Aquarius II

Aquarius ll
Aquarius ll
Observation data
Constellation	Aquarius
Distance	180,000 ly[ contradictory ]
Characteristics
Size	160 pc
Notable features	Difficult detection
Other designations
	Aquarius 2, AQU 2, Aqu ll

Last updated August 21, 2025

Aquarius ll (also Aquarius 2, AQU 2 or Aqu ll) is a mildly elliptical dwarf satellite galaxy to the Milky Way located around 110 kiloparsecs ^{[ contradictory ]} from Earth in the constellation of Aquarius. It has a size of 160 parsecs. Aquarius ll is currently moving away from the galactic center of the Milky Way. This galaxy contains many old red giant branch stars that are predominantly metal poor.^[1]^[2]^[3]

It is located just 9 kiloparsecs from the Large Magellanic Cloud (LMC). Whether this is an association or coincidence is uncertain. Other dwarf galaxies discovered likely do have some association with the Magellanic Clouds.^[1]

Discovery

It was discovered using the Very Large Telescope (VLT) and the Sloan Digital Sky Survey (SDSS). When it was found, it was initially identified as an over density of red giant branch stars. Detection of Aquarius ll was difficult as it lies close to the detection boundary of both luminosity and surface brightness,which is why it was not identified earlier and making it one of the most difficult dwarf galaxies to discover.^[1]

Reference

1 2 3 Torrealba, G.; Koposov, S. E.; Belokurov, V.; Irwin, M.; Collins, M.; Spencer, M.; Ibata, R.; Mateo, M.; Bonaca, A.; Jethwa, P. (2016-11-21). "At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data". Monthly Notices of the Royal Astronomical Society. 463 (1): 712–722. arXiv: 1605.05338 . doi: 10.1093/mnras/stw2051 . ISSN 0035-8711.
↑ "Aquarius II". New Planetarium. Retrieved 2025-07-13.
↑ Bruce, Jordan; Li, Ting S.; Pace, Andrew B.; Heiger, Mairead; Song, Ying-Yi; Simon, Joshua D. (2023-06-01). "Spectroscopic Analysis of Milky Way Outer Halo Satellites: Aquarius II and Boötes II". The Astrophysical Journal. 950 (2): 167. arXiv: 2302.03708 . Bibcode:2023ApJ...950..167B. doi: 10.3847/1538-4357/acc943 . ISSN 0004-637X.

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[:0-1] 1 2 3 Torrealba, G.; Koposov, S. E.; Belokurov, V.; Irwin, M.; Collins, M.; Spencer, M.; Ibata, R.; Mateo, M.; Bonaca, A.; Jethwa, P. (2016-11-21). "At the survey limits: discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data". Monthly Notices of the Royal Astronomical Society. 463 (1): 712–722. arXiv: 1605.05338 . doi: 10.1093/mnras/stw2051 . ISSN 0035-8711.

[2] "Aquarius II". New Planetarium. Retrieved 2025-07-13.

[3] Bruce, Jordan; Li, Ting S.; Pace, Andrew B.; Heiger, Mairead; Song, Ying-Yi; Simon, Joshua D. (2023-06-01). "Spectroscopic Analysis of Milky Way Outer Halo Satellites: Aquarius II and Boötes II". The Astrophysical Journal. 950 (2): 167. arXiv: 2302.03708 . Bibcode:2023ApJ...950..167B. doi: 10.3847/1538-4357/acc943 . ISSN 0004-637X.

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