We still do not know what dark matter is, but we can strike a line through one option. It is not, as per a theory proposed by brilliant Stephen Hawking, and a bunch of teeny-tiny microscopic black holes.
In the most rigorous test of the theory to date, an international team led by researchers from the Kavli Institute for Physics and Mathematics of the Universe (IPMU) in Japan has been searching for the telltale sign of such minuscule black holes, the result was pretty damning
The scientists were hunting for a particular flicker of stars in a nearby galaxy – the way light would appear to us if a black hole less than a tenth of a millimeter were passing in front of it.
A black hole of that size may seem ridiculous, but the concept actually stems from an elegant theory by Hawking, who was trying to tackle our massive dark matter problem.
The problem is this: based on our observations of the
In a paper published in 1
Just after the Big Bang, the theory goes, when the universe came into being, there could have been regions of matter in the primordial soup that were denser than others – dense enough for gravitational collapse. -8 kg.
Now, even a tiny black hole has a lot of mass. A black hole with an event horizon of 0.1 millimeters in diameter would have a mass of over 67 quintillion metric tons. So, if there were a bunch of these tiny black holes out there – and they had not evaporated due to Hawking radiation – they could, conceivably, account for the mass we can not see
And, if there was a a bunch of these black holes out there, zipping around at the tremendous speeds calculated by Hawking, we might see them bending the light of objects they move in front of, an effect called gravitational lensing
It's this effect the team focused their efforts on. Using the Hyper Suprime Cam on the Subaru Telescope at Mauna Kea in Hawaii, researchers from Japan, India and the US observed the whole of the nearby Andromeda Galaxy, capturing 190 consecutive images over a total of seven hours
If a primordial black hole was to move between us and a star, it's expected that the star would flicker and brighten for a few minutes to hours as the black hole's gravity magnified its light
The team predicted that the abundance of black holes smaller than the Moon needed to produce the effect of dark matter would result in about 1,000 lensing events.
But observations made just one potential event – meaning that primordial black holes can be responsible for no more than 0.1 percent of dark matter. (19659003) It is unlikely that dark matter will not be made of teeny black holes
It's unlikely that's the ultimate nail in the theory's coffin – scientists like to be extremely thorough after all.
The Nature of Astronomy