The Milky Way shines in the new ghost particle neutrino image

Milky Way: long white and blue cloud-like formation on a black background.
View larger. | This is a composite image of the Milky Way. Combine a visible light image with the new neutrino image. Here, the neutrino regions appear blue. Image via IceCube Collaboration/ US National Science Foundation (Lily Le & Shawn Johnson) /ESO (S. Brunier).

We’ve all seen photos of our own galaxy, the Milky Way, as a beautiful band of stars stretching across the night sky. In addition to views of the Milky Way in visible light, astronomers have shown us our home galaxy in other wavelengths of the spectrum, from radio waves to gamma rays. On June 29, 2023, a team of researchers using the IceCube Neutrino Observatory in Antarctica released a new image of the Milky Way… a view never seen until now. It is the first image of our galaxy in anything other than electromagnetic radiation. This image captures the galaxy with neutrinos, o ghost particles.

The National Science Foundation (NSF) supports IceCube, which is located at the AmundsenScott South Pole Station in Antarctica.

The researchers published the peer-reviewed findings in Science on June 29, 2023.

Observing the Milky Way with neutrinos

This is the first time anyone has imaged our galaxy using neutrinos, also known as ghost particles. Physicist Naoko Kurahashi Neilson of Drexel University in Philadelphia said:

I remember saying, “At this point in human history, we are the first to see our galaxy in anything other than light.”

Neilson, Steve Sclafani of Drexel and Mirco Hnnefeld of TU Dortmund University in Germany were the first to study the new image.

The bright spots in the image are places in the Milky Way where neutrinos are emitted. Those locations just happen to be in locations where gamma rays are thought to be the byproducts of collisions between cosmic rays and interstellar gas. These collisions should theoretically produce neutrinos. Sclafani said:

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

Furthermore, the bright spots also differ from the wavelengths of visible light. Francis Halzen, a physicist at the University of Wisconsin at Madison and principal investigator of IceCube, said:

What’s interesting is that, unlike light of any wavelength, in neutrinos, the universe outshines nearby sources in our galaxy.

Long rectangle with dark cloud-like star formation and long rectangle underneath with bright bluish spots.
View larger. | These 2 images compare the visible light view of the Milky Way (top) with the neutrino view below). Image via IceCube Collaboration/ US National Science Foundation (Lily Le & Shawn Johnson)/ ESO (S. Brunier).

Tracing the origins of neutrinos

The search for neutrinos has focused on the southern sky. From the southern sky it is easier to see the galactic plane which is near the center of our galaxy. This is the region where astronomers believe most of the neutrino emissions come from.

By nature, neutrinos are difficult to detect. And, with that in mind, researchers want to know where they come from. Neutrinos rarely interact with the ice under IceCube in Antarctica, but when they do, they produce faint patterns of light. Some of them indicate specific areas of the sky. So by following the path they took, astronomers can tell where they originated from. For example, in 2022, IceCube detected neutrinos from a galaxy 47 million light years away.

Other models, however, are less clear. They’re less directional and tend to produce what astronomers call “fuzzy balls of light.” Overall, IceCube has detected over 60,000 of these cascading “fuzz balls” over the past 10 years. That’s 30 times more than in a previous analysis of the galactic plane using cascade events.

More specifically, these “cascade events are neutrino interactions in ice that result in roughly spherical showers of light.

Also, neutrinos may be tiny, but they do contain a lot of energy millions to billions times higher than those produced by fusion reactions. It’s those reactions that fuel the stars.

Ignacio Taboada, a physics professor at the Georgia Institute of Technology, said:

Strong evidence that the Milky Way is a source of high-energy neutrinos survived rigorous testing of the collaboration. Now the next step is to identify specific sources within the galaxy.

Colored band crossing the night sky, with a large building and cylindrical tower below.
View larger. | This composite photo shows the neutrino-based image of the Milky Way and the IceCube Neutrino Observatory in Antarctica. Image via IceCube Collaboration (Yuya Makino)/ US National Science Foundation.

Technological advances

IceCube is extremely sensitive and represents the latest neutrino detection technology. It detects the subtle signals of high-energy neutrinos from space using more than 5,000 networked light sensors buried deep within 0.2 cubic miles (0.8 cubic km) of pristine ice. As Denise Caldwell, director of the physics division at the National Science Foundation, noted:

As is often the case, significant advances in science are made possible by advances in technology. The capabilities provided by the highly sensitive IceCube detector, together 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 look forward to seeing this image emerge in ever-increasing resolution, potentially revealing hidden features of our galaxy never before seen by mankind.

As Hnnefeld also noted:

The improved methods allowed us to retain over an order of magnitude more neutrino events with improved angular reconstruction, resulting in an analysis three times more sensitive than previous research.

And this is only the beginning. Neilson thinks the use of neutrinos in astronomy will lead to further discoveries. And that’s the essence of science, he said:

This is why we do what we do. Seeing something no one has ever seen and understanding things we didn’t understand.

She added:

As neutrino astronomy evolves, we will have a new lens with which to observe the universe.

Bottom line: Scientists have released a new image of ‘ghost particles’ of the Milky Way. It’s the first image ever taken of our home galaxy using neutrinos instead of visible light.

Source: Observation of high-energy neutrinos from the galactic plane

Through the National Science Foundation

IceCube neutrino observatory

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Image Source : earthsky.org

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