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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: 1) by khallow on Friday February 02 2024, @04:16PM (3 children)
Except? That would be non-luminous matter in a nutshell. You have to look indirectly. I understand gravitational lensing shows something is going on.
(Score: 2) by Immerman on Friday February 02 2024, @05:04PM (2 children)
Look at your hand - it's non-lumnous matter, yet you can still see it.
Pitch black night so you can't actually see your hand directly? Hold it up to the stars, and you can still see its outline by the stars that it obscures. And that's true of ALL luminous matter. Even glass is completely opaque across much of the EM spectrum.
And yet when we look at where we know dark matter must be, we see neither. So we know whatever is there (if there's really something there), it doesn't interact with light. Which rules out anything made of atoms.
(Score: 2) by Immerman on Friday February 02 2024, @05:17PM
Sorry, that should be:
And that's true of ALL normal matter.
not luminous
(Score: 1) by khallow on Saturday February 03 2024, @06:15AM
Only because it's near my face. If it were 50k light-years away at the edge of the Milky Way, I wouldn't see it that way, even if there were several million solar mass of them out there. At that point, you'd have to look for indirect effects like occultation or gravitational lensing.
The problem then is that a dense object like a hand doesn't occult much for its mass. Nebula are extremely puffy - Wikipedia states a typical nebula cloud the size of Earth would weigh a few kilograms. That's a few hands of mass. And illuminate that nebula with ionizing uv or x-rays and suddenly you have an object much brighter than its equivalent in hands would be.
We do see gravitational lensing.