August 20, 2013
Not All Rogue Planets Are Born Within Solar Systems
Lee Rannals for redOrbit.com - Your Universe Online
A team of astronomers say free-floating planets can be born freely, outside of an existing solar system.
Previously, scientists believed free-floating planets, or "rogue planets," must have been ejected from existing planetary systems. However, telescopes at Chalmers University of Technology have helped astronomers discover not all of these rogue planets were created this way, but that some were born free.
Scientists believe there could be as many as 200 billion of these free-floating planets in our galaxy. In order to learn a little bit more about them, a team from Sweden and Finland observed the Rosette Nebula, which is a huge cloud of gas and dust 4,600 light-years from Earth in the constellation Monoceros (The Unicorn). They collected observations in radio waves with the 20-meter telescope at Onsala Space Observatory in Sweden.
”The Rosette Nebula is home to more than a hundred of these tiny clouds – we call them globulettes”, says Gösta Gahm, an astronomer at Stockholm University who led the project. “They are very small, each with 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."
Gahm said they have more reliable measurements of mass and density, as well as precise measurements of how fast they move relative to their environment.
“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," says team member Carina Persson, astronomer at Chalmers University of Technology.
The latest study shows tiny clouds within the Rosette Nebula are moving outwards at speeds of approaching 50,000 miles per hour.
”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," explains Minja Mäkelä, astronomer at the University of Helsinki.
There are countless numbers of nebulae like the Rosette within the Milky Way that have both birthed and faded away over the years. During the lifetime of these nebulae, the scientists believe they could have helped form many rogue planets.
“If these tiny, round clouds form planets and brown dwarfs, they must be shot out like bullets into the depths of the Milky Way”, says Gahm. “There are so many of them that they could be a significant source of the free-floating planets that have been discovered in recent years."
Last year, astronomers using the European Southern Observatory's Very Large Telescope (VLT) were able to identify a rogue planet sitting just 100 light-years away from Earth. The planet, CFBDSIR2149, was said to be part of a nearby stream of young stars, but with this new research it could mean the planet was actually born from clouds ejected from a nebula like the Rosette.