Messier 19 or M19 (also designated NGC 6273) is a globular cluster in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Ophiuchus. It was discovered by Charles Messier on June 5, 1764 and added to his catalogue of

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

-like objects that same year. It was resolved into individual stars by William Herschel in 1784. His son,

John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint and did botanical wor ...

, described it as "a superb cluster resolvable into countless stars". The cluster is located 4.5° WSW of

Theta Ophiuchi Theta Ophiuchi, Latinized from θ Ophiuchi, is a multiple star system in the equatorial constellation of Ophiuchus. It lies on the "right foot" of the serpent-bearer, just southwest of Kepler's Star, the nova of 1604. According to Richa ...

and is just visible as a fuzzy point of light using binoculars. Using a telescope with a

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

, the cluster shows an oval appearance with a core and a halo. M19 is one of the most

oblate In Christianity (especially in the Roman Catholic, Orthodox, Anglican and Methodist traditions), an oblate is a person who is specifically dedicated to God or to God's service. Oblates are individuals, either laypersons or clergy, normally livi ...

of the known globular clusters. 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 Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

caused by intervening gas and dust. When viewed in the infrared, the cluster shows almost no flattening. It lies at a distance of about from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

, and is quite near to the Galactic Center at only about away. This cluster contains an estimated 1,100,000 times the mass of the Sun and it is around 11.9 billion years old. The stellar population includes four

Cepheids A Cepheid variable () is a type of star that Instability strip, pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable frequency, period and amplitude. A strong direct period-l ...

and

RV Tauri variable RV Tauri variables are luminous variable stars that have distinctive light variations with alternating deep and shallow minima. History and discovery German astronomer Friedrich Wilhelm Argelander monitored the distinctive variations in brightne ...

s, plus at least one

RR Lyrae variable RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder. This class is named after the prototype and ...

for which a period is known. Observations made during the ROSAT mission failed to reveal any low-intensity X-ray sources. M19map

References

External links

Messier 19, SEDS Messier pages

Messier 19, Galactic Globular Clusters Database page
* {{Sky, 17, 02, 37.69, -, 26, 16, 04.6, 28000 Messier 019 Messier 019

019 Nineteen or 19 may refer to: * 19 (number), the natural number following 18 and preceding 20 * one of the years 19 BC, AD 19, 1919, 2019 Films * ''19'' (film), a 2001 Japanese film * ''Nineteen'' (film), a 1987 science fiction film Music ...

Messier 019 17640605

See also

References

External links