Computer simulation shows a star being shredded by the gravity of a massive black hole and ejecting the debris at high speeds.The blue dot pinpoints the black hole's location. Credit: NASA, S. Geravi.
This video simulates the murder of a star at the hands of a black hole. A supermassive black hole lurking in the center of a galaxy 2.7 billion light years away snatched a passing star into its orbit, ripped it to shreds and devoured its remains before belching gas into the universe.
"We had to monitor hundreds of galaxies before we were lucky enough to observe this event," said Suvi Gezari, associate research scientist of physics and astronomy at Johns Hopkins University.
Her team's paper on the stellar homicide was published Wednesday in the online edition of the journal Nature. Gezari said this event has taught them what kinds of stars are likely prey for black holes, how black holes consume stars and what to look for when these catastrophic events happen.
The victim was not like our sun. Gezari described it as a "puffy" red giant, a star in its last stages of life that is mostly helium with a outer layer of hydrogen.
The black hole, which is 3 million times the density of our sun, first stripped that hydrogen layer from the star with its powerful gravitational force. Then the remains of the star were pulled into orbit around the black hole. Like water circling a drain, it moved faster as it got closer to the center. As it moved faster, it grew hotter, until it finally fell into the center of the black hole.
When that happened, half of the remaining helium gas from the star spewed out at 5,500 miles per second, forming a giant flare of visible and ultraviolet light which the space-based GALEX telescope and the Earth-based Pan-STARRS1 telescope captured in the summer of 2010.
When the bright, hot flare of helium appeared, Gezari wasn't sure what it was. It took a year for the flare to dim enough for astronomers to sort through the evidence of the star's death.
"We're seeing the messy carnage going on from a star going so close to the black hole," Gezari said. "This is the first time we have enough information to determine how big the black hole is and what kind of star has this kind of catastrophic event."
Black holes like this exist all over the universe, lurking in the centers of galaxies; there's one at the center our Milky Way. But stars only pass close enough to these supermassive black holes once every 100,000 years, so scientists are never sure when or where they can witness such an event.
But don't worry -- these black holes can't consume entire galaxies.
"Most of the time the black hole is sitting around starved of fuel, hungry," Gezari said. "This is more like snacking along the way."
