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NGC 129

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NGC 129
DSS image of NGC 129
Observation data (J2000 epoch)
Right ascension00h 30m 00s[1]
Declination+60° 13′ 06″[1]
Distance5,450 ly (1,670 pc[2])
Apparent magnitude (V)6.5[3]
Apparent dimensions (V)12′[3]
Physical characteristics
Estimated age76 millions years[2]
Other designationsCollinder 2
Associations
ConstellationCassiopeia[3]
See also: Open cluster, List of open clusters

NGC 129 is an open cluster stars in the northern constellation of Cassiopeia.[3] It was discovered by William Herschel in 1788. It is located almost exactly halfway between the bright stars Caph (β Cassiopeiae) and γ Cassiopeiae. It is large but not dense and can be observed by binoculars, through which the most obvious component is a small triangle of stars of magnitude 8 and 9, located in the center of the cluster.

NGC 129 contains several giant stars. The brightest member of the cluster is DL Cassiopeiae, a binary system which contains a Cepheid variable with a 8,00 day period. Using the fluctuations of the brightness of DL Cassiopeia from 8,7 to 9,28, Gieren et al. in 1994 determined the distance of NGC 129 to be 2034 ±110 pc (6.630 ±360 ly), much larger than the distance obtained by Turner et al. (1992), who obtained a distance of 1,670 ±13 pc from ZAMS fitting of the cluster. A possible cause of this difference is the different level of obstruction of light and star reddening of the stars of the cluster.[4] One more cepheid variable, V379 Cas, is also a possible member of NGC 129.[5]

References

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  1. 1 2 "NGC 129". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2015-06-19.
  2. 1 2 Turner, David G.; Forbes, Douglas; Pedreros, Mario (September 1992). "Galactic clusters with associated Cepheid variables. II - NGC 129 and DL Cassiopeiae". Astronomical Journal. 104 (3): 1132–1143. Bibcode:1992AJ....104.1132T. doi:10.1086/116302.
  3. 1 2 3 4 Finlay, Warren H. (2014). Concise Catalogue of Deep-Sky Objects. The Patrick Moore Practical Astronomy Series (2nd ed.). Springer Cham. p. 145. doi:10.1007/978-3-319-03170-5. ISBN 978-3-319-03169-9.
  4. ↑ Gieren, W. P.; Welch, D. L.; Mermilliod, J.-C.; Matthews, J. M. & Hertling, G. (June 1994). "Independent distance determinations to Milky Way Cepheids in open clusters and associations. 1: The binary Cepheid DL CAS in NGC 129". The Astronomical Journal. 107 (6): 2093–2100. Bibcode:1994AJ....107.2093G. doi:10.1086/117019.
  5. ↑ Richard I. Anderson; Laurent Eyer & Nami Mowlavi (25 June 2013). "Cepheids in Open Clusters: An 8-D All-sky Census". Monthly Notices of the Royal Astronomical Society. 434 (3): 2238–2261. arXiv:1212.5119. Bibcode:2013MNRAS.434.2238A. doi:10.1093/mnras/stt1160.
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  • Wikimedia Commons logo Media related to NGC 129 at Wikimedia Commons
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