AUDIE CORNISH, HOST:
A hole is missing, a very big hole.
AILSA CHANG, HOST:
A black hole, to be precise - more massive than a billion suns. You see, nearly every large galaxy appears to harbor a supermassive black hole at its center.
CORNISH: But when astronomers trained telescopes on one galaxy some 3 billion light years away called...
KAYHAN GULTEKIN: Abell 2261-BCG.
CORNISH: ...Astronomer Kayhan Gultekin of the University of Michigan says they found a puzzle.
GULTEKIN: We saw that there used to be a black hole 50 million years ago, but there is no evidence for a black hole being there currently.
CHANG: Where did it go? Well, in a paper published on January 1 in The Astrophysical Journal, he says the black hole could have been flung out of its galaxy by some ancient collision with another black hole. But so far, they haven't found the galactic wreckage to prove it.
CORNISH: Yale University astronomer Professor Priya Natarajan has another hunch. She says the black hole could still be there; it's just hiding from our X-ray telescopes.
PRIYA NATARAJAN: Most black holes are in one of two states - they're either fasting or feasting. When they're feasting, it means they're actively growing. Their gas is being gobbled in, and you would see the gas on its way in in the X-rays.
CHANG: But if the black hole is fasting, like the one in our galaxy, the Milky Way, she says it would be tough to see with our current instruments.
NATARAJAN: Ultimately, we need evidence, right? So we can speculate all we want, but this is very tantalizing.
CORNISH: For now, the galaxy will remain a mystery.
GULTEKIN: A mystery is always fun for a scientist.
CORNISH: Meanwhile, if you have any information as to the whereabouts of this black hole, please call astronomer Kayhan Gultekin in Ann Arbor.
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