We found the most powerful accelerator in the galaxy. No one would expect him there
Molecular Cloud Taurus Molecular Cloud. Credit: ESA / Herschel / NASA / JPL-Caltech / R. Hurt.
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Cosmic radiation is raining on Earth from various sources. Sometimes particles with really extreme energy appear in it. Astronomers have always wondered where high-energy cosmic ray particles actually come from. However, the search for their resources is usually quite complicated. The marvelous HAWC (High Altitude Water Cherenkov Experiment) observatory, which detects Cherenkov radiation, has now come up with a very interesting candidate for such an extreme source. And it’s really quite unexpected. The most powerful particle accelerator in the Milky Way may be hiding in a boring molecular cloud that is everywhere.
HAWC Extreme Observatory. Credit: Jordanagoodman / Wikimedia Commons.
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The most powerful terrestrial particle accelerator, now the legendary LHC at European CERN, can accelerate particles by carrying energy around 13 teraelectronvolts, or 13 TeV. But there are much more powerful “natural” particle accelerators in space. Their performance is more than a thousand times higher than our LHC and is in the order of petaelectronvolts (10 to fifteen). The question is, what are these cosmic “pevatrons”.
The search for sources of cosmic radiation is much more complicated than it seems at first glance. High-energy cosmic ray particles are practically unmissable, but they are also usually electrically charged. This means that they are exposed to immense magnetic fields that intersect the Galaxy. In other words, these particles do not fly straight.
Some molecular clouds play nothing. Credit: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI / AURA).
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Nevertheless, it is possible to track the paths of cosmic ray particles. When they hit some interstellar material, gamma radiation can be emitted. And these traces of gamma radiation can be traced – and with a little luck they can lead to the original source of cosmic radiation. This is the HAWC observatory, located on the slope of the Mexican Sierra Negra volcano, working in this way, by monitoring traces of gamma radiation. Eventually, she led an international team of experts to a source of gamma radiation with energies over 200 TeV. And so strong gamma radiation could only create extreme cosmic radiation from the pevatron, ie energies in the order of PeV.
The gamma source in question is designated HAWC J1825-134. From our point of view, it is located roughly in the direction of the center of the Milky Way. The problem is that there is nothing nearby that would immediately strike us in the eye and look like a pevatron. For example, we would expect the remnants of a recent supernova or, for example, a wildly spinning pulsar. But there is no such thing in a given area of the universe. Strange as it is, it looks as if the pevatron is a completely ordinary molecular cloud. Its density is estimated by scientists at about 700 protons per centimeter of the cubic universe.
But it doesn’t make sense. Molecular cloud, that’s such a big nothing. Like steam over a pot. There may be some newborn stars in the cloud in question, but no stellar child should shout nearly as loud as a pevatron. The authors of the study admit that they have no idea how the pevatron works, if they are looking for the right place. There seems to be something, some object or process in the molecular cloud that is the most powerful accelerator of the Milky Way. So far, a complete mystery.
Video: High Altitude Water Cherenkov Experiment
https://www.youtube.com/watch?v=rW8l8LQt5d4
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