Neutrino with record energy could originate from exploded black hole
Earlier this year, evidence of the most energetic neutrino ever detected was presented. It could have been created during the explosion of a black hole.
(Image: MIT/Toby Gleason-Kaiser)
A neutrino discovered two and a half years ago, which literally shattered the energy record at the time, could have originated from an exploding black hole. At least, that is the opinion of two physicists from the Massachusetts Institute of Technology (MIT), who explain that this could answer several fundamental questions in physics. This would give us the first experimental evidence of so-called primordial black holes, the first measurement of Hawking radiation, and a strong indication that so-called dark matter is largely attributable to black holes. Just a few days ago, another research group claimed that the explosion of a tiny black hole should have been detectable long ago.
Unexplained record find
The record-breaking particle was found by the European observatory Cubic Kilometre Neutrino Telescope (KM3NeT) on February 13, 2023. It had an energy of 220 petaelectronvolts, which was more than twenty times the energy of the most energetic neutrino found to date. These electrically neutral, largely massless particles are released during particularly high-energy events in space, about which they are expected to reveal more. However, detecting them is extremely difficult because they move at nearly the speed of light and almost never interact with atoms. This means they can even pass through the Earth more or less unhindered. Only very special observatories can detect them at all and determine their properties.
The research team at MIT now believes that the record-breaking particle may have been created during the explosive end of a tiny black hole. They refer to these as primordial black holes. According to the relevant theories, these tiny objects were created from existing matter immediately after the Big Bang and not, like others, from the collapse of stars. The term is derived from the Latin word "primordium" ("first beginning"). So far, these PBHs (abbreviation of the English term) have only been described theoretically; it is unclear whether they really exist. Until now, it has also been assumed that they should explode comparatively rarely, which would make detection extremely unlikely.
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British physicist Stephen Hawking recognized that black holes are not completely invisible, but should emit particles. This Hawking radiation was named after him, but because the quantities involved are extremely small and large or supermassive black holes are very far away, it was previously considered impossible to detect them. However, if primordial black holes exist, this would be different. The tiny objects should not only shrink as they emit particles, but also become increasingly hotter. If it ends up smaller than an atom, it should disappear in a final explosion, explains MIT.
Much more evidence needed
Alexandra Klipfel and David Kaiser have now calculated which particles should be released in such explosions. Among other things, these would be 1020 neutrinos, each with an energy of about 100 petaelectronvolts. This is exactly in the range of the record particle from KM3NeT. According to this, the explosion would have occurred at a distance of 2000 AU, which is two thousand times the distance between Earth and the Sun. In addition, the two have calculated how many primordial black holes would have to explode in a given area to explain similar neutrino detections by the IceCube detector in the Antarctic ice. According to their calculations, 1000 PBHs would have to explode each year in a cube with an edge length of one parsec (3.26 light-years) in our part of the Milky Way.
However, this is still a theory; to confirm it, significantly more discoveries of such high-energy neutrinos would be needed. Just a few days ago, a research team from the nearby University of Massachusetts presented its research, which also deals with the final explosions of primordial black holes. According to the team, under certain circumstances, these would explode much more frequently than previously assumed. If this is true, the probability of observing such an explosion in the next ten years would be over 90 percent, according to the study. The research on neutrino findings, conducted simultaneously at MIT, has now been published in Physical Review Letters.
(mho)
