# Messier 80

Messier 80
A Hubble Space Telescope (HST) image of M80
Observation data (J2000 epoch)
ClassII[1]
ConstellationScorpius
Right ascension16h 17m 02.41s[2]
Declination–22° 58′ 33.9″[2]
Distance32.6 kly (10.0 kpc)[3]
Apparent magnitude (V)+7.87[4]
Apparent dimensions (V)10′.0
Physical characteristics
Mass5.02×105[5] M
Metallicity${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = –1.47[6] dex
Estimated age12.54 Gyr[6]
Other designationsM80, NGC 6093, GCl 39[4]

Messier 80 (also known as M80 or NGC 6093) is a globular cluster in the constellation Scorpius. It was discovered by Charles Messier in 1781.

This star cluster is, as to its angle from the solar system, midway between α Scorpii (Antares) and β Scorpii in a field in the Milky Way Galaxy that is rich in nebulæ. With low levels of light pollution it can be viewed below the 67th parallel north with modest amateur telescopes, appearing as a mottled ball of light.

It has an apparent angular diameter of about 10 arcminutes. Since it is 32,600 light-years (10,000 pc) away, this translates into a true (spatial) diameter of about 95 light-years. It contains several hundred thousand stars, and ranks among the densest globular clusters in the Milky Way. It is at more than twice the distance of the Galactic Center in regions considered the Galactic halo.

It hosts relatively many blue stragglers, stars that appear to be much younger than the cluster. It is thought these have lost part of their outer layers due to close encounters with other cluster members or perhaps from collisions between stars in the dense cluster. Images from the Hubble Space Telescope have shown pronounced districts of these stragglers in M80, suggesting the center of the cluster to have a very high capture and collision rate.

On May 21, 1860, a nova was found in M80 that delivered a magnitude of +7.0 to telescopes, binoculars and astute eyes. This variable star, given designation T Scorpii, reached an absolute magnitude of −8.5, briefly outshining the cluster.

## References

1. ^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
2. ^ a b 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, S2CID 119183070.
3. ^ Paust, Nathaniel E. Q.; et al. (February 2010), "The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions", The Astronomical Journal, 139 (2): 476–491, Bibcode:2010AJ....139..476P, doi:10.1088/0004-6256/139/2/476, hdl:2152/34371.
4. ^ a b "M 80". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 16, 2006.
5. ^ 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, S2CID 118649860.
6. ^ a b Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters", Monthly Notices of the Royal Astronomical Society, 404 (3): 1203–1214, arXiv:1001.4289, Bibcode:2010MNRAS.404.1203F, doi:10.1111/j.1365-2966.2010.16373.x, S2CID 51825384.