NGC 6208 is an open star cluster located in the southern constellation Ara. It was first recorded by James Dunlop on 6 May 1826 and later catalogued by John Herschel. The cluster is listed in several astronomical catalogs under additional designations, including Cr 313 and OCL 960.
Astronomical data
| Parameter | Value |
|---|---|
| Right ascension (J2000) | 16 h 54 m 00 s |
| Declination (J2000) | –62° 56′ 00″ |
| Constellation | Ara |
| Visual magnitude (V) | ~8.2 |
| Angular size | ~10 arcminutes |
| Distance from the Sun | ~1.2 kiloparsecs (≈ 4 × 10³ ly) |
| Estimated age | ~1 billion years |
| Estimated member count | ~90–120 stars (identified members) |
| Metallicity | Near solar ([Fe/H] ≈ 0.0) |
| Radial velocity | ~+20 km s⁻¹ (heliocentric) |
Physical characteristics
NGC 6208 is classified as an intermediate‑age open cluster. Its stellar population includes a mixture of main‑sequence stars, a few evolved giants, and a modest number of binary systems. Photometric studies indicate a relatively high degree of central concentration, typical for clusters of its age, and the color–magnitude diagram displays a well‑defined turn‑off point consistent with an age of about 1 Gyr.
Observational notes
- The cluster is best observed from southern latitudes during the months of May through August.
- With an integrated visual magnitude of ~8.2, it is not visible to the naked eye but can be imaged with modest amateur telescopes (≈ 8‑inch aperture) under dark skies.
- Photographic and CCD observations often employ Johnson‑Cousins B V filters to study its stellar population and derive age and distance estimates.
Scientific relevance
NGC 6208 serves as a valuable benchmark for studies of stellar evolution in intermediate‑age open clusters. Its relatively low reddening and well‑populated main sequence enable calibration of theoretical isochrones and investigations into dynamical processes such as mass segregation and cluster dissolution.
References
- SIMBAD Astronomical Database entry for NGC 6208.
- Dias, W. S., et al. (2002). “New catalogue of optically visible open clusters and candidates.” Astronomy & Astrophysics, 389, 871–873.
- Kharchenko, N. V., et al. (2013). “Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters.” Astronomy & Astrophysics, 558, A53.
All data reflect the consensus of peer‑reviewed astronomical literature as of 2026.
