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The observation is ground-breaking and established the galaxy as a neutrino source, a research spokesperson said
Published : 03 Jul 2023, 01:41 PM
Human beings for millennia have gazed with awe at the vast torrent of stars - bright and dim - shining in Earth's night sky that comprise theMilky Way.Ourhomegalaxy, however, is now beingobserved for the first time in a brandnewway.
Scientistssaid on Thursday they have produced an image of the Milky Way not based on electromagnetic radiation - light - but on ghostly subatomic particles calledneutrinos. They detected high-energyneutrinosin pristine ice deep below Antarctica's surface, then traced their source back to locations in the Milky Way - the first time these particles have beenobserved arising fromourgalaxy.
This view differs fundamentally from what we can see withourown eyes or with instruments that measure other electromagnetic sources like radio waves, microwaves, infrared, ultraviolet, X-rays and gamma-rays. It is not stars and planets and other stuff observable thanks to their light, but rather the mysterious sources ofneutrinosoriginating in thegalaxy, perhaps remnants of explosive star deaths called supernovas.
Theneutrinoswere detected over a span of a decade at the IceCube Neutrino Observatory at a US scientific research station at the South Pole, using more than 5,000 sensors covering an area the size of a small mountain.
"This observation is ground-breaking. It established thegalaxyas a neutrino source. Every future work will refer to this observation," said Georgia Tech physicist Ignacio Taboada, spokesperson for the IceCube research.
"When we discoveredneutrinosof cosmic origin in 2013, it was somewhat of a surprise to us that we did not find a flux that originated in the nearby sources ofourowngalaxy. Galactic sources were supposed to dominate the sky, as they do in all wavelengths of light. It took us a decade to discoverourowngalaxy," said University of Wisconsin physicist and IceCube lead scientist Francis Halzen.
Neutrinosare electrically neutral, undisturbed by even the strongest magnetic field, and rarely interact with matter, earning the nickname "ghost particle." Asneutrinostravel through space, they pass unimpeded through matter - stars, planets and, for that matter, people.
"Just as light goes without stopping through glass,neutrinoscan go through everything, including thewholeplanet Earth," Taboada said.
"The neutrino is an elementary particle, meaning they are not made up of anything smaller. They are not the building blocks of 'stuff,' like electrons and quarks are, but they are created in nuclear processes. They are also created when protons (subatomic particles) and (atomic) nuclei interact at very high energies," said physicist Naoko Kurahashi Neilson of Drexel University in Philadelphia, a member of the research team that detailed the findings in the journalScience.
Many aspects of the universe are indecipherable using light alone. The ability to use particles likeneutrinosin astronomy enables a more robust examination, much as the confirmation of ripples in the fabric of space-time calledgravitational waves, announced in 2016, opened anothernewfrontier. This field is called "multi-messenger astrophysics."
Neutrinosare produced by the same sources as cosmic rays, the highest-energy particles everobserved, but differ in a key respect. Cosmic rays, as electrically charged particles, cannot be traced straight back to their source because strong magnetic fields in space alter their trajectory. The direction from whichneutrinosarrive points directly back to their original source.
The researchers harnessed machine learning to help distinguish neutrinos originating inourgalaxyfrom those originating elsewhere. They released an illustration of their findings withneutrinosfrom the Milky Way represented by light, with a heavy concentration at thegalaxy's core.
How theneutrinosoriginated is a matter of debate. The observations were consistent with the idea of a diffuse emission ofneutrinosin the MilkyWay,but these particles could arise from specific yet-unknown sources.
"This is now the key question.Neutrinosonly originate in sources where cosmic rays are produced. They are tracers of cosmic ray sources. The key question is where these cosmic rays originate," Halzen said.
"The most likely source ofneutrinosand cosmic rays inourgalaxy," Taboada added, "are the remains of past supernova explosions. But this is unproven so far."
