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Free-floating planets may be born free; 200 billion starless planets roam Milky Way

Following analysis of new observations made by a team of Swedish and Finnish astronomers with telescopes from Chalmers University of Technology, the researchers discovered that tiny, dark, and round clouds in space are ideal incubators for planet formation.  The astronomers observed the Rosette Nebula, a gigantic cloud of dust and gas some 4,600 light years from earth in the Unicorn constellation, using the 20-meter telescope at Onsala Space Observatory in Sweden; APEX in Chile; and with the New Technology Telescope (NTT) at ESO’s La Silla Observatory in Chile.

In previous research endeavors, astronomers calculated that as many as 200 billion free-floating planets exist in the Milky Way galaxy.  Until now, astronomers believed that these types of planets – which do not have a parent star – resulted from ejection from an existing solar system.  Additionally, this new research into the tiny dark clouds reveals the possibility that a portion of the free-floating planets formed on their own.

According to Stockholm University astronomer Gösta Gahm, who led the project, “The Rosette Nebula is home to more than a hundred of these tiny clouds – we call them globulettes.  They are very small, each with diameter less than 50 times the distance between the Sun and Neptune,” he said. “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.”

According to team member Carina Persson, an astronomer at Chalmers University of Technology, “We found that the globulettes are very dense and compact, and many of them have very dense cores. That tells us that many of them will collapse under their own weight and form free-floating planets. The most massive of them can form so-called brown dwarfs.”

Minja Mäkelä, an astronomer at the University of Helsinki, explains that, “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. They have been accelerated out from the centre of the nebula thanks to pressure from radiation from the hot stars in its centre.”

The study, published in the article “Mass and motion of globulettes in the Rosette Nebula,” is found in the July issue of the journal Astronomy & Astrophysics.