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Speaking of Science

A new way of calculating distant stars' gravity could help us find alien worlds

By Rachel Feltman

January 4, 2016 at 8:31 AM

The key to finding Earth-like worlds is learning all about their host stars. (NASA)

Researchers believe they've come up with a new, more accurate method for determining the strength of surface gravity on distant, faint stars. And painting more accurate pictures of stars is vital to studying the alien worlds that orbit them.

"If you don't know the star, you don't know the planet," University of British Columbia's Jaymie Matthews, a co-author on the research published Friday in Science Advances, said in a statement. You have to determine the strength of gravity on a star's surface before you can calculate its size and mass, assuming the star isn't close enough to measure directly.

Related: [NASA estimates 1 billion ‘Earths’ in our galaxy alone]

When scientists go looking for alien exoplanets — ones that sit far outside our solar system — they rely entirely on those planets' host stars. Measuring the way a star's light appears to flicker and dim from Earth's perspective allows scientists to calculate an astonishing number of things about the planets transiting around that star, including whether it's the right size and distance from its star to hold liquid water. But to make those calculations, you need accurate stellar measurements. Otherwise, you might misjudge the size of a planet. That's a problem when you're looking for worlds that could host life as we know it, since you want to track down planets that are small and rocky like Earth.

Lots of the stars imaged by the Kepler space telescope are too far away or dim for scientists to study the planets around them effectively. That's where the new technique, called the autocorrelation function timescale technique (timescale technique for short) comes in. Led by University of Vienna's Thomas Kallinger, researchers from Europe, Canada and Australia determined that using the timescale of variations in a star's brightness might be more accurate for determining gravity than the degree of brightness itself.

When they tested the timescale method on stars that are close enough to be studied with standard techniques, they found it to be about six times more accurate than the flicker method, which was developed in 2013 to study distant, dim stars by measuring the brightness of short variations caused by the bubbling of the star's gas.

As techniques like these continue to improve, scientists will be able to confidently study increasingly distant worlds, widening our net in the search for life.

Read more:

Why NASA's top scientist is sure that we'll find signs of alien life in the next decade

Why does Saturn's moon look so much like Earth?

Researchers mapped the weather of a planet outside our solar system — and it's pretty blustery

The most Earth-like planet we know about is probably being blasted with radiation

Many exoplanets may hide water in their thick clouds

This tiny star has a massive storm raging on it — just like Jupiter


Rachel Feltman is now an editor at Popular Science Magazine.

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