Missing planets proof of destructive power of stars’ tides

April 28th, 2009 - 2:31 pm ICT by ANI  

Washington, April 28 (ANI): Astronomers have come across first time evidence of the destructive power of stars’ tides, in the form of missing planets outside our solar system.

According to University of Washington astronomer Rory Barnes, the idea that gravitational forces might pull a planet into its parent star has been predicted by computer models only in the last year or so, and this is the first evidence that such planet destruction has already occurred.

“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.

“Tides distort the shape of a star. The bigger the tidal distortion, the more quickly the tide will pull the planet in,” Jackson said.

According to Jackson, the destruction is slow but inevitable.

“The orbits of these tidally evolving planets change very slowly, over timescales of tens of millions of years,” Jackson said.

“Eventually, the planet’s orbit brings it close enough to the star that the star’s gravity begins tearing the planet apart,” he added.

“So, either the planet will be torn apart before it ever reaches the surface of the star, or in the process of being torn apart, its orbit eventually will intersect the star’s atmosphere and the heat from the star will obliterate the planet,” he further added.

Jackson hopes new observations will provide new lines of evidence to investigate how a star’s tides can destroy planets.

“For example, the rotation rates of stars tend to drop, so older stars tend to spin more slowly than younger stars,” he said.

“However, if a star has recently consumed a planet, the addition of the planet’s orbital angular momentum will cause the star to rapidly increase its spin rate. So, we would like to look for stars that are spinning too fast for their age,” he added. (ANI)

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