Astronomers Identify a Galaxy Made Almost Entirely of Dark Matter
Arthur T Knackerbracket writes:
The galaxy is almost invisible, but its gravity gives it away:
While it is still considered a hypothetical theory, dark matter is being actively studied by scientists looking for novel cosmological clues. It does not interact with light or other types of electromagnetic radiation and can only be detected through its gravitational pull on nearby structures or the universe as a whole.
A team of astronomers led by David Li has recently confirmed the discovery of ten potential "dark galaxies," where starlight is so faint that it's extremely difficult to detect anything with traditional observatories. The new list also includes Candidate Dark Galaxy-2 (CDG-2), a celestial structure that might be composed of 99% dark matter and just 1% of normal matter.
CDG-2 was discovered by combining observations made through the Hubble Space Telescope, the Euclid space observatory, and the Hawaii-based Subaru Telescope. Li and his team at the University of Toronto were able to gain insight into the dark galaxy by looking for globular clusters, which are compact, spheroidal star formations that are closely bound together by gravity.
Thanks to Hubble's high-resolution cameras, the team was able to detect four different globular clusters in the Perseus galaxy cluster, 300 million light-years away from Earth. By combining further Euclid and Subaru observations, the researchers revealed a faint glow surrounding the clusters. This sparse light was coming from a nearby galaxy with extremely faint signs of starlight.
CDG-2 has a luminosity equivalent to one million Sun-like stars, with the four globular clusters making up 16% of its visible content. After using advanced statistical analysis, the astronomers speculate that 99% of all CDG-2's mass is just dark matter. Normal matter, including star-forming elements like hydrogen, was likely removed through gravitational interactions with nearby galaxies in the Perseus cluster.
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