# Dragonfly 44

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Galaxy in constellation Coma Berenices

Dragonfly 44 Hubble Space Telescope view of the galaxy Dragonfly 44 Observation data (J2000 epoch) Constellation Coma Berenices Right ascension 13h 00m 58.0s[1] Declination +26° 58′ 35″[1] Redshift ~0.023 Heliocentric radial velocity 6280 ± 120 km/s Distance ~100 Mpc (~330 Mly) Group or cluster Coma Cluster Apparent magnitude (V) 21 mags; or 19.4 mags[2] Apparent magnitude (B) 22 Absolute magnitude (V) -16.1 mag[2] Characteristics Mass ~1.6×1011 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](/source/Ultra_diffuse_galaxy) in the [Coma Cluster](/source/Coma_Cluster).[1][3][2][4] This galaxy is well-known because observations of the [velocity dispersion](/source/Velocity_dispersion) in 2016 suggested a mass of about one trillion [solar masses](/source/Solar_mass), about the same as the [Milky Way](/source/Milky_Way). This mass was consistent with a count of about 90 and 70 [globular clusters](/source/Globular_clusters) observed around Dragonfly 44 in two different studies.

Later, spatially resolved [kinematics](/source/Kinematics) measured a mass of about 160 billion [solar masses](/source/Solar_mass), six times less than early mass measurements and one order of magnitude less than the [Milky Way's](/source/Milky_Way) mass.[5] The most recent work found 20 [globular clusters](/source/Globular_cluster) around the galaxy, which is consistent with the current mass measurement.[6][7] The lack of [X-ray](/source/X-ray) emission from the galaxy and its surroundings also shows that the number of [globular clusters](/source/Globular_cluster) cannot be as many as was claimed before.[8]

The galaxy emits only 1% of the light emitted by the Milky Way.[9] The galaxy was discovered with the [Dragonfly Telephoto Array](/source/Dragonfly_Telephoto_Array).[10]

## Early study

To determine the amount of [dark matter](/source/Dark_matter) in this galaxy, in 2016, astronomers used the DEIMOS instrument installed on [Keck II](/source/Keck_II) to measure the velocities of stars for 33.5 hours for 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](/source/Gemini_North) telescope to reveal a halo of spherical clusters of stars around the galaxy's core.[11] Following this observation, in August 2016, astronomers reported that this galaxy might be [made almost entirely](/source/Dark_galaxy) of dark matter.[12][13][14]

## See also

- [Globular cluster](/source/Globular_cluster) – Spherical collection of stars

- [Low surface brightness galaxy](/source/Low_surface_brightness_galaxy) – Galaxy which is less bright than the ambient night sky (LSB galaxy)

- [NGC 1052-DF2](/source/NGC_1052-DF2) – Ultra diffuse galaxy in the constellation Cetus – a galaxy thought to contain almost no dark matter.

- [Type-cD galaxy](/source/Type-cD_galaxy) – Galaxy morphology classification or *c-Diffuse* galaxy type

- [Type-D galaxy](/source/Type-D_galaxy) – System for categorizing galaxies based on appearancePages displaying short descriptions of redirect targets or *Diffuse*-type galaxy

- [Ultra-diffuse galaxy](/source/Ultra-diffuse_galaxy) – Extremely low luminosity galaxyPages displaying short descriptions of redirect targets

- [Dark matter halo](/source/Dark_matter_halo) – Theoretical cosmological structure

- [DGSAT I](/source/DGSAT_I) – Ultra diffuse galaxy in the Perseus–Pisces Supercluster

## References

1. ^ [***a***](#cite_ref-Dokkum_1-0) [***b***](#cite_ref-Dokkum_1-1) [***c***](#cite_ref-Dokkum_1-2) 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](/source/ArXiv_(identifier)):[1410.8141](https://arxiv.org/abs/1410.8141). [Bibcode](/source/Bibcode_(identifier)):[2015ApJ...798L..45V](https://ui.adsabs.harvard.edu/abs/2015ApJ...798L..45V). [doi](/source/Doi_(identifier)):[10.1088/2041-8205/798/2/L45](https://doi.org/10.1088%2F2041-8205%2F798%2F2%2FL45). [S2CID](/source/S2CID_(identifier)) [119279968](https://api.semanticscholar.org/CorpusID:119279968).

1. ^ [***a***](#cite_ref-Dokkum1May2015_2-0) [***b***](#cite_ref-Dokkum1May2015_2-1) [***c***](#cite_ref-Dokkum1May2015_2-2) 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](/source/Astrophysical_Journal)*. **804** (1): L26. [arXiv](/source/ArXiv_(identifier)):[1504.03320](https://arxiv.org/abs/1504.03320). [Bibcode](/source/Bibcode_(identifier)):[2015ApJ...804L..26V](https://ui.adsabs.harvard.edu/abs/2015ApJ...804L..26V). [doi](/source/Doi_(identifier)):[10.1088/2041-8205/804/1/L26](https://doi.org/10.1088%2F2041-8205%2F804%2F1%2FL26). [S2CID](/source/S2CID_(identifier)) [54664026](https://api.semanticscholar.org/CorpusID:54664026).

1. **[^](#cite_ref-Phys.org-2015-05-14_3-0)** ["Scientists discover the fluffiest galaxies"](http://phys.org/news/2015-05-scientists-fluffiest-galaxies.html). [phys.org](/source/Phys.org). 14 May 2015.

1. **[^](#cite_ref-DF_1_4-0)** ["Dragonfly 44: Ultra-Diffuse Galaxy Made Mostly of Dark Matter"](http://www.sci-news.com/astronomy/dragonfly-44-ultra-diffuse-galaxy-dark-matter-04135.html). Sci.News. 25 August 2016. Retrieved 21 January 2024.

1. **[^](#cite_ref-5)** Van Dokkum, Pieter; Wasserman, Asher; Danieli, Shany; Abraham, Roberto; Brodie, Jean; Conroy, Charlie; Forbes, Duncan A.; Martin, Christopher; Matuszewski, Matt; Romanowsky, Aaron J.; Villaume, Alexa (2019). ["Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits, Peter van Dokkum et al. 2019"](https://doi.org/10.3847%2F1538-4357%2Fab2914). *The Astrophysical Journal*. **880** (2): 91. [arXiv](/source/ArXiv_(identifier)):[1904.04838](https://arxiv.org/abs/1904.04838). [doi](/source/Doi_(identifier)):[10.3847/1538-4357/ab2914](https://doi.org/10.3847%2F1538-4357%2Fab2914). [S2CID](/source/S2CID_(identifier)) [119185644](https://api.semanticscholar.org/CorpusID:119185644).

1. **[^](#cite_ref-6)** Saifollahi, Teymoor; Trujillo, Ignacio; Beasley, Michael A.; Peletier, Reynier F.; Knapen, Johan H. (2020). [""The number of globular clusters around the iconic UDG DF44 is as expected for dwarf galaxies", Saifollahi et al. 2020"](https://doi.org/10.1093%2Fmnras%2Fstaa3016). *Monthly Notices of the Royal Astronomical Society*. **502** (4): 5921–5934. [arXiv](/source/ArXiv_(identifier)):[2006.14630](https://arxiv.org/abs/2006.14630). [doi](/source/Doi_(identifier)):[10.1093/mnras/staa3016](https://doi.org/10.1093%2Fmnras%2Fstaa3016). [S2CID](/source/S2CID_(identifier)) [220127887](https://api.semanticscholar.org/CorpusID:220127887).

1. **[^](#cite_ref-PZ_1_7-0)** ["The puzzle of the strange galaxy made of 99.99% dark matter is solved"](https://www.iac.es/en/outreach/news/puzzle-strange-galaxy-made-9999-dark-matter-solved). [Instituto de Astrofísica de Canarias](/source/Instituto_de_Astrof%C3%ADsica_de_Canarias). 13 October 2020. Retrieved 21 January 2024.

1. **[^](#cite_ref-8)** Bogdan, Akos (2020). [""The American Astronomical Society, find out more The Institute of Physics, find out more The Archetypal Ultra-diffuse Galaxy, Dragonfly 44, Is not a Dark Milky Way", Bogdan 2020"](https://doi.org/10.3847%2F2041-8213%2Fabb886). *The Astrophysical Journal Letters*. [arXiv](/source/ArXiv_(identifier)):[2009.07846](https://arxiv.org/abs/2009.07846). [doi](/source/Doi_(identifier)):[10.3847/2041-8213/abb886](https://doi.org/10.3847%2F2041-8213%2Fabb886). [S2CID](/source/S2CID_(identifier)) [221761669](https://api.semanticscholar.org/CorpusID:221761669).

1. **[^](#cite_ref-9)** Crosswell, Ken (26 July 2016). ["The Milky Way's dark twin revealed"](http://www.nature.com/news/the-milky-way-s-dark-twin-revealed-1.20333). [Nature](/source/Nature_(journal)) News. Retrieved 30 July 2016.

1. **[^](#cite_ref-WashPost-2016-08-25_10-0)** Rachel Feltman (25 August 2016). ["A new class of galaxy has been discovered, one made almost entirely of dark matter"](https://www.washingtonpost.com/news/speaking-of-science/wp/2016/08/25/a-new-class-of-galaxy-has-been-discovered-one-made-almost-entirely-of-dark-matter/). *[The Washington Post](/source/The_Washington_Post)*.

1. **[^](#cite_ref-GM_1_11-0)** Byrd, D. (30 August 2016). ["A galaxy made of 99.9% dark matter"](https://earthsky.org/space/dragonfly-44-dark-matter-galaxy-2016). EarthSky Communications. Retrieved 21 January 2024.

1. **[^](#cite_ref-AJL-20160825_12-0)** Van Dokkum, Pieter; et al. (25 August 2016). ["A High Stellar Velocity Dispersion and ~100 Globular Clusters For The Ultra-Diffuse Galaxy Dragonfly 44"](http://scholarworks.sjsu.edu/physics_astron_pub/174). *[The Astrophysical Journal Letters](/source/The_Astrophysical_Journal_Letters)*. **828** (1): L6. [arXiv](/source/ArXiv_(identifier)):[1606.06291](https://arxiv.org/abs/1606.06291). [Bibcode](/source/Bibcode_(identifier)):[2016ApJ...828L...6V](https://ui.adsabs.harvard.edu/abs/2016ApJ...828L...6V). [doi](/source/Doi_(identifier)):[10.3847/2041-8205/828/1/L6](https://doi.org/10.3847%2F2041-8205%2F828%2F1%2FL6). [S2CID](/source/S2CID_(identifier)) [1275440](https://api.semanticscholar.org/CorpusID:1275440).

1. **[^](#cite_ref-NS-20160825_13-0)** Hall, Shannon (25 August 2016). ["Ghost galaxy is 99.99 per cent dark matter with almost no stars"](https://www.newscientist.com/article/2102584-ghost-galaxy-is-99-99-per-cent-dark-matter-with-almost-no-stars/). *[New Scientist](/source/New_Scientist)*. Retrieved 27 August 2016.

1. **[^](#cite_ref-WP-20160826_14-0)** Feltman, Rachael (26 August 2016). ["A new class of galaxy has been discovered, one made almost entirely of dark matter"](https://www.washingtonpost.com/news/speaking-of-science/wp/2016/08/25/a-new-class-of-galaxy-has-been-discovered-one-made-almost-entirely-of-dark-matter). *[The Washington Post](/source/The_Washington_Post)*. Retrieved 26 August 2016.

## External links

- Media related to [Dragonfly 44](https://commons.wikimedia.org/wiki/Category:Dragonfly_44) at Wikimedia Commons

v t e Constellation of Coma Berenices List of stars in Coma Berenices Coma Berenices in Chinese astronomy Stars Bayer α (Diadem) β γ Flamsteed 7 11 12 13 14 16 17 21 23 (Phyllon Kissinou) 24 31 35 36 37 41 Variable FK GP IN LW HR 4668 HD 107146 108863 108874 110067 114762 b 115404 116029 Other 2MASS J12195156+3128497 KELT-6 WASP-56 WISE 1217+1626 Exoplanets HD 108874 b c KELT-6b Star clusters Coma Star Cluster Messier 53 NGC 4147 NGC 5053 Nebulae LoTr 5 Galaxies Messier 64 (Black Eye Galaxy) 85 88 91 98 99 100 NGC 4014 4015 4017 4053 4056 4060 4061 4065 4066 4070 4072 4074 4076 4084 4086 4089 4090 4091 4092 4093 4095 4098 4136 4146 4150 4162 4185 4189 4203 4211 4212 4213 4222 4237 4245 4253 4262 4274 4278 4293 4298 4302 4308 4310 4312 4314 4323 4328 4340 4359 4375 4383 4393 4394 4414 4419 4448 4450 4455 4459 4468 4473 4474 4475 4477 4479 4489 4494 4495 4498 4502 4506 4515 4516 4523 4525 4540 4555 4556 4558 4559 4561 4565 4571 4585 4595 4611 4614 4615 4633 4634 4651 4659 4670 4673 4676 (Mice Galaxies) 4689 4692 4710 4712 4725 4747 4839 4848 4860 4869 4871 4872 4873 4874 4875 4876 4881 4883 4886 4889 4892 4895 4907 4911 4919 4921 4944 5000 5004 5012 5032 5056 5172 Other 3C 275.1 3C 287 Arp 60 Coma Berenices Dragonfly 44 IC 755 (NGC 4019) IC 831 IC 860 IC 3505 IC 3528 IC 4040 IC 4051 IOK-1 IRAS F12032+1707 LEDA 83677 M85-HCC1 Malin 1 PGC 44691 PKS 1155+251 PKS 1222+216 VIRGOHI21 ZwCl 1305.4+2941 BCG Galaxy clusters Abell 1413 Coma I Coma Cluster Coma Supercluster M94 Group NGC 4065 Group NGC 4631 Group Astronomical events GRB 050509B iPTF14atg SN 1940B SN 1979C SN 2005ap SN 2006X SN 2020oi Category

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