Is the universe's dark matter hiding in primordial black holes?
A new model by a team of scientists led by Yale University suggests that the ever elusive dark matter that has so far escaped the detection of scientists may be trapped inside primordial black holes left over after the Big Bang.
If or when the James Webb Space Telescope is fully commissioned and begins its observations into the evolution of the early universe, it may be able to shed light on one of the great mysteries of modern physics: does dark matter exist and, if so, what is it?
Dark matter is, essentially, the greatest rounding error ever to occur in the history of science. As astrophysicists started to probe into the structure of the universe and how it evolved from the Big Bang 13.8 billion years ago, they developed an increasingly detailed picture of how the universe evolved from its first instant of being.
The problem was that physics simply could not properly explain how the universe came to be as observations described it. Everything from the formation of stars and galaxies to the nature of cosmic background radiation could not happen with the amount of matter that we can observe. In fact, current theories suggest that the matter and energy deficit is one of 95 percent, with ordinary matter and energy comprising the remaining five percent.
This massive deficit needs to be explained for more reasons than being untidy. It could also be a clue as to the nature of the universe. It was a flaw in Maxwell's equations that suggested the existence of electromagnetic radiation. The planets Uranus and Neptune were discovered because Saturn's orbit wasn't as calculated, and it was light not behaving as it should that helped produce Einstein's theory of relativity.
On the other hand, if there isn't something making up that 95 percent deficit of matter and energy, then scientists have fundamentally screwed up on a very basic level.
The present theory is that dark matter makes up around 85 percent of the matter in the universe. Though it has never been observed, dark matter is hypothesized to be made up of some form of exotic matter, including sterile neutrinos, weakly interacting massive particles (WIMPS), or axions that have no interaction with any form of electromagnetic radiation.
Put simply, dark matter cannot absorb, reflect, or refract light or any other part of the spectrum. The only clue that it exists at all is that it only interacts with normal matter and energy by way of gravity. That makes it extremely difficult to detect, much less learn anything about.
According to the Yale team, the answer to the mystery of dark matter doesn't lie in exotic particles, but in primordial black holes ranging in size from microscopic specks to billions of miles in diameter. These black holes are areas of spacetime where large bodies of matter have collapsed in on themselves, leaving behind a gravity well so strong that not even light can escape from it.
Back in the 1970s, physicists Stephen Hawking and Bernard Carr suggested that during the first second of the universe's existence after the Big Bang, there could have been fluctuations in its density with some regions cluttered enough to produce black holes. This hypothesis didn't catch on, but the new Yale study has tweaked the idea and calculated that if most of the primordial black holes had an initial mass of about 1.4 times that of the Sun, it could account for all the dark matter – especially as they went on to absorb more gas or even stars in their vicinity. In addition, they could have acted as the seeds around which galaxies formed and created the supermassive black holes found at many galactic cores.
If this is so, then the James Webb Space Telescope could provide some confirmation of the theory by gathering data on how stars, galaxies, and planetary systems formed as its infrared sensors probe the edges of the universe, where light from the universe's early history is still streaming to us.
"If the first stars and galaxies already formed in the so-called ‘dark ages,’ Webb should be able to see evidence of them," says Günther Hasinger, ESA’s director of science and study member.
The research will be published in the Astrophysical Journal.
Source: Yale University