Buzz
This artistic rendering illustrates the white dwarf star (left) as it approaches its closest point to the black hole (right), being elongated by its immense gravitational forces. NASA/CXC/M. WeissFacing off with a black hole is no easy feat, and it's a battle that most stars lose. With their overwhelming gravitational pull, black holes can devour stars entirely. But one star managed to escape the black hole's clutches, if only briefly.
A study featured in the March edition of the Monthly Notices of the Royal Astronomical Society revealed how a red giant star, located in galaxy GSN 069 (roughly 250 million light-years away), ventured dangerously close to a supermassive black hole. It was caught in the black hole's grasp but managed to break free before being fully consumed.
The massive black hole, weighing about 400,000 times more than our sun, exerts such a strong gravitational pull that the star is trapped in an elliptical orbit around it. Once a red giant, the star's outer hydrogen-rich layers have been stripped by the black hole, leaving behind a helium-rich core, now called a white dwarf. It completes an orbit around the black hole every nine hours, and as it loses material, it merges with other surrounding debris, creating X-ray bursts that serve as signals to us on Earth.
"The dwarf star will desperately try to escape, but there's no way out. The black hole will slowly devour it, but it will never stop," said Andrew King, professor of theoretical astrophysics at the University of Leicester in the U.K. in a statement. King led the study that explained the cause of the X-ray flares.
The data was gathered using NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, an advanced X-ray space observatory.
While tidal disruption events, when a black hole rips a star apart, are not uncommon, the discovery of a star surviving its first encounter with a black hole is much rarer. This is mainly because such encounters are brief, lasting only about 2,000 years, a mere flicker in the grand timeline of the universe.
While more massive stars may frequently survive interactions with black holes, their long orbital periods would prevent scientists from observing multiple X-ray bursts, as we have in this case.
In the end, the white dwarf might eventually transform into a planet with a mass similar to that of Jupiter's, as per King's estimate. This transformation could span as long as a trillion years.
The encounter between this star and the black hole stands as an example of one of the universe's most cataclysmic events. It’s conceivable that the collision might generate gravitational waves, or "ripples" in space-time. These ripples are usually detected only during extreme events, like when neutron stars collide or when supernovae erupt.
