Astronomers have discovered an unusual galaxy named Candidate Dark Galaxy-2 (CDG-2), located about 300 million light-years away, characterized by an extreme lack of visible stars. It is estimated that 99.9% of its mass is composed of dark matter, with only 0.1% being conventional material. The galaxy is nearly invisible, with only four globular clusters contributing to its brightness.
A recent study published in The Astrophysical Journal Letters utilized data from the Hubble, Euclid, and Subaru telescopes, revealing a faint glow around these clusters, indicating the presence of an underlying galaxy. CDG-2’s total luminosity is estimated at about 6 million Suns, with the globular clusters accounting for 16% of its brightness. This distribution implies that CDG-2 is a gravitationally bound system with a dense dark matter halo.
Dark matter constitutes approximately 27% of the universe’s total energy density and 85% of its matter, although its exact nature remains unknown. CDG-2 exemplifies extreme cases of “dark galaxies,” which are valuable for studying dark matter and testing galaxy formation models.
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