“There are many low mass galaxies which are dominated by dark matter, but for most normal galaxies like the Milky Way, normal stars dominate in the inner parts and dark matter is prominent in the “halo” surrounding the system”, he told FoxNews.com in an email.
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Powerful telescopes have revealed that a nearby galaxy is 99.99 percent dark matter.
The hazy oval isn’t glare on your screen; it’s an entire galaxy.
However, an worldwide team of astronomers spotted it a year ago using the WM Keck Observatory and the Gemini North Telescope in Manuakea, Hawaii, when the Dragonfly Telephoto Array observed a region of the sky in the constellation Coma.
But those galaxies were roughly 10,000 times less massive than Dragonfly 44. It was discovered just previous year when the Dragonfly Telephoto Array observed a region of the sky in the constellation Coma.
“We planned to study the outskirts of galaxies to see what exists around them, but by accident we saw all these little smudges”, study author Pieter van Dokkum of Yale told The Post. Image Credit: Pieter van Dokkum, Roberto Abraham, Gemini Observatory/AURA. “This finding opens up a whole new class of massive objects that we can study”. The mass-to-light ratio is M/L=48 M_sun/L_sun, and the dark matter fraction is 98 percent within the half-light radius.
Scientists have gone back and forth on the nature of dark matter: It could take the form of massive astrophysical compact halo objects, or MACHOs.
Scientists know that there must be something providing the gravity that is needed to hold the galaxy together.
Dragonfly 44 wasn’t like the dark galaxies that have been found before, which are all quite tiny. These galaxies are the same size and shape of regular galaxies, but contain far fewer stars. Ultra-faint dwarf galaxies have similar compositions.
Star velocities are an indication of the galaxy’s mass, the researchers noted. What they found shocked them.
“It’s pretty insane, the difference from the Milky Way is a factor of 100”. It’s as if someone picked through the Milky Way, selecting just one star out of 100 and throwing the rest away.
“They are found in a dense, violent region of space filled with dark matter and galaxies whizzing around, so we think they must be cloaked in their own invisible dark matter “shields” that are protecting them from this intergalactic assault”. “That’s just something we never knew could happen”. Dragonfly 44 is very faint for its mass and consists nearly entirely of dark matter.
“We have no idea how galaxies like Dragonfly 44 could have formed”, said Abraham.
They said that there may be many more of the odd, ghost galaxies waiting to be found.
‘Ultimately what we really want to learn is what dark matter is.
Galaxies the size of Dragonfly 44 and the Milky Way usually have all the right ingredients for widespread star formation.
Van Dokkum and his colleagues were not looking for a dark galaxy. Especially in the dense Coma Cluster, the gravitational pull of other galaxies would tear them apart. If it were close enough to study, a galaxy that is nearly totally dark might be quiet enough for scientists to pick out the first direct evidence of dark matter.
The researchers are searching the sky now.
“By pulling them all together into this array, which makes them look like the eyes of an insect, we gather a lot more light”, says van Dokkum. “It’s not some weird singular galaxy that’s just a curiosity”.
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Dark matter remains perhaps the biggest mystery of the universe.
