|Observation data (J2000 epoch)|
|Right ascension||19h 53m 46.49s|
|Declination||+18° 46′ 45.1″|
|Distance||13.0 kly (4.0 kpc)|
|Apparent magnitude (V)||+6.1|
|Apparent dimensions (V)||7′.2|
|Metallicity||= –0.78 dex|
|Estimated age||9-10 Gyr|
|Other designations||M71, NGC 6838, Cr 409, GCl 115|
Messier 71 (also known as M71 or NGC 6838) is a globular cluster in the small northern constellation Sagitta. It was discovered by Philippe Loys de Chéseaux in 1745 and included by Charles Messier in his catalog of non-comet-like objects in 1780. It was also noted by Koehler at Dresden around 1775.
M71 was for many decades thought (until the 1970s) to be a densely packed open cluster and was classified as such by leading astronomers in the field of star cluster research due to its lacking a dense central compression, and to its stars having more "metals" than is usual for an ancient globular cluster; furthermore, it lacks the RR Lyrae "cluster" variable stars that are common in most globulars. However, modern photometric photometry has detected a short "horizontal branch" in the H-R diagram (chart of temperature versus luminosity) which is characteristic of a globular cluster. The shortness of the branch explains the lack of RR Lyrae variables and is due to the globular's relatively young age of 9–10 billion years. Taking in many or only late series (Population I) stars explains relatively its stars. Hence today M71 is designated as a very loosely concentrated globular cluster, much like M68 in Hydra. M71 has a mass of about 53,000 M☉ and a luminosity of around 19,000 L☉.
|Wikimedia Commons has media related to Messier 71.|
- Goldsbury, Ryan; et al. (December 2010), "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters", The Astronomical Journal, 140 (6): 1830–1837, arXiv:1008.2755, Bibcode:2010AJ....140.1830G, doi:10.1088/0004-6256/140/6/1830.
- Hessels, J. W. T.; et al. (November 2007), "A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters", The Astrophysical Journal, 670 (1): 363–378, arXiv:0707.1602, Bibcode:2007ApJ...670..363H, doi:10.1086/521780.
- "M 71". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-17.
- Marks, Michael; Kroupa, Pavel (August 2010), "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way", Monthly Notices of the Royal Astronomical Society, 406 (3): 2000–2012, arXiv:1004.2255, Bibcode:2010MNRAS.406.2000M, doi:10.1111/j.1365-2966.2010.16813.x. Mass is from MPD on Table 1.
- distance × sin( diameter_angle / 2 ) = 13 ly. radius
- Boyles, J.; et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal, 742 (1): 51, arXiv:1108.4402, Bibcode:2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51.
- "New General Catalog Objects: NGC 6800 - 6849". cseligman.com. Retrieved 2021-03-11.
- "Z Sge". The International Variable Star Index. AAVSO. Retrieved 1 March 2021.
- Dalgleish, H.; Kamann, S.; Usher, C.; Baumgardt, H.; Bastian, N.; Veitch-Michaelis, J.; Bellini, A.; Martocchia, S.; Da Costa, G. S.; Mackey, D.; Bellstedt, S.; Pastorello, N.; Cerulo, P. (March 2020). "The WAGGS project-III. Discrepant mass-to-light ratios of Galactic globular clusters at high metallicity". Monthly Notices of the Royal Astronomical Society. 492 (3): 3859–3871. doi:10.1093/mnras/staa091. Retrieved 1 March 2021.
- Messier 71 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- Messier71 @ SEDS Messier pages
- Messier 71, Galactic Globular Clusters Database page
- Messier 71, LRGB CCD image based on two hours total exposure
- Messier 71: an Unusual Globular Cluster, ESA\Hubble picture of the week.
- McCormac, James; Szymanek, Nik. "M71 – Globular Cluster". Deep Sky Videos. Brady Haran.