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from the noone-knows-how-the-cloud-works dept.
A nearly invisible dwarf galaxy is challenging the model of dark matter. An international team of astronomers, led by the Instituto de Astrofísica de Canarias (IAC) in collaboration with the University of La Laguna (ULL) and other institutions, discovered this fascinating galaxy dubbed "Nube."
Nube, which means "Cloud" in Spanish, was named by the 5-year-old daughter of one of the researchers, aptly reflecting the galaxy's ghostly and diffuse appearance. Its discovery is significant because its faint surface brightness allowed it to remain undetected in previous sky surveys, despite its considerable size.
"With our present knowledge we do not understand how a galaxy with such extreme characteristics can exist," says study first author Mireia Montes, researcher at the IAC and the ULL, in a media release.
Nube is unique in its properties, being ten times fainter yet ten times more extended than other dwarf galaxies with a similar number of stars. Its discovery is akin to finding a hidden treasure in a well-explored attic. Nube is large and yet faint, a ghostly apparition in the universe. To put it into perspective, it's about one-third the size of the Milky Way but has a mass comparable to the Small Magellanic Cloud.
What sets it apart is its significant amount of dark matter, an invisible substance that does not emit, absorb, or reflect light, making it undetectable by traditional telescopes.
Related: Bizarre Galaxy Discovered With Seemingly No Stars Whatsoever
(Score: 2) by Immerman on Friday February 02 2024, @05:07PM (1 child)
Right, so any neutrinos that existed at that time would be hot, and matter has been two diffuse since the CMBR for them to shed much of that heat.
(Score: 1) by khallow on Saturday February 03 2024, @06:29AM
Unless, of course, that velocity was shed. The paper I linked back some ways had a mechanism - interaction with strong magnetic fields.
And there would be additional velocity loss from red shift. For example, from the most distant galaxies, one gets red shifts of over 10. What that means is that light traveling from that galaxy loses a factor of ten or more energy in its travel to us. A typical near light-speed neutrino taking the same route would lose a similar amount of energy. Neutrinos from the initial moments of the Big Bang would lose much more energy due to much higher red shifts - we're talking orders of magnitude loss. If they start with initial extremely high energy, then they can stay hot and extremely fast even now. But if they don't, then they can well slow down enough by now that they can be caught by galaxies.
That's the theoretical mechanism for cold neutrino creation and capture.