- 4071 - NEUTRINOS - discovered by IceCube Observatory. The first 'ghost particle' image of Milky Way galaxy are neutrinos detected by IceCube. Our Milky Way galaxy is an awe-inspiring feature of the night sky, viewable with the naked eye as a horizon-to-horizon hazy band of stars. Now, for the first time, the IceCube Neutrino Observatory has produced an image of the Milky Way using “neutrinos”, tiny, ghostlike astronomical messengers, but not photons.
----------- 4071 - NEUTRINOS - discovered by IceCube Observatory
- The high-energy
neutrinos, with energies millions to billions of times higher than those
produced by the fusion reactions that power stars, were detected by the IceCube
Neutrino Observatory, a gigaton detector operating at the Amundsen-Scott South
Pole Station.
-
- This one-of-a-kind
detector encompasses a cubic kilometer of deep Antarctic ice instrumented with
over 5,000 light sensors. IceCube searches for signs of high-energy neutrinos
originating from our galaxy and beyond, out to the farthest reaches of the
universe.
-
- Unlike the case
for light of any wavelength, in neutrinos, the universe outshines the nearby
sources in our own galaxy. The
capabilities provided by the highly sensitive IceCube detector, coupled with
new data analysis tools, have given astronomers an entirely new view of our
galaxy.
-
- Interactions
between cosmic rays, high-energy protons and heavier nuclei, also produced in
our galaxy, and galactic gas and dust inevitably produce both gamma rays and
neutrinos. Given the observation of gamma rays from the galactic plane, the
Milky Way was expected to be a source of high-energy neutrinos.
-
- The search focused
on the southern sky, where the bulk of neutrino emission from the galactic
plane is expected near the center of our galaxy. However, until now, the
background of muons and neutrinos produced by cosmic-ray interactions with the
Earth's atmosphere posed significant challenges.
-
- To overcome these
challenges, IceCube developed analyses that select for "cascade"
events, or neutrino interactions in the ice that result in roughly spherical
showers of light. Because the deposited energy from cascade events starts
within the instrumented volume, contamination of atmospheric muons and
neutrinos is reduced. Ultimately, the higher purity of the cascade events gave
a better sensitivity to astrophysical neutrinos from the southern sky.
-
- However, the final
breakthrough came from the implementation of machine learning methods,
developed by IceCube collaborators at TU Dortmund University, that improve the
identification of cascades produced by neutrinos as well as their direction and
energy reconstruction.
-
- The improved
methods allowed astronomers to retain over an order of magnitude more neutrino
events with better angular reconstruction, resulting in an analysis that is
three times more sensitive than the previous search.
-
- The dataset used
in the study included 60,000 neutrinos spanning 10 years of IceCube data, 30
times as many events as the selection used in a previous analysis of the
galactic plane using cascade events. These neutrinos were compared to
previously published prediction maps of locations in the sky where the galaxy
was expected to shine in neutrinos.
-
- The maps
included one made from extrapolating Fermi Large Area Telescope gamma-ray
observations of the Milky Way and two alternative maps identified as KRA-gamma
by the group of theorists who produced them. The power of machine learning
offers great future potential, bringing other observations closer within reach.
-
- Observing our own
galaxy for the first time using particles instead of light is a huge step. As neutrino astronomy evolves, we will get a
new lens with which to observe the universe.
-
June 29, 2023 NEUTRINOS -
discovered by IceCube Observatory 4071
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Friday, June 30, 2023
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