On the night of November 23, 2014, a powerful telescope on Mauna Kea in Hawaii was trying to identify the enigmatic movements of a black hole traveling through space. In the seven hours the telescope looked at the cosmos, it may have caught one, as an Earth-sized structure eclipsed a star in our nearest galactic neighbor, Andromeda, about 2.5 million light-years away. . Against the background of the 188 relatively bland images taken of the galaxy that night, the candidate event of the black hole was a moment of literal enlightenment.
“When it is right along the line of sight, the light bends [the black hole]. Not only the rays of light that direct you to be with you, but also those that would have passed beyond you lean towards you, “said Alexander Kusenko, an astrophysicist at UCLA and the Kavli Institute for Physics and Mathematics of the Universe, in a video. . call. “It will make the star look brighter for a second. It’s a little counterintuitive. “
Kusenko is the lead author of a recent paper discussing the event, published in the journal Physical Review Letters in October. Research suggests that between some and all of the dark matter in the universe could be explained by primordial black holes – small hypotheses and very old versions of the classical cosmic character that was only imagined directly for the first time in 2019. All black holes, regardless of their size, are celestial objects that exert so much gravitational force that nothing, not even light, can escape them.
One idea is that at the beginning of the universe, slight fluctuations in density in the incredibly densely inflated universe would have been enough to generate black holes in pre-stellar plasma, especially if they interacted with heavy particles by an unknown force. (Known black holes are usually made up of collapsing stars.)
“If you take a spoonful of primordial plasma, it’s almost a black hole,” Kusenko said, referring to the initial density of the universe. “Squeeze it a little and the light won’t go out.”
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Some of these theoretical black holes would have been of a certain critical size, according to Einstein’s theory of gravity, to be perceived as constantly expanding to an observer in the black hole – while remaining a static dimension for the outside observer. This idea may give rise to the notions of “universes for children” within us, but keep in mind that primordial black holes are themselves only theoretical at the moment.
And this is the immediate concern of Kusenko’s team: proof of their existence. Primordial black holes should be numerous if they explain a certain amount of dark matter in the universe – mysterious things that seem to make up about 27% of the universe – but too small to be detectable, as their counterparts have confirmed.
Kusenko and his colleagues (UCLA and Kavli IPMU researchers participated in the October paper) cast a wide net for black hole candidates using Hyper Suprime-Cam, a nearly 6-foot-long barrel attached to the nearly 30-foot mirror. meters the Subaru telescope on Mauna Kea. The camera is able to imagine the entire Andromeda galaxy every few minutes. Since a candidate for a primordial black hole was chosen in the seven-hour tour of the cosmos in 2014, Kusenko hopes that future observations will be able to collect more events to unpack.
The 2014 observation was not easy to find in all the data. The team narrowed down a catalog of more than 15,000 candidate stars to check for slight deformation, and in the process found nearly 50 “imposter” events caused by bright stars, among others. An impostor was even caused by a passing asteroid. But after a lot of star sorting, one candidate seemed in good faith.
If more candidate events are identified, there will be more clue to the team’s theory about a lot of miniature black holes that take into account overweight measured in many galaxies (it is that additional gravity that led scientists to the existence of dark matter in the 1970s). To put things in perspective, the smallest known black holes are in the realm of 5 solar masses (ie five times the size of the Sun). The recent candidate for the black hole was only the size of our planet.
If an Earth-sized black hole sounds hard to believe, well, it’s not even the smallest proposed black hole. Last year, physicists suggested a black hole the size of a bowling ball to explain a hypothetical object in our solar system known as the New Planet.
Kusenko’s team made another round of remarks at Mauna Kea at the end of 2020 and now has to do a thorough job of reviewing the data. We could know at the end of this year if they found potential black holes“And our fingers are firmly crossed for good news.”