Astronomy:NGC 637

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Short description: Open star cluster in the constellation Cassiopeia
NGC 637
NGC 637 DSS
Observation data (J2000.0 epoch)
ConstellationCassiopeia
Right ascension 01h 43m 04.0s[1]
Declination+64° 02′ 24″[1]
Distance7.045 ± 1.409 kly (2.160 ± 0.432 kpc)[1]
Apparent magnitude (V)8.2[2]
Apparent dimensions (V)4.2′[3]
Physical characteristics
Estimated age10 ± 5 Myr[3]
Other designationsCr 17, NGC 637[4]
See also: Open cluster, List of open clusters

NGC 637 is an open cluster of stars in the northern constellation of Cassiopeia, positioned about 1.5° to the WNW of the star Epsilon Cassiopeiae.[2][5] The cluster was discovered on 9 November 1787 by German-born English astronomer William Herschel.[6] It is located in the Perseus Arm of the Milky Way,[7] at a distance of approximately 7.045 kilolight-years from the Sun.[1] The cluster is small but compact, and is readily visible in a small telescope.[2]

This is a young cluster with an estimated age of 5–15 million years.[3] It has a Trumpler class of I2m, indicating it is strongly concentrated (I) with an intermediate range of brightness variation (2) and a moderate richness of stars (m).[7] The cluster has 55[2] members and an angular radius of 4′.2, corresponding to a physical radius of 9.8 ly (3.0 pc).[7] It has a core radius of 0.36′±0.13′.[8]

The seven brightest members are all over 10th magnitude, with five known to be variable. A total of four β Cephei-type variables have been identified, one of the highest such totals for an open cluster.[9] A classical Be star candidate has been detected.[7] The distribution of the cluster's stars on the Hertzsprung–Russell diagram shows a noticeable gap on the main sequence, which is not explained by missing data.[8]

References

  1. ↑ 1.0 1.1 1.2 1.3 Wu, Zhen-Yu et al. (November 2009). "The orbits of open clusters in the Galaxy". Monthly Notices of the Royal Astronomical Society 399 (4): 2146–2164. doi:10.1111/j.1365-2966.2009.15416.x. Bibcode: 2009MNRAS.399.2146W. 
  2. ↑ 2.0 2.1 2.2 2.3 O'Meara, Steve (June 14, 2007). Herschel 400 Observing Guide. Cambridge University Press. p. 296. ISBN 9780521858939. https://books.google.com/books?id=Nyh9fAC_tpIC&pg=PA296. 
  3. ↑ 3.0 3.1 3.2 Yadav, R. K. S.; Kumar, Brijesh; Subramaniam, A.; Sagar, Ram et al. (November 2008). "Optical and near-infrared photometric study of the open cluster NGC 637 and 957". Monthly Notices of the Royal Astronomical Society 390 (3): 985–996. doi:10.1111/j.1365-2966.2008.13740.x. Bibcode: 2008MNRAS.390..985Y. 
  4. ↑ "NGC 637". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+637. 
  5. ↑ Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. 1. Sky Publishing Corporation and the European Space Agency. p. 34. ISBN 0-933346-84-0. 
  6. ↑ "New General Catalog Objects: NGC 600 - 649" (in en-US). http://cseligman.com/text/atlas/ngc6.htm#637. 
  7. ↑ 7.0 7.1 7.2 7.3 Kharchenko, N. V. et al. (August 2005). "Astrophysical parameters of Galactic open clusters". Astronomy and Astrophysics 438 (3): 1163–1173. doi:10.1051/0004-6361:20042523. Bibcode: 2005A&A...438.1163K. 
  8. ↑ 8.0 8.1 Hasan, Priya et al. (November 2008). "The structure and dynamics of young star clusters: King 16, NGC 1931, NGC 637 and NGC 189". Astrophysics and Space Science 318 (1–2): 25–33. doi:10.1007/s10509-008-9888-2. Bibcode: 2008Ap&SS.318...25H. 
  9. ↑ Handler, G.; Meingast, S. (September 2011). "New β Cephei stars in the young open cluster NGC 637". Astronomy & Astrophysics 533: 6. doi:10.1051/0004-6361/201116874. A70. Bibcode: 2011A&A...533A..70H. 

External links

Coordinates: Sky map 01h 43.1m 0s, +64° 02′ 0″



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