Stellar pulses are transformed into a celestial symphony

A new NASA video showcases the whirring symphony of stars in our cosmic neighborhood. 

Although it usually hunts for alien worlds, or exoplanets in the nearby universe, one NASA mission is also capable of measuring the vibrations produced by behemoth celestial bodies known as red giant stars

The Transiting Exoplanet Survey Satellite (TESS) mission, which launched in April 2018, is designed to find exoplanets. The technique it uses to find these worlds is called the transit method, and it involves surveying nearby stars and waiting to see if their brightness dips at all. These dips are caused by a planetary body passing in front of the star's face, from our perspective in space. 

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An illustration of red giant stars.  (Image credit: NASA's Goddard Space Flight Center/Chris Smith (KBRwyle))

Because TESS is already poised to observe changes in stars caused by orbiting exoplanets, it was also capable of detecting the oscillations in the bodies of red giants. 

"Our initial result, using stellar measurements across TESS's first two years, shows that we can determine the masses and sizes of these oscillating giants with precision that will only improve as TESS goes on," said Marc Hon, a NASA Hubble Fellow at the University of Hawaii in Honolulu, who presented the new research this week during the second TESS Science Conference. Hon commented in an Aug. 4 NASA statement about the new work. 

According to NASA, a star oscillates when the gas it contains heats up, rises, then cools down and sinks. These pulses can be translated into sound waves. 

Just as a person may have their eyes closed but still recognize that the sound of two similar types of instruments make different sounds, like a violin and a cello, astronomers can use these stellar waves to determine the makeup and dimensions of red giants in contrast to other kinds of stars and to one another. 

This subfield of astronomy, dubbed asteroseismology, "can help determine fundamental properties for large numbers of stars with accuracies not achievable in any other way," NASA said in the statement.

The team hotwired the TESS mission to look for something new by teaching a computer, via machine learning, how to make decisions based on patterns. In this case, artificial intelligence allowed the computer to hone in on red giant stars throughout a sample of TESS star data. 

Once researchers finished this first stage, they plotted the distances of these more than 150,000 red giant stars. Next, they turned to the Gaia mission. Gaia is a European Space Agency (ESA) telescope that is creating the most-detailed picture yet of the Milky Way galaxy. 

Astronomers think that red giants, which are large, should sit closer to the plane of the Milky Way. So, Hon's team coupled their findings with Gaia's mission.

"Our map demonstrates for the first time empirically that this is indeed the case across nearly the whole sky," co-author Daniel Huber, an assistant professor for astronomy at the University of Hawaii, said in the NASA statement. "With the help of Gaia, TESS has now given us tickets to a red giant concert in the sky."

The new work, which appeared on the preprint server, has been accepted for publication in The Astrophysical Journal.

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Doris Elin Urrutia
Contributing Writer

Doris is a science journalist and contributor. She received a B.A. in Sociology and Communications at Fordham University in New York City. Her first work was published in collaboration with London Mining Network, where her love of science writing was born. Her passion for astronomy started as a kid when she helped her sister build a model solar system in the Bronx. She got her first shot at astronomy writing as a editorial intern and continues to write about all things cosmic for the website. Doris has also written about microscopic plant life for Scientific American’s website and about whale calls for their print magazine. She has also written about ancient humans for Inverse, with stories ranging from how to recreate Pompeii’s cuisine to how to map the Polynesian expansion through genomics. She currently shares her home with two rabbits. Follow her on twitter at @salazar_elin.