60-Second Space

Giant Black Hole May Be Fugitive

The black hole in galaxy NGC 1277 is way more massive than usual. Astronomers hypothesize it was ejected from another galaxy before settling in its new home. John Matson reports

Black holes tend to be pretty massive. The one at the center of our galaxy is about four million times the mass of the sun.

But that’s puny compared with the whopper that researchers discovered last year in an otherwise unremarkable galaxy called NGC 1277. Its black hole is some 17 billion times the mass of the sun.

By typical standards, such a black hole is about 100 times too massive for that galaxy.

The discovery got researchers wondering how the mismatch came about.
One idea—albeit a speculative one—is that the black hole actually came from a different galaxy. 

Say the black hole formed from the merger of two smaller black holes in a larger galaxy nearby. The recoil from that violent event could have flung the ultramassive black hole into space. Where it wandered, among a cluster of galaxies, before settling into a new home in NGC 1277. The hypothesis is in the Astrophysical Journal Letters. [Gregory A. Shields and Erin W. Bonning, A Captured Runaway Black Hole in NGC 1277?]

The paper’s authors note that the runaway black hole scenario requires the confluence of seemingly unlikely events. But the universe is a big place, where improbable things happen all the time. Look at you.

—John Matson

[The above text is a transcript of this podcast.]

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