New Method for Measuring the Surface Gravity of Distant Stars: Flicker

A star's surface gravity can tell astronomers quite a bit about the star itself. It can allow scientists to calculate its physical properties and even assess its evolutionary state. Now, researchers have discovered a clever new way to slice and dice the flickering light from a distant star that reveals the strength of the gravity at its surface.

There are three traditional methods for estimating a star's surface gravity: photometric, spectroscopic and asteroseismic. Photometric methods look at how bright a star is in different colors. This distribution is linked to its surface gravity, temperature and chemical composition. While relatively easy to perform, though, it's not very accurate. The spectroscopic method, in contrast, is more involved and is limited to relatively bright stars. It closely examines the narrow spectral bands of light emitted by the elements in the star's atmosphere. Finally, asteroseismology is the most accurate, but the measurements are very difficult to make; it's restricted to several hundred of the closest, brightest stars.

Now, researchers have developed the new technique: the flicker method. This technique looks at variations in the star's brightness. In this case, it zeroes in on variations that last eight hours or less. These variations appear to be linked to granulation, the network of small cells that cover the surface of a star that are caused by columns of gas rising from the interior.

"The spectroscopic methods are like surgery. The analysis is meticulous and involved and very find-grained," said Keivan Stassun, one of the researchers, in a news release. "Flicker is more like ultrasound. You just run the probe around the surface and you see what you need to see. But its diagnostic power--at least for the purpose of measuring gravity--is as good if not better."

In fact, the researchers found that the uncertainty of the new method was less than 25 percent. That's far better than both the photometric and spectroscopic methods. The main limitation of this new technique, though, is that it requires extremely high quality data taken over long periods. However, these are just the types of observations that were made by Kepler while it was searching for exoplanets.

The new method could allow researchers to learn a little bit more about stars. This, in turn, could allow them to know more about the exoplanets surrounding them.

The findings are published in the journal Nature.

Want to learn more about the flicker method? Check out the video below, courtesy of YouTube.