NGC_637 Latitude and Longitude:
Sky map 01h 43.1m 0s, +64° 02′ 0″
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NGC 637
NGC 637 DSS
Observation data (J2000.0 epoch)
Right ascension01h 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 designations Cr 17, NGC 637 [4]
Associations
Constellation Cassiopeia
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. ^ a b c d 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. arXiv: 0909.3737. Bibcode: 2009MNRAS.399.2146W. doi: 10.1111/j.1365-2966.2009.15416.x. S2CID  6066790.
  2. ^ a b c d O'Meara, Steve (June 14, 2007). Herschel 400 Observing Guide. Cambridge University Press. p. 296. ISBN  9780521858939.
  3. ^ a b c 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. arXiv: 0810.1409. Bibcode: 2008MNRAS.390..985Y. doi: 10.1111/j.1365-2966.2008.13740.x. S2CID  18096918.
  4. ^ "NGC 637". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-29.
  5. ^ Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. Vol. 1. Sky Publishing Corporation and the European Space Agency. p. 34. ISBN  0-933346-84-0.
  6. ^ "New General Catalog Objects: NGC 600 - 649". cseligman.com. Retrieved 2018-01-05.
  7. ^ a b c d Kharchenko, N. V.; et al. (August 2005). "Astrophysical parameters of Galactic open clusters". Astronomy and Astrophysics. 438 (3): 1163–1173. arXiv: astro-ph/0501674. Bibcode: 2005A&A...438.1163K. doi: 10.1051/0004-6361:20042523. S2CID  9079873.
  8. ^ a b 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. arXiv: 0808.1785. Bibcode: 2008Ap&SS.318...25H. doi: 10.1007/s10509-008-9888-2. S2CID  18982625.
  9. ^ Handler, G.; Meingast, S. (September 2011). "New β Cephei stars in the young open cluster NGC 637". Astronomy & Astrophysics. 533: 6. arXiv: 1105.3121. Bibcode: 2011A&A...533A..70H. doi: 10.1051/0004-6361/201116874. S2CID  55061600. A70.

External links

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