Astronomy:IC 4756

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Short description: Open cluster in the constellation Serpens
IC 4756
IC 4756.png
Observation data (J2000 epoch)
ConstellationSerpens
Right ascension 18h 38m 31.2s[1]
Declination+05° 29′ 24″[1]
Distance1.3 kly (400 pc)
Apparent magnitude (V)4.6[1]
Physical characteristics
Other designationsCr 386, Mel 210
See also: Open cluster, List of open clusters

IC 4756 is a large bright open cluster in the constellation Serpens. Known as Graff's Cluster, it is bright enough to be seen with the naked eye and considered a fine cluster for binoculars or small telescopes.[2]

IC 4756 is also known as the Tweedledee Cluster (paired with NGC 6633 as Tweedledum), also as the Secret Garden Cluster.[3]

Metallicity of IC 4756 is similar to the Sun, at -0.02±0.01 dex.[4]

Open star clusters IC 4756 (left) and NGC 6633. Original astrophoto.

Stars

There are some noteworthy stars in the cluster. HD 172365[5] is a likely post-blue straggler in the IC 4756 that contains a large excess of lithium.[6] HD 172189, also in IC 4756, is an Algol variable eclipsing binary[7] with a 5.70 day period. The primary star in the system is also a Delta Scuti variable, undergoing multiple pulsation frequencies, which, combined with the eclipses, causes the system to vary by around a tenth of a magnitude.[8]

References

  1. ↑ 1.0 1.1 1.2 "IC 4756". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=IC+4756. 
  2. ↑ Michael Bakich. "The Omega Nebula, Graff's Cluster, and planetary nebula IC 1295". https://astronomy.com/observing/observing-podcasts/2014/07/the-omega-nebula-graffs-cluster-and-ic-1295. 
  3. ↑ O'Meara, Stephen James (2007). Deep-Sky Companions: Hidden Treasures. Cambridge University Press. p. 457-458. ISBN 978-0521-83704-0. 
  4. ↑ Bagdonas, Vilius; Drazdauskas, Arnas; Tautvaišienė, Gražina; Smiljanic, Rodolfo; Chorniy, Yuriy (2018), "Chemical composition of giant stars in the open cluster IC 4756", Astronomy & Astrophysics 615: A165, doi:10.1051/0004-6361/201832695, Bibcode: 2018A&A...615A.165B 
  5. ↑ "HR 7008 – Star in Cluster". SIMBAD. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+172365. 
  6. ↑ Andrievsky, S. M.; Gorlova, N. I.; Klochkova, V. G.; Kovtyuch, V. V.; Panchuk, V. E. (1999). "The Lithium-rich supergiant HD172365". Astronomische Nachrichten 320 (1): 35–41. doi:10.1002/1521-3994(199903)320:1<35::aid-asna35>3.0.co;2-f. Bibcode: 1999AN....320...35A. 
  7. ↑ Ibanoǧlu, C.; Evren, S.; Taş, G.; Çakırlı, Ö.; Bozkurt, Z.; Afşar, M.; Sipahi, E.; Dal, H. A. et al. (2009). "Spectroscopic and photometric observations of the selected Algol-type binaries - IV. V799 Cassiopeiae, BX Piscium and HD 172189". Monthly Notices of the Royal Astronomical Society 392 (2): 757. doi:10.1111/j.1365-2966.2008.14087.x. Bibcode: 2009MNRAS.392..757I. 
  8. ↑ Costa, J. E. S.; Michel, E.; Peña, J.; Creevey, O.; Li, Z. P.; Chevreton, M.; Belmonte, J. A.; Alvarez, M. et al. (2007). "Pulsational frequencies of the eclipsing δ Scuti star HD 172189. Results of the STEPHI XIII campaign". Astronomy and Astrophysics 468 (2): 637–642. doi:10.1051/0004-6361:20065784. Bibcode: 2007A&A...468..637C. 

External links


Coordinates: Sky map 18h 39m 04.9s, +05° 27′ 09″




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