Starts With A Bang

LIGO’s Black Holes Probably Did Not Come From One Star (Synopsis)

Image credit: Swinburne Astronomy Productions.

“Even if the Fermi detection is a false alarm, future LIGO events should be monitored for accompanying light irrespective of whether they originate from black hole mergers. Nature can always surprise us.” -Avi Loeb

Ever since LIGO first announced the direct detection of gravitational waves from two merging black holes, the physics and astronomy community has been struggling to understand an unexpected phenomenon that appears to have come along with it: a short-period gamma ray burst.

An artist’s impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. This is the suspected origin of short-period gamma ray bursts. Image credit: NASA/CXC/GSFC/T.Strohmayer.

Arriving just 0.4 seconds after the gravitational waves did, the Fermi satellite’s detection doesn’t line up with models of black hole mergers. It’s thought that short-period GRBs originate from neutron star-neutron star mergers, and so seeing this has led to speculation of new physics, including from Avi Loeb at Harvard that perhaps LIGO’s twin black holes came from inside the same star. However, this explanation is exceedingly unlikely, and there are a number of astrophysical explanations that don’t require the new physics that Loeb’s explanation would.

Image credit: Image credit: NASA, ESA and G. Bacon (STScI), of a binary black hole. Loeb’s idea is that these binary black holes could exist inside a single star.

Go get the whole — mostly critical — story of why LIGO’s black holes probably didn’t come from the same star!