First 'ghost particle' image of Milky Way
Elusive neutrinos reveal a portrait of our galaxy unlike any before

Date:
June 29, 2023
Source:
National Science Foundation
Summary:
Scientists have revealed a uniquely different image of our galaxy
by determining the galactic origin of thousands of neutrinos --
invisible 'ghost particles' which exist in great quantities but
normally pass straight through Earth undetected. The neutrino-based
image of the Milky Way is the first of its kind: a galactic portrait
made with particles of matter rather than electromagnetic energy.


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FULL STORY ==========================================================================
From visible starlight to radio waves, the Milky Way galaxy has long been observed through the various frequencies of electromagnetic radiation
it emits.

Scientists have now revealed a uniquely different image of our galaxy by determining the galactic origin of thousands of neutrinos -- invisible
"ghost particles" which exist in great quantities but normally pass
straight through Earth undetected. The neutrino-based image of the Milky
Way is the first of its kind: a galactic portrait made with particles
of matter rather than electromagnetic energy.

The breakthrough was achieved by a collaboration of researchers using
the U.S.

National Science Foundation-supported IceCube Neutrino Observatory at
NSF's Amundsen-Scott South Pole Station in Antarctica. The immense
observatory detects the subtle signs of high-energy neutrinos from
space by using thousands of networked sensors buried deep within a
cubic kilometer of clear, pristine ice. The results were revealed at an
event today at Drexel University and will be published tomorrow in the
journal Science.

"I remember saying, 'At this point in human history, we're the first
ones to see our galaxy in anything other than light,'" says Drexel
University physicist Naoko Kurahashi Neilson of the moment she and two
doctoral students, Steve Sclafani with Drexel and Mirco Hu"nnefeld with
TU Dortmund University in Germany, first examined the image. Kurahashi
Neilson proposed the innovative computational analysis used to generate
the image and received funding to pursue her idea through a grant from
NSF's Faculty Early Career Development program.

"As is so often the case, significant breakthroughs in science are
enabled by advances in technology," says Denise Caldwell, director
of NSF's Physics Division. "The capabilities provided by the highly
sensitive IceCube detector, coupled with new data analysis tools,
have given us an entirely new view of our galaxy -- one that had only
been hinted at before. As these capabilities continue to be refined, we
can look forward to watching this picture emerge with ever-increasing resolution, potentially revealing hidden features of our galaxy never
before seen by humanity." "What's intriguing is that, unlike the case
for light of any wavelength, in neutrinos, the universe outshines the
nearby sources in our own galaxy," says Francis Halzen, a physicist at
the University of Wisconsin-Madison and principal investigator at IceCube.

Beyond the daunting challenge of just detecting notoriously elusive
neutrinos (and distinguishing them from other sorts of interstellar
particles) is the even more ambitious goal of determining where they came
from. When neutrinos happen to interact with the ice beneath IceCube,
those rare encounters produce faint patterns of light, which IceCube can detect. Some patterns of light are highly directional and point clearly
to a particular area of the sky, allowing researchers to determine the
source of the neutrinos. Such interactions were the basis for the IceCube Collaboration's 2022 discovery of neutrinos that came from another galaxy
47 million light-years away.

Other interactions are far less directional and produce cascading "fuzz
balls of light" in the clear ice, says Kurahashi Neilson. Her fellow
IceCube Collaboration members, Sclafani and Hu"nnefeld, developed a machine-learning algorithm that compared the relative position, size
and energy of more than 60,000 such neutrino-generated cascades of light recorded by IceCube over 10 years.

The three researchers spent over two years meticulously testing and
verifying their algorithm using artificial data simulating neutrino
detections. When they eventually fed the real IceCube-provided data to the algorithm, what emerged was a picture showing bright spots corresponding
to locations in the Milky Way that were suspected to emit neutrinos. Those locations were in places where observed gamma rays were thought to be
the byproducts of collisions between cosmic rays and interstellar gas,
which theoretically should also produce neutrinos.

"A neutrino counterpart has now been measured, thus confirming what we
know about our galaxy and cosmic ray sources," says Sclafani.

Over many decades, scientists have revealed countless astronomical
discoveries by expanding the methods used to observe the
universe. Once-revolutionary advances such as radio astronomy and infrared astronomy have been joined by a new class of observational techniques
using phenomena such as gravitational waves and now, neutrinos. Kurahashi Neilson says that the neutrino-based image of the Milky Way is yet another
step in that lineage of discovery. She predicts neutrino astronomy will
be honed like the methods that preceded it, until it too can reveal
previously unknown aspects of the universe.

"This is why we do what we do," she says. "To see something nobody has
ever seen, and to understand things we haven't understood."
* RELATED_TOPICS
o Space_&_Time
# Galaxies # Astronomy # Astrophysics # Cosmic_Rays #
Space_Telescopes # Cosmology # Space_Exploration #
Black_Holes
* RELATED_TERMS
o Milky_Way o Neutrino o Subatomic_particle o Globular_cluster
o Dark_matter o Interstellar_medium o Magellanic_Clouds o
Hubble_Deep_Field

========================================================================== Story Source: Materials provided by National_Science_Foundation. Original written by Jason Stoughton. Note: Content may be edited for style
and length.


========================================================================== Related Multimedia:
* A_composite_image_of_an_optical_view_of_the_Milky_Way_along_with_the
first-ever_neutrino-based_image_of_the_Milky_Way ========================================================================== Journal Reference:
1. R. Abbasi et al. Observation of high-energy neutrinos from the
Galactic
plane. Science, 2023; 380 (6652): 1338 DOI: 10.1126/science.adc9818 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230629193240.htm

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