Messier 9 or M9 (also designated NGC 6333) 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 ...

of Ophiuchus. It is positioned in the southern part of the constellation to the southwest of

Eta Ophiuchi Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. Based on stellar parallax, parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the ...

, and lies atop a dark cloud of dust designated Barnard 64. The cluster was discovered by French astronomer Charles Messier on June 3, 1764, who described it as a "nebula without stars". In 1783, English astronomer William Herschel was able to use his reflector to resolve individual stars within the cluster. He estimated the cluster to be 7–8

′ The prime symbol , double prime symbol , triple prime symbol , and quadruple prime symbol are used to designate units and for other purposes in mathematics, science, linguistics and music. Although the characters differ little in appearance fr ...

in diameter with stars densely packed near the center. M9 has an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 7.9, an angular size of 9.3′, and can be viewed with a small

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

. It is one of the nearer globular clusters to the center of the galaxy as is around 5,500

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Galactic Center. Its distance from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

is 25,800 light-years. The total

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

of this cluster is around 120,000 times that of the Sun, the

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

being -8.04. The brightest individual

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s in M9 are of

13.5, making them visible in moderately sized

s. There have been 24

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

s found in M9: 21

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 ...

s, plus a

long-period variable The descriptive term long-period variable star refers to various groups of cool luminous pulsating variable stars. It is frequently abbreviated to LPV. Types of variation The General Catalogue of Variable Stars does not define a long-period vari ...

Type II Cepheid Type II Cepheids are variable stars which pulsate with periods typically between 1 and 50 days. They are population II stars: old, typically metal-poor, low mass objects. Like all Cepheid variables, Type IIs exhibit a relationship between the st ...

, and an

eclipsing binary A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

. No blue stragglers or

SX Phoenicis variable An SX Phoenicis variable is a type of variable star. These stars exhibit a short period pulsation behavior that varies on time scales of 0.03–0.08 days (0.7–1.9 hours). They have spectral classifications in the range A2-F5 and vary in magnitude ...

s have been discovered. Based upon the periods of the RR Lyr variables, this cluster is classified as an Oosterhoff type II globular, which precludes an extra-galactic origin. At about 80' ( degrees) to the northeast of M9 is the dimmer globular cluster

NGC 6356 NGC 6356 is a globular cluster located in the constellation Ophiuchus. It is designated as a II in the Shapley–Sawyer Concentration Class and was discovered by the German-born British astronomer William Herschel on 18 June 1784. The star cluster ...

, while about the same to the southeast is the globular

NGC 6342 NGC 6342 is a globular cluster located in the constellation Ophiuchus. Its Shapley–Sawyer Concentration Class is IV, and it was discovered by the German-born British astronomer William Herschel on 28 May 1786. It is at a distance of 28,000 light ...

Gallery

File:Messier object 009.jpg, Messier 9, from ''

2MASS The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and ...

'' File:M9map.png, Map showing the location of Messier 9

References

External links

Messier 9, SEDS Messier pages

M9, Galactic Globular Clusters Database page

The glittering stars of Messier 9
March 16, 2012, Tg Daily Staff, ''TG Daily'' * * {{Ngc65 Messier 009 Messier 009

009 009 may refer to: * OO9, gauge model railways * O09, FAA identifier for Round Valley Airport * 0O9, FAA identifier for Ward Field, see List of airports in California * British secret agent 009, see 00 Agent * BA 009, see British Airways Flight 9 * ...

Messier 009 17640528

Gallery

See also

References

External links