Astronomical objects

physical body of astronomically-significant size, mass, or role, naturally occurring in a universe

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unexplained circular astronomical object detected only by radio waves

group of early-class stars weakly gravitationally bounded

Celestial coordinate system

Candidate Dark Galaxy 2 (CDG-2) is a candidate for a dark galaxy, composed predominantly of dark matter, along with four globular clusters, in the Perseus cluster. It'd be one of the most dark matter dominated galaxies probably detected, estimated to be between 99.94% and 99.98% dark matter. It has been not confirmed yet if it's a true dark galaxy, more studies are required for a definitive conclusion.