Far out cosmology: tracking Milky Way neutrinos (Introduction)

by David Turell , Friday, June 30, 2023, 17:14 (302 days ago) @ David Turell

A new discovery:

https://www.sciencenews.org/article/neutrinos-new-view-milky-way-space

"Scientists have made the first image of the Milky Way using neutrinos.

"The extremely low-mass subatomic particles have no electric charge, and pass easily through gas, dust and even stars on their way from the places where they originate to detectors here on Earth. High-energy neutrinos zip throughout the cosmos, but where they come from is usually a mystery.

"Now, by combining artificial intelligence and data collected over the course of a decade with the IceCube detector in Antarctica, researchers have found the first evidence of high-energy neutrinos that originated from inside the Milky Way and mapped the particles onto an image of the galaxy’s plane. It’s the first time our galaxy has been imaged with anything other than light.

"The map includes suggestions of specific high-energy neutrino sources within the Milky Way that might be the remnants of past supernova star explosions, the cores of collapsed supergiant stars or other as-yet-unidentified objects, the team reports in the June 30 Science. But more research is needed to clearly pick those sorts of features out of the data.

"Previously, only a few high-energy neutrinos have been traced back to their potential birthplaces, all outside the Milky Way. Those include two that appeared to come from black holes shredding their companion stars and others from a highly active galaxy known as a blazar.

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"Neutrino astronomy could potentially allow us to see distant objects in a way that no other telescopes can match. That’s because neutrinos can cross huge expanses of space without being absorbed or deflected. X-rays, gamma rays, optical light and the charged particles that make up cosmic rays, on the other hand, can be deflected or absorbed along the way, which may obscure their origins.

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"The downside of neutrinos is that they’re extremely hard to detect. The IceCube experiment is enormous in part to overcome that challenge. It consists of 5,160 sensors in a cubic array one kilometer on a side embedded deep in the Antarctic ice. The large size of the experiment increases the odds of seeing a tiny fraction of the neutrinos flying through space from the Milky Way and other places in the cosmos.

"Of the 100,000 or so neutrinos that IceCube scientists observe each year, some leave long tracks in the detector that potentially point back to where the neutrinos came from. Many of the neutrino signals in IceCube, though, are known as cascade events. They make bursts of light in the detector, but don’t reveal neutrino origins as well as tracks can.

“'This is data we used to throw away in terms of astronomy,” Kurahashi Neilson says. There’s still information indicating where the neutrinos come from in the data. But it’s difficult to identify the promising cascades in the hundreds of thousands of meaningless, background events that IceCube has collected."

Comment: paradoxically, this massless particle may help to explain why the universe is so big, a crushing worry from dhw.