NGC 7209

NGC 7209
NGC 7209 in optical light
Observation data (J2000 epoch)
Right ascension22h 05m 07s[1]
Declination+46° 29′ 00″[1]
Distance3,810 ly (1,168 pc[2])
Apparent magnitude (V)7.7 [1]
Apparent dimensions (V)25'
Physical characteristics
Mass278[3] M☉
Estimated age420 million years[2]
Other designationsCr 444
Associations
ConstellationLacerta
See also: Open cluster, List of open clusters

NGC 7209 is an open cluster in the constellation Lacerta. It was discovered by William Herschel on 19 October 1787. The cluster lies 3,810 light years away from Earth. It has been suggested that there is another cluster at a distance of 2,100 light years projected in front of a cluster lying at 3,800 light years away, based on the reddening of the cluster,[4] however, further photometric studies of the cluster did not support that claim.[5]

The cluster is made up out of 150 stars with magnitude from 9 to 15[6] within a tidal radius of 9 parsec (30 light years).[3] From its members, 3 are probably delta Scuti variables.[7] One other member of the cluster is the variable SS Lancertae, a binary star with 14.4 day period whose magnitude stopped varying in the middle of the 20th century. This has been attributed to the presence of a third star with period 679 days, whose perturbations change the line of sight. The nodal cycle is found to be about 600 years, within which occur two ecliptic phases, each lasting about 100 yr.[8]

  1. ^ a b c "NGC 7209". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-23.
  2. ^ a b WEBDA: NGC 7209
  3. ^ a b Piskunov, A. E.; Schilbach, E.; Kharchenko, N. V.; Röser, S.; Scholz, R.-D. (6 November 2007). "Tidal radii and masses of open clusters". Astronomy & Astrophysics. 477 (1): 165–172. Bibcode:2008A&A...477..165P. doi:10.1051/0004-6361:20078525.
  4. ^ Peña, J. H.; Peniche, R. (1 October 1994). "uvby-beta photometry of open clusters. IV. NGC 1444, NGC 1662, NGC 2129, NGC 2169, and NGC 7209". Revista Mexicana de Astronomía y Astrofísica. 28: 139–152. Bibcode:1994RMxAA..28..139P. ISSN 0185-1101.
  5. ^ Vansevicius, V.; Platais, I.; Paupers, O.; Abolins, E. (11 March 1997). "A study of the open cluster NGC 7209 in the Vilnius photometric system". Monthly Notices of the Royal Astronomical Society. 285 (4): 871–878. Bibcode:1997MNRAS.285..871V. doi:10.1093/mnras/285.4.871.
  6. ^ O'Meara, Stephen James (2011). Deep-Sky Companions: The Secret Deep. Cambridge University Press. pp. 445–447. ISBN 9781139500074.
  7. ^ Van Cauteren, P. (2005). "Search for intrinsic variable stars in three open clusters: NGC 1664, NGC 6811 and NGC 7209". Communications in Asteroseismology (in German). 146: 21–32. Bibcode:2005CoAst.146...21V. doi:10.1553/cia146s21. ISSN 1021-2043.
  8. ^ Torres, Guillermo (April 2001). "The Change in the Inclination Angle of the Noneclipsing Binary SS Lacertae: Future Eclipses". The Astronomical Journal. 121 (4): 2227–2238. arXiv:astro-ph/0012542. Bibcode:2001AJ....121.2227T. doi:10.1086/319942. S2CID 15616832.