NGC 2173
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| NGC 2173 | |
|---|---|
 | |
| Observation data (J2000 epoch) | |
| Constellation | Mensa[1] |
| Right ascension | 05h 57m 58.0s[2] |
| Declination | −72° 58′ 42″[2] |
| Distance | 158.8 ± 3.3 kly (48.7 ± 1.0 kpc)[3] |
| Apparent magnitude (V) | 11.88[4] |
| Apparent dimensions (V) | 2.60″[2] |
| Physical characteristics | |
| Mass | ~105[5] M☉ |
| Metallicity | [Fe/H] = −0.42[4] dex |
| Estimated age | 1.7±0.2 Gyr.[5] |
| Other designations | NGC 2173, SL 807, LW 348, ESO 33SC34[2][6] |
NGC 2173 is a globular cluster of stars in the southern constellation of Mensa.[1] It was discovered on February 8, 1836 by English astronomer John Herschel.[7] The cluster has an apparent visual magnitude of 11.88,[4] and an angular size of 2.60″.[2] It is located at a distance of approximately 159,000 ly (48.7 kpc) from the Sun.[3]
The cluster is located within the Large Magellanic Cloud, to the southeast of the galaxy's center at a separation of around 11,000 ly (3.5 kpc). A 1986 age estimate based on the main sequence turnoff found a value of 1.8±0.7 Gyr.[8] This was later refined to 1.7±0.2 Gyr.[5] Variations in lower mass element abundances suggest that the cluster has at least two distinct stellar populations with different ages.[5]
In 2018, it was announced by Li et al (2018) that the blue straggler stars in the cluster formed two distinct sequences.[9] However, an objection was raised that this finding was an artifact of field contamination: by applying decontamination techniques, one of the sequences could be shown to be unrelated to the cluster.[10] With the availability of higher precision proper motion data, the existence of the bifurcatated sequence was apparently reconfirmed by Wang et al (2025).[11]