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 | |
|---|---|
 | |
| Observation data (J2000 epoch) | |
| Right ascension | 18h 38m 31.2s[1] |
| Declination | +05° 29′ 24″[1] |
| Distance | 1.3 kly (400 pc) |
| Apparent magnitude (V) | 4.6[1] |
| Physical characteristics | |
| Other designations | Cr 386, Mel 210 |
| Associations | |
| Constellation | Serpens |
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]
Stars
editThere 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
edit- ^ a b c "IC 4756". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 November 2016.
- ^ Michael Bakich. "The Omega Nebula, Graff's Cluster, and planetary nebula IC 1295". astronomy.com. Retrieved 2020-10-05.
- ^ O'Meara, Stephen James (2007). Deep-Sky Companions: Hidden Treasures. Cambridge University Press. p. 457-458. ISBN 978-0521-83704-0.
- ^ 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, arXiv:1804.01975, Bibcode:2018A&A...615A.165B, doi:10.1051/0004-6361/201832695, S2CID 118857628
- ^ "HR 7008 – Star in Cluster". SIMBAD. Retrieved 14 December 2014.
- ^ 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. Bibcode:1999AN....320...35A. doi:10.1002/1521-3994(199903)320:1<35::aid-asna35>3.0.co;2-f.
- ^ Ibanoǧlu, C.; Evren, S.; Taş, G.; Çakırlı, Ö.; Bozkurt, Z.; Afşar, M.; Sipahi, E.; Dal, H. A.; Özdarcan, O.; Çamurdan, D. Z.; Çamurdan, M.; Frasca, A. (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. Bibcode:2009MNRAS.392..757I. doi:10.1111/j.1365-2966.2008.14087.x.
- ^ Costa, J. E. S.; Michel, E.; Peña, J.; Creevey, O.; Li, Z. P.; Chevreton, M.; Belmonte, J. A.; Alvarez, M.; Fox Machado, L.; Parrao, L.; Pérez Hernéndez, F.; Fernández, A.; Fremy, J. R.; Pau, S.; Alonso, R. (2007). "Pulsational frequencies of the eclipsing δ Scuti star HD 172189. Results of the STEPHI XIII campaign". Astronomy and Astrophysics. 468 (2): 637–642. arXiv:0706.4083. Bibcode:2007A&A...468..637C. doi:10.1051/0004-6361:20065784.
External links
edit
Media related to IC 4756 at Wikimedia Commons- IC 4756 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
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