Dragonfly 44

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Dragonfly 44
Observation data
ConstellationComa Berenices
Right ascension 13h 00m 58.0s[1]
Declination+26° 58′ 35″[1]
Helio radial velocity6280 ± 120 km/s
Distance~100 Mpc (~330 Mly)
Group or clusterComa Cluster
Apparent magnitude (V)21 mag; or 19.4 mag [1]
Apparent magnitude (B)22
Absolute magnitude (V)-16.1 mag [1]
Mass~1.0×1012 M
Apparent size (V)10 x 35 arcsec
Other designations
SDSS J130057.98+265839.6, SDSS J130058.17+265836.1, SDSS J130058.21+265829.3

Dragonfly 44 is an ultra diffuse galaxy in the Coma Cluster.[2][3][1][4] Observations of the velocity dispersion suggest a mass of about one trillion solar masses, about the same as the mass of the Milky Way; the galaxy shows no evidence of rotation.[5] This is also consistent with about 90 globular clusters observed around Dragonfly 44. However, the galaxy emits only 1% of the light emitted by the Milky Way.[6] The galaxy was discovered with the Dragonfly Telephoto Array.[7]

To determine the amount of dark matter in this galaxy, they used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours over a period of six nights so they could determine the galaxy's mass. The scientists then used the Gemini Multi-Object Spectrograph on the 8-m Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy's core.[8]

In August 2016, astronomers reported that this galaxy might be made almost entirely of dark matter.[5][9][10]

See also[edit]


  1. ^ a b c d e Van Dokkum, Pieter; et al. (1 May 2015). "Spectroscopic confirmation of the existence of large, diffuse galaxies in the coma cluster". The Astrophysical Journal Letters. 804 (1): L26. arXiv:1504.03320. Bibcode:2015ApJ...804L..26V. doi:10.1088/2041-8205/804/1/L26.
  2. ^ "Scientists discover the fluffiest galaxies". phys.org. 14 May 2015.
  3. ^ Van Dokkum, Pieter; et al. (7 January 2015). "Forty-seven milky way-sized, extremely diffuse galaxies in the Coma-Cluster". The Astrophysical Journal Letters. 798 (2): L45. arXiv:1410.8141. Bibcode:2015ApJ...798L..45V. doi:10.1088/2041-8205/798/2/L45.
  4. ^ Dragonfly 44: Ultra-Diffuse Galaxy Made Mostly of Dark Matter. Aug 2016
  5. ^ a b Van Dokkum, Pieter; et al. (25 August 2016). "A High Stellar Velocity Dispersion and ~100 Globular Clusters For The Ultra-Diffuse Galaxy Dragonfly 44". The Astrophysical Journal Letters. 828 (1): L6. arXiv:1606.06291. Bibcode:2016ApJ...828L...6V. doi:10.3847/2041-8205/828/1/L6.
  6. ^ Crosswell, Ken (26 July 2016). "The Milky Way's dark twin revealed". Nature News. Retrieved 30 July 2016.
  7. ^ Rachel Feltman (25 August 2016). "A new class of galaxy has been discovered, one made almost entirely of dark matter". Washington Post.
  8. ^ http://earthsky.org/space/dragonfly-44-dark-matter-galaxy-2016
  9. ^ Hall, Shannon (25 August 2016). "Ghost galaxy is 99.99 per cent dark matter with almost no stars". New Scientist. Retrieved 27 August 2016.
  10. ^ Feltman, Rachael (26 August 2016). "A new class of galaxy has been discovered, one made almost entirely of dark matter". The Washington Post. Retrieved 26 August 2016.