A monstrous black hole—17 billion times the mass of the Sun and possibly the largest ever detected—appears to be too big for its galactic home, leaving astronomers scratching their heads about its very existence.
The cosmic behemoth, at the heart of a distant galaxy, is estimated to be 4,000 times larger than the black hole at the center of the Milky Way. It’s officially ranked the second-largest black hole known; estimates on the current record holder span a wide range, from 6 to 37 billion solar masses.
This surprising find comes on the heels of the discovery earlier this week of the largest blast ever seen emanating from a black hole.
However it’s not the sheer size that has astronomers stumped, but the black hole’s mass in relation to its host galaxy, known as NGC 1277, some 250 million light years away in the constellation of Perseus.
The black hole makes up 14 percent of its galaxy’s mass, versus the usual 0.1 percent.
“Normally a black hole is tiny compared to the galaxy it sits in, but this one is really big, so much so that most of the stars in this galaxy probably feel the black hole’s attraction,” said Remco van den Bosch, astronomer at Germany’s Max-Planck Institute for Astronomy and lead author of the study published this week in Nature.
RETHINKING GALAXY EVOLUTION
Using the Hubble Space Telescope and the Hobby-Eberly Telescope in Fort Davis, Texas, the international team of astronomers had been on the hunt for supermassive black holes, surveying close to 800. They were surprised to find a total of six diminutive galaxies that appear to harbor the supergiant variety.
“We set out to find the biggest black holes by targeting mostly big galaxies,” said Van den Bosch. “Now that we have found that these crazy kind of galaxies exist, we want to know how they form and how uncommon they are.”
Van den Bosch believes that since the vast majority of black holes found at the centers of galaxies account for only about 0.1 percent of their mass, this new, unexpectedly obese type of black hole could very well overturn models of galaxy evolution.
“We have expected that galaxies and black holes co-evolve together, through some kind of self-regulation & feedback mechanism,” he said. “But now we found systems where somehow the black hole could grow without forming many stars in the galaxy.”
Jenny Greene, a Princeton University astronomer not connected to the study, agreed that the new finding will force researchers to think hard about their ideas of how supermassive black holes are connected to their parent galaxy.
“In general black holes make up a fixed fraction of the galaxy mass, suggesting that they all form in a similar way, but this observation forces us to think again about that process,” she said.