UBC researchers find way of measuring surface gravity of faraway stars

Photo: Randy Shore

Randy Shore, Vancouver Sun writes, "Astronomers have developed a new tool in the search for habitable planets in other solar systems by measuring the surface gravity of stars too distant to study with conventional methods."

HED: How much would you weigh on another star? If stars had solid surfaces on which you could stand, then your weight would change from star to star. A 75-kg adult would tip the bathroom scale very differently in the surface gravities of three stars. On the Sun you’d weigh 20 times more than on Earth. On a red giant star you’d be 50 times lighter.
Photo: Vancouver Sun 

At least a dozen “Goldilocks” planets have already been identified, worlds that are neither too hot, nor too cold, but just right for liquid oceans and to support life as we understand it.

But deciding whether a planet is likely to support life depends on the properties of the star that it orbits. Knowing its surface gravity reveals its size, energy output and the size of the planets in its system.

Photo: Jaymie Mark Matthews

“The size of an exoplanet is measured relative to the size of its parent star,” said Jaymie Matthews, an astronomer at the University of British Columbia. “If you find a planet around a star that you think is Sun-like but is actually a giant, you may have fooled yourself into thinking you’ve found a habitable Earth-sized world.

Remember the fable The Boy Who Cried Wolf? No astronomer wants to be The Boy Who Cried Earth and later has to say ‘Never mind. My bad.’”

Scientists can use established methods to measure surface gravity of bright stars that are relatively close by, but that leaves out about a billion trillion stars and their planets.

“Whether we first find life on a planet 50 light years away or 5,000 light years away, the distance of the planet will be a footnote in the history books,” said Matthews. “The headline will be ‘We found life!’”
Matthews and study co-author Thomas Kallinger have found a way to use the subtle variations in the brightness of distant stars caused by convection and surface turbulence — like a boiling pot of soup — to calculate surface gravity...

The details of the autocorrelation time scale technique appear in the journal Science Advances.
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Additional resources  
Science Advances  01 Jan 2016:
Vol. 2, no. 1, e1500654
DOI: 10.1126/sciadv.1500654

Source: Vancouver Sun