Messier 13 or M13, also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster, is a

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

of several hundred thousand

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 the

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

Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the ...

Discovery and visibility

M13 was discovered by

Edmond Halley Edmond (or Edmund) Halley (; – ) was an English astronomer, mathematician and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory he constructed on Saint Helena in 1676–77, H ...

in 1714, and cataloged by

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose ...

on June 1, 1764, into his list of objects not to mistake for

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 ...

s; Messier's list, including Messier 13, eventually became known as the

Messier Catalog The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his ''Catalogue des Nébuleuses et des Amas d'Étoiles'' (''Catalogue of Nebulae and Star Clusters''). Because Messier was only int ...

. About one third of the way from Vega to Arcturus, four bright stars in Herculēs form the Keystone asterism, the broad torso of the hero. M13 can be seen in this asterism of the way north ( by west) from

Zeta Zeta (, ; uppercase Ζ, lowercase ζ; grc, ζῆτα, el, ζήτα, label= Demotic Greek, classical or ''zē̂ta''; ''zíta'') is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived f ...

to Eta Herculis. Although only telescopes with great light-gathering capability fully resolve the stars of the cluster, M13 may be visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to norma ...

depending on circumstances. With a low-power telescope, Messier 13 looks like a comet or fuzzy patch. The cluster is visible throughout the year from latitudes greater than 36 degrees north, with the longest visibility during

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

spring and summer. It is located at

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the ( hour circle of the) point in question above the earth. When pair ...

16^h 41.7^m,

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of th ...

+36° 28'. With 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 ...

of 5.8, it is barely visible with the

on clear nights. Its diameter is about 23 arcminutes and it is readily viewable in small telescopes. Nearby is

NGC 6207 NGC 6207 is a spiral galaxy located in the constellation Hercules. It is designated as SA(s)c in the galaxy morphological classification scheme and was discovered by William Herschel on 16 May 1787. NGC 6207 is located at about 30 million light-y ...

, a 12th-magnitude edge-on galaxy that lies 28 arcminutes directly northeast. A small galaxy, IC 4617, lies halfway between NGC 6207 and M13, north-northeast of the large globular cluster's center. In traditional binoculars, the Hercules Globular Cluster appears as a round patch of light. At least four inches of telescope aperture resolves stars in M13's outer extent as small pinpoints of light. However, only larger telescopes resolve stars further into the center of the cluster.

Characteristics

About 145

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distance, astronomical distances and is equivalent to about 9.46 Orders of magnitude (numbers)#1012, trillion kilometers (), or 5.88 ...

s in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid f ...

, M13 is composed of several hundred thousand

s, the brightest of which is a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around o ...

, the

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 e ...

V11, also known as V1554 Herculis, with an apparent visual magnitude of 11.95. M13 is 22,200–25,000 light-years away 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 sur ...

, and the globular cluster is one of over one hundred that orbit the center of the Milky Way. Single stars in this globular cluster were first resolved in 1779. Compared to the stars in the neighborhood of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, the stars of the M13 population are more than a hundred times more densely packed. They are so close together that they sometimes collide and produce new stars. The newly formed, young stars, so-called "

blue straggler A blue straggler is a main-sequence star in an open or globular cluster that is more luminous and bluer than stars at the main sequence turnoff point for the cluster. Blue stragglers were first discovered by Allan Sandage in 1953 while perform ...

s", are particularly interesting to astronomers. The 1974

Arecibo message The Arecibo message is an interstellar radio message carrying basic information about humanity and Earth that was sent to the globular cluster Messier 13 in 1974. It was meant as a demonstration of human technological achievement, rather than ...

, which contained encoded information about the human race, DNA, atomic numbers, Earth's position and other information, was beamed from the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science ...

radio telescope towards M13 as an experiment in contacting potential extraterrestrial civilizations in the cluster. The cluster will move through space during the transit time; opinions differ as to whether or not the cluster will be in a position to receive the message by the time that it arrives. The last two variables (V63 and V64) were discovered from Spain in April 2021 and March 2022 respectively.

Literary references

* The

science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel uni ...

novellas "

Sucker Bait ''Sucker Bait'' is a science fiction novella by American writer Isaac Asimov. It was first serialized in the February and March 1954 issues of ''Astounding Science Fiction'', and reprinted in the 1955 collection '' The Martian Way and Other Sto ...

" by

Isaac Asimov yi, יצחק אזימאװ , birth_date = , birth_place = Petrovichi, Russian SFSR , spouse = , relatives = , children = 2 , death_date = , death_place = Manhattan, New York City, U.S. , nationality = Russian (1920–1922)Soviet (192 ...

and the novel '' Question and Answer'' by

Poul Anderson Poul William Anderson (November 25, 1926 – July 31, 2001) was an American fantasy and science fiction author who was active from the 1940s until the 21st century. Anderson wrote also historical novels. His awards include seven Hugo Awards and ...

take place on Troas, a world within M13. * In the German science fiction series '' Perry Rhodan'', M13 is the location of Arkon, the homeworld of the race of Arkonides. * In author Dan Simmons' ''

Hyperion Cantos The ''Hyperion Cantos'' is a series of science fiction novels by Dan Simmons. The title was originally used for the collection of the first pair of books in the series, '' Hyperion'' and '' The Fall of Hyperion'', and later came to refer to t ...

'' the Hercules cluster is where a copy of Earth was secretly recreated after the original was destroyed. * In his novel ''

The Sirens of Titan ''The Sirens of Titan'' is a comic science fiction novel by Kurt Vonnegut Jr., first published in 1959. His second novel, it involves issues of free will, omniscience, and the overall purpose of human history. Much of the story revolves around ...

'',

Kurt Vonnegut Kurt Vonnegut Jr. (November 11, 1922 – April 11, 2007) was an American writer known for his satirical and darkly humorous novels. In a career spanning over 50 years, he published fourteen novels, three short-story collections, five plays, and ...

writes "Every passing hour brings the Solar System forty-three thousand miles closer to Globular Cluster M13 in Hercules—and still there are some misfits who insist that there is no such thing as progress." * Deliberately engineering a star in Messier 13 to go

nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramat ...

was part of the

Cybermen The Cybermen are a fictional race of cyborgs principally portrayed in the British science fiction television programme ''Doctor Who''. The Cybermen are a species of space-faring cyborgs who often forcefully and painfully convert human beings ( ...

's complicated plot in the 1968 ''

Doctor Who ''Doctor Who'' is a British science fiction television series broadcast by the BBC since 1963. The series depicts the adventures of a Time Lord called the Doctor, an extraterrestrial being who appears to be human. The Doctor explores the ...

'' story '' The Wheel in Space''. * In

Bill Amend William J. C. Amend III (; born September 20, 1962) is an American cartoonist. He is known for his comic strip '' FoxTrot''. Early life Amend was born in Massachusetts and raised in Northern California. He attended high school in Burlingame, ...

's popular comic strip ''

FoxTrot The foxtrot is a smooth, progressive dance characterized by long, continuous flowing movements across the dance floor. It is danced to big band (usually vocal) music. The dance is similar in its look to waltz, although the rhythm is in a tim ...

'', Jason Fox mentions observing the M13 Globular Cluster.

Gallery

File:Hercules constellation map.png, M13 is in "armpit" of Hercules constellation File:Heart of M13 Hercules Globular Cluster.jpg, Heart of the Hercules Globular Cluster, Hubble image File:Hubble’s Views of M13 (2010) and M3 (2019).jpg, Hubble Discovers Hydrogen-Burning White Dwarfs Enjoying Slow Ageing

References

External links

Messier 13, SEDS Messier pages

L199 (V63), a new variable star in M13

Variability of L261 in M13 (V64)

Messier 13, Galactic Globular Clusters Database page

* ttp://www.astrovox.gr/forum/album_pic.php?pic_id=16664 Messier 13, Amateur astrophotographer (hgg) photo using the 9.25" Celestron Telescope (85min exposure)
M13 Hercules Globular photo detail Dark Atmospheres

* ttps://ui.adsabs.harvard.edu/abs/2019AcA....69..101O/abstract Variable Stars in M13. III. The Cepheid Variables and their Relation to Evolutionary Changes in Metal-Poor BL Her Stars.
Messier 13, Image by Waid Observatory

NightSkyInfo.com – M13, the Hercules Globular Cluster

Photometric study of the V2 cepheid in M13

Period, Amplitude and Light Curve of V38 in M13

* * {{DEFAULTSORT:Messier 13 Messier 013 Messier 013

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Milky Way Messier 013 ?