Messier 19

Messier 19 or M19 (also designated NGC 6273) is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier on June 5, 1764<ref name=thompson2007/> and added to his catalogue of comet-like objects that same year. It was resolved into individual stars by William Herschel in 1784. His son, John Herschel, described it as "a superb cluster resolvable into countless stars".<ref name=burnham1978/> The cluster is located 4.5° WSW of Theta Ophiuchi and is just visible as a fuzzy point of light using Template:Convert binoculars. Using a telescope with a Template:Convert aperture, the cluster shows an oval appearance with a Template:Nowrap core and a Template:Nowrap halo.<ref name=thompson2007/>

M19 is one of the most oblate of the known globular clusters.<ref name=burnham1978/> This flattening may not accurately reflect the physical shape of the cluster because the emitted light is being strongly absorbed along the eastern edge. This is the result of extinction caused by intervening gas and dust. When viewed in the infrared, the cluster shows almost no flattening.<ref name=aj135_5_1731/> It lies at a distance of about Template:Convert from the Solar System,<ref name=apj742_1_51/> and is quite near to the Galactic Center at only about Template:Convert away.<ref name=aaa450_1_105/>

This cluster contains an estimated 1,100,000 times the mass of the Sun<ref name=apj742_1_51/> and it is around 11.9 billion years old.<ref name=mnras404_3_1203/> The stellar population includes four Cepheids and RV Tauri variables, plus at least one RR Lyrae variable for which a period is known.<ref name=aj122_5_2587/> Observations made during the ROSAT mission failed to reveal any low-intensity X-ray sources.<ref name=aaa368_137/>

File:M19map.png

Map showing the location of M19

See also

• List of Messier objects

External links

• Messier 19, SEDS Messier pages
• Messier 19, Galactic Globular Clusters Database page
• Template:WikiSky