Sunday, February 26, 2012

‘Nomad planets’ may fill the Milky Way

Planets spit out by suns that have migrated out of solar systems over hundreds, thousands, millions or billions of years, mingle with new, freshly spit out planets that suns routinely eject during solar storms into the vastness of space, and from exploding stars at the end of their cycle. Some globs of matter are remnants of the placenta of baby stars spawned from the center of galaxies. And then there is that other side of things that come from the mystery zone where other kinds of souls play games and hide where suns don't shine.


Nomad planets” may fill the Milky Way, according to a new study by researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). “Nomad planets” are special because they do not orbit a star like Earth, but wander through space without a home. There may be as many as 100,000 times more “nomad planets” in the Milky Way than there are stars.

The researchers who conducted the study believe that the observation of “nomad planets” will probably impact how planet formation is understood. “If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” said Louis Strigari, the leader of the research team. “Nomad planets” may create enough heat through internal radioactive decay and tectonic activity to support bacterial life.

Although the discovery of planets that orbit stars is nothing new to the scientific community (500 planets outside our solar system have been found over the past 20 years), the unearthing of more “nomad planets” is still a cause for celebration. A Stanford Universitypress release reveals that astronomers found approximately 12 “nomad planets” in 2011.

In 2011, TIME reported on the discovery of 10 rogue planets (another term for “nomad planets”). In the article, TIME said that “nomad planets” might have become homeless after extremely close gravitational encounters with other planets.

In order to detect the existence of “nomad planets” in the Milky Way, scientists utilized a technique called gravitational microlensing. The technique allows scientists to identify a planet by watching for the brief refocusing of a star’s light, which is caused by the gravity of passing planets.

The KIPAC team found that “nomad planets” are extremely common by considering various pieces of evidence, facts and theories. The researchers factored in the known gravitational pull of the Milky Way, the amount of matter available to form “nomad planets” and theories on how “nomad planets” might form.

“To paraphrase Dorothy from The Wizard of Oz, if correct, this extrapolation implies that we are not in Kansas anymore, and in fact we never were in Kansas,” said Alan Boss of the Carnegie Institution for Science in Washington, D.C., who wrote The Crowded Universe: The Search for Living Planets and was not involved in the study. “The universe is riddled with unseen planetary-mass objects that we are just now able to detect,” Mr. Boss added.

At this point scientists cannot provide a more accurate estimate of the number of “nomad planets” in the Milky Way because they lack the necessary technology.

“Few areas of science have excited as much popular and professional interest in recent times as the prevalence of life in the universe,” said the study’s co-author and KIPAC Director Roger Blandford. “What is wonderful is that we can now start to address this question quantitatively by seeking more of these erstwhile planets and asteroids wandering through interstellar space, and then speculate about hitchhiking bugs,” Mr. Blandford added.

Eric Ford, a University of Florida astrophysicist who did not take part in the study, had his curiosity sparked by the results. “The art form here is what size clusters do most stars form in, and how are the clusters structured? There’s a crucial element of timing here,” said Mr. Ford, according to National Geographic.

Although some may interpret this study as evidence that “nomad planets” could be a threat to Earth, Mr. Ford said that a mid-space collision is highly unlikely. “Instead of thinking these planets are oddballs, we now think they’re common,” posited Mr. Ford. “There are lot of other things I’d be worried about before a free-floating planet collides with Earth,” said the astrophysicist, adding that “a good old-fashioned comet or asteroid wiping us out is something I’d be much more worried about.”

KIPAC says its mission is to “bridge theoretical and experimental physics communities, and bring their combined strengths to bear on some of the most challenging and fascinating problems in particle astrophysics and cosmology.” KIPAC is a joint institute of Stanford University and the Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory.

The results of the study were published in a paper submitted to the Monthly Notices of the Royal Astronomical Society.

Read more: