Technology

Astronomy: measuring star gravity to search for alien planets

Researchers believe they've come up with a new, more accurate method for determining the strength of surface gravity on distant, faint stars.

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," said University of British Columbia's Jaymie Matthews, co-author of the research published in late December in Science Advances. "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."

A new way of measuring star gravity will aid in the hunt for alien planets.
A new way of measuring star gravity will aid in the hunt for alien planets. Photo: Supplied

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 orbiting around that star, including whether it's the right size and distance away 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 the 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. 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.

The Washington Post