Mystery of the Missing Virtual Planets

During the last two decades, astronomers have found hundreds of planets orbiting stars outside our solar system. New research indicates they might have found even more except for one thing – gravitational forces have pulled a planet into its parent star, said astronomer Rory Barnes of the University of Washington Virtual Planet Laboratory.

The Virtual Planet Laboratory (VPL) is a team of scientists who are building computer simulated Earth-sized planets to look for habitable planets around other stars by allowing them to distinguish between planets with and without life. These simulated environments visualize what these planets look like from space to help future missions recognize signs of possible life in the spectra of planetary atmospheres and surfaces. VPL findings will directly influence the development of future space missions designed to

"When we look at the observed properties of extrasolar planets, we can see that this has already happened – some extrasolar planets have already fallen into their stars," he said.

Computer models can show where planets should line up in a particular star system, but direct observations show that some systems are missing planets close to the stars where models say they should be.

The research involves planets that are close to their parent stars. Such planets can be detected relatively easily by changes in brightness as their orbits pass in front of the stars.

But because they are so close to each other, the planet and star begin pulling on each other with increasingly strong gravitational force, misshaping the star's surface with rising tides from its gaseous surface.

Most of the planets discovered outside of our solar system are gas giants like Jupiter except that they are much more massive. However, earlier this year astronomers detected an extrasolar planet called CoRoT-7 B that, while significantly larger than our planet, is more like Earth than any other extrasolar planet found so far.

However, that planet orbits only about 1.5 million miles from its star, much closer than Mercury is to our sun, a distance that puts it in the category of a planet that will fall into its star. Its surface temperature is around 2,500 degrees Fahrenheit "so it's not a pleasant environment," Barnes said, and in a short time cosmically – a billion years or so – CoRoT-7 B will be consumed

Orbits of these tidally evolving planets change very slowly, over timescales of tens of millions of years, Eventually the planet's orbit brings it close enough to the star that the star's gravity begins tearing the planet apart.

The scientists say their research will have to be updated as more extrasolar planets are discovered. NASA, which funded the research, recently launched the Kepler telescope, which is designed specifically to look for extrasolar planets that are closer in size to Earth.

The source paper is available at http://lanl.arxiv.org/abs/0904.1170

Posted by Jason McManus.