One of the biggest mysteries in science is dark matter.
Image Credit: NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)
It is not visible since it does not reflect, absorb, or release light. However, the gravitational pull it seems to have on galaxies suggests its existence.
Although dark matter accounts for around 85 percent of the universe, scientists know nothing about its fundamental nature.
Theories
There are several theories, including research by Alex McDaniel, a postdoctoral scholar at Clemson University, that offer some of the stringent limits on the properties of dark matter.
Additionally, his study points to a faint indication of a signal that, if true, could be verified within the next ten or so.
With data collection and new discoveries in the future, this small hint could potentially turn into a very concrete detection of a dark matter model.
Alex McDaniel, Postdoctoral Researcher, Clemson University
Finding dark matter would be revolutionary.
Dark matter is one of the most important things in astrophysics, and we know next to nothing about it. Discovering it will be a tremendous breakthrough. Whoever discovers may win a Nobel Prize. It is that big.
Marco Ajello, Associate Professor, Department of Physics and Astronomy, Clemson University
Dwarf Galaxies
In this study, McDaniel and colleagues looked for dwarf galaxies that contain dark matter, which self-annihilates into ordinary matter and gamma rays, the most energetic type of light. Dwarf galaxies are suitable for study because they are tiny, dense in dark matter, and lack other astrophysical phenomena like gas, dust, and supernovae that might corrupt the results.
McDaniel added, “We look for these because, ideally, they give us a clean signal or allow us to rule out certain particle theories.”
Some theories suggest that dark matter has a definite mass or cross section, which represents the chance of a specific event occurring as a result of particle interaction. That would dictate what researchers are likely to find in gamma rays. If they fail to see that, McDaniel continued, they can exclude such masses and cross sections.
Ruling Out
In this paper, we do more ruling out, saying that dark matter can’t have those masses or cross section. But compared to previous studies, we do start to see a hint of something that might be a signal from these systems.
Chris Karwin, Study Co-Author and Postdoctoral Fellow, NASA Goddard Space Flight Center
McDaniel’s study makes use of bigger samples, including additional discovered dwarf galaxies, as well as more data than earlier studies. He included roughly 50 dwarf galaxies in his analysis, but he expects the number to rise to 150–200 when new, more powerful telescopes become available in the near future.
“The new telescopes are basically dwarf galaxy detectors. We are projecting with those improvements it’s possible that instead of having just a little hint of a signal, we can have something that’s a bona fide detection,” McDaniel added.
Ajello concluded, “If it (the signal) is real, eventually it will be confirmed.”
Journal Reference:
McDaniel, A., et. al. (2024) Legacy analysis of dark matter annihilation from the Milky Way dwarf spheroidal galaxies with 14 years of Fermi-LAT data. Physical Review D. doi:10.1103/PhysRevD.109.063024