Millions of Stars Can Now Be Weighed, a Vital Clue in the Search for Life

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The characteristics of a star determine characteristics of its planets. NASA

Astronomers have developed a new way of figuring out how much mass a star contains. This "vital sign" that can tell them as much about a star as it tells a doctor about a patient.

The breakthrough mass-measuring technique, described in a new paper is particularly valuable because it works accurately with individual stars at any distance. Like humans, stars tend to come as singletons and as pairs.

Astronomers already have a way to calculate the mass of stars that are paired. The dance that takes place between them provides all the information necessary. But no one knew how to obtain the same measurement for the singletons.

That lack of know-how was particularly frustrating for the search for life. Red dwarfs are the type of stars many scientists see as the most likely candidates for finding life beyond our solar system. And these stars tend to come as loners, not in pairs. So it was particularly frustrating that scientists hadn't found any techniques that were very effective for stars that aren't part of a pair.

The team behind the new paper, accepted for publication by The Astronomical Journal, based their approach on calculating mass using characteristics that are easier to measure directly: the star's size and its surface gravity. That relied on previous work by the same scientists, who figured out how to calculate surface gravity (another sort of "vital sign" for stars) based on how a star's brightness flickers.

Once they settled on their roundabout way to calculate mass, they vetted the technique by using it on 525 stars that have already been well studied by the Kepler Space Telescope.

The new technique could tell scientists more about stars themselves. In particular, the team has their eyes set on a group of stars with masses below that of our sun that appear to be oddly puffy, taking up more space than scientists would expect. It's a common characteristic, but scientists have no idea how it happens. Nailing down size, mass and age for a large number of stars could help them crack the mystery.

Read more: NASA Kepler Googled an Alien Solar System and Found It Matches Our Own With a Record Eight Planets

But in particular, the authors are focused on how their technique will fit in with new data from two key astronomy projects. Gaia, a European satellite, is conducting a "galactic survey" that should tally a billion stars by the time the project ends. TESS, a planned NASA mission, will look for exoplanets by watching for tiny, repeated dips in the brightness of 200,000 stars as a planet passes in front of one.

And stellar mass and planetary mass are related, being able to apply the new technique to this expected data will let scientists get a better picture of new exoplanets (like the record-breaking Kepler-90i announced yesterday). Using less accurate techniques to calculate the star's mass means a less accurate sense of the planets themselves—and that could mean under- or overestimating the probability of a planet being habitable. This new method could change that.