A New Study Rules Out Black Holes as Explanation for the Universe's Missing Dark Matter

Wednesday, 03 October 2018 - 2:00PM
Astronomy
Space
Black Holes
Wednesday, 03 October 2018 - 2:00PM
A New Study Rules Out Black Holes as Explanation for the Universe's Missing Dark Matter
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NASA/JPL/CalTech
A new discovery has destroyed astronomers' hopes of accounting for what it is or how it's connected to the observable universe. The theory was that dark matter (which is estimated to make up 84% of the universe's matter) was contained in a huge number of previously invisible black holes scattered across the universe. However, based on a new study from the University of California, Berkeley, these huge numbers of black holes don't exist, nor do their hidden repositories of dark matter.

The study is based on observations of gravitational lensing, a phenomenon where the light from distant objects is bent by the gravity of a massive body that lies between the object and the observer. In this case, researchers used the light of over 1,000 Type Ia supernovas – some of the brightest things in the universe – and measured their brightness against what was expected. If there were any hidden black holes in the way (which, based on their supposedly large numbers, there should be), that light would be brightened by a small, but significant amount.

Unfortunately, these previously invisible black holes didn't appear to exist. Even if they were small, their gravitational lensing effect would have left its fingerprint on the light coming from the supernovas. According to the lead author on the study, Miguel Zumalacárregui: "You cannot see this effect on one supernova, but when you put them all together and do a full Bayesian analysis you start putting very strong constraints on the dark matter, because each supernova counts and you have so many of them."

The ultimate result? If black holes do in fact contain portions of the universe's dark matter, it's only about 40% of it at best—and a follow-up study in the works may reduce that number to 23%, tops. Where's the rest? Astronomers don't know, but they do know black holes aren't the definitive answer.

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