An image of the Andromeda galaxy taken with the hyper-suprime cam. A recent snapshot of Andromeda found only a signal that could have come from a medium-sized black hole that had formed shortly after the Big Bang.
Credit: Copyright HSC-SSP and NAOJ
One of Stephen Hawking's most famous theories of dark matter ̵
The results do not completely rule out Stephen Hawking's famous notion. However, they suggest that the original black holes must be really tiny to explain the dark matter.
Dark matter is called a physicist to explain a particularly mysterious phenomenon: everything in the universe moves, moves and turns as if there were more mass than we can determine. Dark matter explanations range from ghostly particles, called neutrinos, to unknown particles, to new physical laws. In the 1970s, Stephen Hawking and his colleagues hypothesized that the Big Bang may have created a large number of relatively small black holes – each about the size of a proton. These tiny, ancient black holes would be hard to spot and exert a great attraction on other objects – the two known properties of dark matter. [The 11 Biggest Unanswered Questions About Dark Matter]
Previously, this theory could only be tested for original black holes that are heavier than the Moon. However, with the improvement of technology, scientists have been able to take sharper pictures of the universe. The Subaru Telescope Hyper Suprime Cam (HSC) digital camera in Hawaii is an advanced imaging technique that lets you capture the entire Andromeda galaxy (closest to our galaxy) in one image. Masahiro Takada and his team from the Kavli Institute of Physics and Mathematics of the Universe in Japan used this camera to search for original black holes. Their results were published earlier this month in the journal Nature Astronomy.
However, black holes do not emit light, supermassive black holes, like the heart of the galaxy Messier 87, are lined with bright disks of hot matter. However, original black holes are billions of times smaller and have no visible, luminous matter surrounding them. The search for small black holes means looking for places where their strong gravitational fields bend the light – a phenomenon called microlenses.
Telescopes find microlens black holes by absorbing many different images of a star over time. A black hole that passes in front of this star distorts its light and makes it blink. The smaller the black hole, the faster the flash. "If a microlens object has a solar mass, say a solar mass," Takada told Live Science, referring to the mass of the Sun, "the timescale [of the microlensing ‘flash’] is like a few months or a year." But the original black holes they were looking for had only a small fraction of that mass, about the mass of the moon. That is, their flashes would be much shorter. The HSC was "unique," Takada said, allowing them to shoot all the stars in the Andromeda galaxy simultaneously, in stunningly fast (for astronomers) exposure intervals – each interval lasted only two minutes.
Takada and his team made about 200 pictures of the Andromeda galaxy over a 7-hour clear night. They found only one possible microlens event. If the original black holes were a significant part of the dark matter, they should have seen about 1,000 microlens signals.
"Microlenses are the gold standard for detecting or eliminating black holes," said Simeon Bird, a black hole physicist at the University of California – Riverside who was not involved in the work. "This work excludes primitive black holes as dark matter in a series of masses where the previous constraints were not as strong or as robust as this new one – it's a very nice result."
Was this the last nail in the coffin? Is Hawking's theory really dead? Not so, according to Bird and Takada, who say that original black holes in a particular set of masses are still not completely eliminated as candidates. [Stephen Hawking’s Most Far-Out Ideas About Black Holes]
"There are still some masses where the constraints are weak, about 20 to 30 solar masses," Bird told Live Science. "That could still be 1% to 10% of the dark matter … and there is still a window with lower masses, like the mass of a very small asteroid."
"Our physicists are very excited because there is still a window," said Takada. The data can not exclude these tiny tiny black holes, as the flashes of these black holes would be far too short. "That's why we have to imagine another method."
However, there was a "lightning bolt" discovered in their survey, and although it was a single preliminary result, it could be incredibly important: the very first evidence of an original black hole that is groundbreaking confirmation of some of Hawking's work
"Only one observation is not so convincing," Takada said. "We need more observations to confirm that. If it really was [a primordial black hole]we should continue to find the same "as they continue to use the HSC to search for more microlenses.
Originally published on Live Science .