Waiting for the Andromeda galaxy’s stars to twinkle may have extinguished hope for tiny black holes being a significant dark matter candidate
Should a black hole drift in front of a star, it could trigger a microlensing event, so astronomers set out to take a statistical stab at estimating the number of primordial black holes in Andromeda [Kavli IPMU]
Using the Andromeda galaxy as a huge detector, astronomers have taken a stab at seeing the unseeable — possibly disproving a hypothesis first put forward by the late Stephen Hawking 45 years ago.
According to Hawking’s work, the universe should be filled with black holes that were formed at the beginning of time, when the universe was a chaotic soup of energy just after the Big Bang. Known as “primordial” black holes, these ancient objects are hypothesized to invisibly occupy modern galaxies, including our own, boosting their dark matter mass.
These black holes aren’t the supermassive monsters that lurk in the centers of most galaxies; they’re not even stellar-mass black holes, formed after massive stars go supernova. Primordial black holes are much smaller than that, having leaked most of their mass via Hawking radiation since their formation 13.8 billion years ago. ...