Dark galaxy

A dark galaxy are hypothetical galaxies that is made up with dark matter but with almost no stars. They have this name because they have no visible stars but may be detectable if they have a huge amount of gas. Dark galaxies are different from intergalactic gas clouds. Distinguishing between intergalactic gas clouds and dark galaxies is difficult. The best candidate dark galaxies as of 2025 include HI1225+01, AGC229385, AC G185.0-11.5 and others.

Size

The actual size of dark galaxies is not known because they cannot be seen with normal telescopes. Some estimations say that these dark galaxies are double the size of Milky Way to the size of a small quasar.

Structure

Dark galaxies are theoretically composed of dark matter, hydrogen and cosmic dust. Some scientist support the idea that dark galaxies could contain stars. But the exact composition of dark galaxies remains not known. Some astronomers believe that the mass of the gas in the dark galaxies is approximately one billion solar masses.

Possible dark galaxies

FAST J0139+4328

Located 94 million light years away from Earth, this galaxy is visible in radio waves in tiny amount of visible light.

References

  1. ↑ "The Arecibo Legacy Fast ALFA Survey". egg.astro.cornell.edu. Retrieved 2026-03-13.
  2. ↑ "First direct detection sheds light on dark galaxies". ScienceDaily. Retrieved 2026-03-13.
  3. ↑ Starr, Michelle (2023-02-10). "Mysterious Dark Galaxy Emits No Visible Light, Scientists Say". ScienceAlert. Retrieved 2026-03-13.