouds have broken off from tall, dusty pillars of gas which were sculpted by the intense radiation from young stars," said Minja Makela, one of the researchers, in a news release. "They have been accelerated out from the center of the nebula thanks to pressure from radiation from the hot starts in its center."

Over time, these clouds are being thrown out of the Rosette Nebula. Since many other nebulae probably possessed similar globulettes, they could be a significant source of free-floating planets in our universe. Currently, researchers are investigating a bit further, finding out more about how these rogue planets form.

The findings are published in the journal Astronomy & Astrophysics.