Cloud-9 (RELHIC)

Cloud-9
Image of region around Cloud-9 from Hubble Space Telescope's advanced camera system, overlaid with radio emission data from the Very Large Array, which shows the extent of the cloud in magenta. The circle shows the central region searched for stars
Observation data (J2000 epoch)
ConstellationUrsa Major[1]
Right ascension12h 51m 51.33s[1]
Declination+40° 18′ 05.46″[1]
Distance14 Mly[1]
Characteristics
TypeRELHIC
Other designations
  • Cloud-9

Cloud-9 is a Reionization-Limited HI Cloud (RELHIC), and possibly a starless dark matter galaxy.[2][3][4] This RELHIC may have a total mass of 5 billion times that of the Sun and was found in the vicinity of the spiral galaxy Messier 94 (M94), in the constellation Canes Venatici.[5][6]

Discovery

CL-9's observed column density isocontours (taken from Z23)

Cloud-9 was initially detected as a compact H I cloud during radio observations with Five-hundred-meter Aperture Spherical Telescope (FAST) in 2023 as part of a survey of the northern sky and confirmed by NASA's Hubble Space Telescope in early 2026, Cloud-9 is the first confirmed example of a failed galaxy[7][8] of a type predicted by the Lambda CDM cold dark matter cosmological model, having captured hydrogen gas but failed to initiate star formation.[3][6] It was catalogued as the ninth such cloud identified on the outskirts of the nearby spiral galaxy M94, leading to its name.[3] Independent confirmation of the H I detection came from follow-up observations with the Very Large Array (VLA) and the Robert C. Byrd Green Bank Telescope (GBT).[6]

See also

References

  1. 1 2 3 4 "Cloud 9, Starless Gas Cloud - NASA Science". 2026-01-05. Retrieved 2026-04-17.
  2. ↑ Benitez-Llambay, Alejandro; Navarro, Julio F. (September 2023), "Is a Recently Discovered H I Cloud near M94 a Starless Dark Matter Halo?", The Astrophysical Journal, 956 (1): 1, arXiv:2309.03253, Bibcode:2023ApJ...956....1B, doi:10.3847/1538-4357/acf767, ISSN 0004-637X
  3. 1 2 3 "NASA's Hubble Examines Cloud-9, First of New Type of Object - NASA Science". 2026-01-05. Retrieved 2026-04-17.
  4. ↑ Cloud-9: a new celestial object found by Hubble, European Space Agency, retrieved 2026-01-09
  5. ↑ "Astronomers may have found a galaxy that's all dark matter, with no stars", Sky at Night, BBC, 2 November 2023, retrieved 2024-01-22
  6. 1 2 3 Anand, Gagandeep S.; Benítez-Llambay, Alejandro; Beaton, Rachael; Fox, Andrew J.; Navarro, Julio F.; D’Onghia, Elena (2025-11-10). "The First RELHIC? Cloud-9 is a Starless Gas Cloud *". The Astrophysical Journal Letters. 993 (2): L55. arXiv:2508.20157. Bibcode:2025ApJ...993L..55A. doi:10.3847/2041-8213/ae1584. ISSN 2041-8205.
  7. ↑ iain.todd@ourmedia.co.uk (2026-01-07), "Scientists have found a new kind of object in deep space. And it could help solve one of the Universe's biggest mysteries", Sky at Night, BBC
  8. ↑ Ahart, Jenna, "Do All Galaxies Need Stars? Astronomers Discover a New Class of Astronomical Object", Scientific American
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