NASA’s Exoplanet-Hunting Spacecraft Captures ‘Melody’ of a Red Giant Star Interacting with Its Black Hole Companion

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers have uncovered intriguing details about a red giant star in a binary system with a black hole. This red giant, located about 3,800 light-years away in the constellation Centaurus, has shown signs of a turbulent past. It seems to have merged with another star, revealing a complex history.

The TESS team, led by Daniel Hey from the University of Hawaii Institute for Astronomy, studied “starquakes”—oscillations within the star that reveal its internal structure, much like how earthquakes help us understand Earth’s interior. “These vibrations told us something unexpected about this star’s history,” Hey noted.

Upon examining the red giant’s composition, the team found it contained heavy elements typically found in older stars. Surprisingly, this star is estimated to be just 5 billion years old, while our Sun, which formed about 4.6 billion years ago, won’t become a red giant for another 5 billion years. “It’s rare to find young stars that are alpha-rich,” Hey explained. This suggests that the star didn’t evolve in isolation; it likely gained mass during its interactions with the black hole.

Further investigation revealed that this red giant spins much faster than typical stars of its age—once every 398 Earth days. Joel Ong, a NASA Hubble Fellow, speculated that such rapid rotation couldn’t be solely due to the star’s nascent conditions. “The star must have been spun up through tidal interactions with its companion,” Ong said, reinforcing the notion of a complicated evolutionary history.

Interestingly, there’s another black hole system, Gaia BH3, discovered by the same team. It’s located just 2,000 light-years from Earth and features a companion star that’s even more unusual. This star is low in elements heavier than hydrogen and helium, yet it shows no observable oscillations.

The mysteries surrounding Gaia BH2 and Gaia BH3 could provide new insights into binary systems with black holes that aren’t actively consuming their companion stars. Researchers are keen to continue monitoring Gaia BH2, hoping to learn more about its starquakes and understand its past mergers.

This research sheds light on the intricate lives of stars and their companions, showing that the universe is full of surprises waiting to be uncovered. For more details, you may check the findings in The Astronomical Journal here.

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