A group of researchers have discovered a new class of planets in the Milky Way Galaxy and they don't have an orbital home.
According to a study done by a group of international researchers, the planets are dark, isolated Jupiter-mass bodies located far away from any host star. The researchers, led by Takahiro Sumi of Osaka University, say the planets were most likely ejected from developing planetary systems. The researchers' study will appear as part of a paper appearing in the May 19th issue of the journal Nature.
An analysis of the central bulge of the Milky Way galaxy a few years back by a joint Japan-New Zealand survey revealed the planets, 10 in all. University of Notre Dame Astronomer David Bennett, who co-authored the study with Sumi, says the planets confirm the existence of free-floating planets and explain how they came to be.
Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth by close encounters with other planets, Bennett said.
The researchers say the fact there were 10 free-floating planets discovered, likely means there are many more out there. Free-floating planets are hard to detect without a host star. However, there are likely twice as many free-floating Jupiter-mass planets as stars. They may even be as common as planets, like Earth, that orbit stars.
Our survey is like a population census. We sampled a portion of the galaxy and, based on these data, can estimate overall numbers in the galaxy, Bennett said. The survey is not sensitive to planets less massive than Jupiter and Saturn, but theories suggest that lower-mass planets like Earth should be ejected from their stars more often and are thus more common that free-floating Jupiters.
If there were a free-floating planet with the same mass as the Earth, scientists say there might even be life on said planet. This would be as a result of the greenhouse effect of a large amount of Hydrogen in their atmospheres.
In order to make the discovery, the scientists used a method called microlensing. The method, which uses a special 1.8-meter (5.9-foot) telescope, takes advantage of the fact that light is bent as the rays pass close to a massive object, like a star. The gravity of the mass of the foreground planet warps surrounding space and acts like a giant magnifying glass. As long as there is perfect alignment, the outcome is a brightening of the source star.
The researchers aren't completely positive that the planets are free-floating. There is a possibility the planets may be in very distant orbits. However, Bennett says, that is unlikely.
If free-floating planets formed like stars, then we would have expected to see only one or two of them in our survey instead of 10, Bennett said.