Messier 15

Messier 15 or M15 (also designated NGC 7078) is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. At an estimated 12.0 billion years old, it is one of the oldest known globular clusters.

Messier 15
New Hubble image of star cluster Messier 15
M15 photographed by HST. The planetary nebula Pease 1 can be seen as a small blue object to the upper left of the core of the cluster.
Observation data (J2000 epoch)
Right ascension 21h 29m 58.33s[2]
Declination+12° 10′ 01.2″[2]
Distance33 kly (10 kpc)[3]
Apparent magnitude (V)+6.2
Apparent dimensions (V)18′.0
Physical characteristics
Mass5.6×105[4] M
Radius~88 ly[5]
Metallicity = –2.37[6] dex
Estimated age12.0 Gyr[7]
Notable featuressteep central cusp
Other designationsNGC 7078, GCl 120[8]


M 15 is about 33,600 light-years from Earth, and 175 light-years in diameter.[9] It has an absolute magnitude of −9.2, which translates to a total luminosity of 360,000 times that of the Sun. Messier 15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as "core collapse" and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.[10]

Home to over 100,000 stars,[9] the cluster is notable for containing a large number of variable stars (112) and pulsars (8), including one double neutron star system, M15-C. It also contains Pease 1, the first planetary nebula discovered within a globular cluster in 1928.[11] Just three others have been found in globular clusters since then.[12]

Amateur astronomy

At magnitude 6.2, M15 approaches naked eye visibility under good conditions and can be observed with binoculars or a small telescope, appearing as a fuzzy star.[9] Telescopes with a larger aperture (at least 6 in./150 mm diameter) will start to reveal individual stars, the brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size.[9]

X-ray sources

Earth-orbiting satellites Uhuru and Chandra X-ray Observatory have detected two bright X-ray sources in this cluster: Messier 15 X-1 (4U 2129+12) and Messier 15 X-2.[13][14] The former appears to be the first astronomical X-ray source detected in Pegasus.


M15 core lucky 10pc

The central square arcminute of M15 imaged using the lucky imaging technique


Messier 15 with amateur telescope


Map showing the location of M15

M15 Globular Cluster from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block

Deep Broadband (RGB) image of M15 from the Mount Lemmon SkyCenter

See also


  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.
  3. ^ Hessels, J. W. T.; et al. (November 2007). "A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters". The Astrophysical Journal. 670 (1): 363–378. arXiv:0707.1602. Bibcode:2007ApJ...670..363H. doi:10.1086/521780.
  4. ^ Marks, Michael; Kroupa, Pavel (August 2010). "Initial conditions for globular clusters and assembly of the old globular cluster population of the Milky Way". Monthly Notices of the Royal Astronomical Society. 406 (3): 2000–2012. arXiv:1004.2255. Bibcode:2010MNRAS.406.2000M. doi:10.1111/j.1365-2966.2010.16813.x. Mass is from MPD on Table 1.
  5. ^ distance × sin( diameter_angle / 2 ) = 88 ly radius
  6. ^ 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.
  7. ^ Koleva, M.; et al. (April 2008). "Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting". Monthly Notices of the Royal Astronomical Society. 385 (4): 1998–2010. arXiv:0801.0871. Bibcode:2008MNRAS.385.1998K. doi:10.1111/j.1365-2966.2008.12908.x
  8. ^ "M 15". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
  9. ^ a b c d "M 15". astropix.
  10. ^ Gerssen J, van der Marel RP, Gebhardt K, Guhathakurta P, Peterson RC, Pryor C (2003). "Evidence for an intermediate-mass black hole in the globular cluster M 15. II. Kinematic analysis and dynamical modeling" (PDF). Astronomical Journal. Hubble Space Telescope. 125 (1): 376–377. arXiv:astro-ph/0210158. Bibcode:2003AJ....125..376G. doi:10.1086/345574.
  11. ^ Cohen, J.G.; Gillett, F.C. (1989). "The peculiar planetary nebula in M 22". Astrophysical Journal. 346: 803–807. Bibcode:1989ApJ...346..803C. doi:10.1086/168061.
  12. ^ "more". Messier 15.
  13. ^ Forman W; Jones C; Cominsky L; Julien P; Murray S; Peters G (1978). "The fourth Uhuru catalog of X-ray sources". Astrophysical Journal Supplement Series. 38: 357. Bibcode:1978ApJS...38..357F. doi:10.1086/190561.
  14. ^ White NE; Angelini L (2001). "The discovery of a second luminous low-mass X-ray binary in the globular cluster M15". Astrophysical Journal Letters. 561 (1): L101–5. arXiv:astro-ph/0109359. Bibcode:2001ApJ...561L.101W. doi:10.1086/324561.

External links

Coordinates: Sky map 21h 29m 58.38s, 12° 10′ 00.6″

1982–83 Edmonton Oilers season

The 1982–83 Edmonton Oilers season was the Oilers' fourth season in the National Hockey League (NHL) and their second-straight season of finishing with over 100 points, and they won the Smythe Division for the second straight season. The Oilers broke the NHL record for goals in a season with 424, breaking the record they set in the previous season.

1983 Stanley Cup Finals

The 1983 Stanley Cup Finals was the championship series of the National Hockey League's (NHL) 1982–83 season, and the culmination of the 1983 Stanley Cup playoffs. It was contested by the Edmonton Oilers in their first-ever Finals appearance and the defending champion New York Islanders, in their fourth consecutive and overall Finals appearance. The Islanders won the best-of-seven series, four games to none, to win their fourth consecutive and overall Stanley Cup championship.

It was also the fourth straight Finals of post-1967 expansion teams, and the first involving a former World Hockey Association (WHA) team. This is also the most recent time that a defending Stanley Cup champion has won the cup four years in a row, and also the first (and, to date, only) time a North American professional sports team has won four consecutive titles in any league competition with more than 20 teams. Since 1983, no professional sports team on the continent has won four consecutive championships and no NHL team has won more than two consecutive championships (most recently the Pittsburgh Penguins in 2016 and 2017). This would be the first of eight consecutive Finals contested by a team from Alberta (of which the Oilers played in six and the Calgary Flames in two). Although it was not the first Stanley Cup Finals to be contested by an Albertan team (the 1923 and 1924 Finals had been contested by teams from Edmonton and Calgary respectively), 1983 saw the first Finals games played in Alberta.

The Oilers would credit the Islanders' subdued post-series locker room celebration—focused more on putting ice packs on their various injuries—as teaching them the level of sacrifice and dedication needed to be champions. The Oilers would go on to win four Stanley Cups in the next five seasons—and five overall by 1990.

1983 Stanley Cup playoffs

The 1983 Stanley Cup playoffs, the championship of the National Hockey League (NHL) began on April 5, after the conclusion of the 1982–83 NHL season. The playoffs concluded on May 17 with the champion New York Islanders defeating the Edmonton Oilers 4–0 to win the Final series four games to none and win the Stanley Cup for the fourth consecutive season.

The 1983 Playoffs marked the first time that seven NHL teams based in Canada (Montreal, Toronto, Vancouver, Edmonton, Quebec, Winnipeg, and Calgary) all qualified for the playoffs in the same season. Since the 1967–68 expansion, all the Canadian teams have qualified for the playoffs on five other occasions – 1969 (Montreal and Toronto), 1975, 1976 and 1979 (Montreal, Toronto and Vancouver), and 1986 (the same seven as in 1983), the last time to date (as of 2018) that all active Canadian teams qualified. This is also the most recent time that the Toronto Maple Leafs and the Detroit Red Wings missed the playoffs in the same season.

In the Wales Conference, the Patrick Division champion Philadelphia Flyers were upset by the New York Rangers in the first round. The defending champion Islanders had qualified second in the Patrick Division, and defeated the Washington Capitals in the first round, and defeated the Rangers to qualify for the Conference Final. In the Adams Division, the first-place Boston Bruins defeated the Quebec Nordiques and the Buffalo Sabres (who swept the Canadiens in their opening round series) to advance to the Conference Final. In the Conference Final, the Islanders defeated Boston in six games to qualify for their fourth consecutive Cup Finals appearance.

In the Campbell Conference, the Smythe Division first seed Edmonton Oilers swept the Winnipeg Jets in the opening round, and defeated the Calgary Flames (who defeated the Vancouver Canucks three games to one in the opening round) in the Smythe Final. The Norris Champion Chicago Black Hawks defeated the St. Louis Blues three games to one and the Minnesota North Stars (who defeated the Toronto Maple Leafs three games to one in the opening round) in the Norris Final four games to one. Edmonton defeated the Norris Division champion Chicago Black Hawks in a four-game sweep in the Conference Final to advance to the Cup Final.

1987 NCAA Division I Men's Ice Hockey Tournament

The 1987 NCAA Men's Division I Ice Hockey Tournament was the culmination of the 1986–87 NCAA Division I men's ice hockey season, the 40th such tournament in NCAA history. It was held between March 20 and 28, 1987, and concluded with North Dakota defeating Michigan State 5-3. All Quarterfinals matchups were held at home team venues while all succeeding games were played at the Joe Louis Arena in Detroit, Michigan.

1996–97 New York Rangers season

The 1996–97 New York Rangers season was the Rangers' 71st season. The highlight of the season was that it was Wayne Gretzky's first season in New York.

The Rangers qualified for the playoffs as the fifth seed in the Eastern Conference, and advanced all the way to the Eastern Conference Finals, where they were defeated by the Philadelphia Flyers. This marked the last playoff appearance for the Rangers until the 2005–06 season.

35th National Hockey League All-Star Game

The 35th National Hockey League All-Star Game was held on February 8, 1983, at the Nassau Veterans Memorial Coliseum in Uniondale, New York, home to the New York Islanders. In the game, Edmonton Oilers' centre Wayne Gretzky set an All-Star Game record by scoring all of his four goals in the third period. Gretzky's four goal performance was instrumental in winning his first All-Star M.V.P. honor. Wayne Gretzky's Edmonton Oilers' linemate Mark Messier assisted on three of the four goals in the third period to set an All-Star Game record for most assists in a period.

Idaho Falls Chukars

The Idaho Falls Chukars are a professional baseball club based in Idaho Falls, Idaho. The Chukars are a Minor League Baseball affiliate of the Kansas City Royals. They play their home games at Melaleuca Field, which has a seating capacity of 3,600. The dimensions of the ballpark are 350' to left field, 390' to center field, and 335' to right field. The playing surface is natural grass (Kentucky bluegrass).The team plays in the Pioneer League, a short-season league operating from June to early September, which is designated as Rookie Advanced League. They adopted the name the Chukars following a fan vote when the major league affiliation changed after the 2003 season. A chukar is a game bird found in the region. The Chukars are the only professional sports team in Eastern Idaho and have one of the most loyal fanbases in the Pioneer League.

Kansas City Royals minor league players

Below is a partial list of minor league baseball players in the Kansas City Royals system.

List of astronomical catalogues

An astronomical catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. Astronomical catalogs are usually the result of an astronomical survey of some kind.

List of black holes

This is a list of black holes (and stars considered probable candidates) organized by size (including black holes of undetermined mass); some items in this list are galaxies or star clusters that are believed to be organized around a black hole. Messier and New General Catalogue designations are given where possible.

Messier object

The Messier objects are a set of 110 astronomical objects cataloged 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 interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.

The catalogue includes some astronomical objects that can be observed from Earth's Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in the Memoirs of the French Academy of Sciences in 1771,

and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's.

By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.

However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.

National Hockey League All-Star Game

The National Hockey League All-Star Game (French: Match des Étoiles de la Ligue Nationale de Hockey) is an exhibition ice hockey game that is traditionally held during the regular season of the National Hockey League (NHL), with many of the League's star players playing against each other. Each team plays with four players. The Game's proceeds benefit the pension fund of the players.

The NHL All-Star Game, held in late January or early February, marks the symbolic halfway point in the regular season, though not the mathematical halfway point which, for most seasons, is usually one or two weeks earlier. Since 2007, it is held in late January.

Pease 1

Pease 1 is a planetary nebula located within the globular cluster M15 33,600 light years away in the constellation Pegasus. It was the first planetary nebula known to exist within a globular cluster when it was discovered in 1928 (for Francis G. Pease), and just four more have been found (in other clusters) since. At magnitude 15.5, it requires telescopes with an aperture of at least 300-millimetre (12 in) to be detected.

Pioneer League rosters

Below are the full rosters and coaching staff of the eight Pioneer League teams.

Planetary nebula

A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.The term "planetary nebula" is arguably a misnomer because they are unrelated to planets or exoplanets. The true origin of the term was likely derived from the planet-like round shape of these nebulae as observed by astronomers through early telescopes, and although the terminology is inaccurate, it is still used by astronomers today. The first usage may have occurred during the 1780s with the English astronomer William Herschel who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, "... very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet."All planetary nebulae form at the end of intermediate massed star's lifetimes. They are a relatively short-lived phenomenon, lasting perhaps a few tens of thousands of years, compared to considerably longer phases of stellar evolution. Once all of the red giant's atmosphere has been dissipated, energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (PNN), ionizes the ejected material. Absorbed ultraviolet light then energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

Planetary nebulae likely play a crucial role in the chemical evolution of the Milky Way by expelling elements into the interstellar medium from stars where those elements were created. Planetary nebulae are observed in more distant galaxies, yielding useful information about their chemical abundances.

Starting from the 1990s, Hubble Space Telescope images revealed that many planetary nebulae have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms that produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.

Shapley–Sawyer Concentration Class

The Shapley–Sawyer Concentration Class is a classification system on a scale of one to twelve using Roman numerals for globular clusters according to their concentration. The most highly concentrated clusters such as M75 are classified as Class I, with successively diminishing concentrations ranging to Class XII, such as Palomar 12. (The class is sometimes given with numbers [Class 1–12] rather than with Roman numerals.)

Star cluster

Star clusters are very large groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds to millions of old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain fewer than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a moving group.

Star clusters visible to the naked eye include the Pleiades (M45), Hyades, and the Beehive Cluster (M44).

Timeline of epochs in cosmology

The timeline of cosmological epochs outlines the formation and subsequent evolution of the Universe from the Big Bang (13.799 ± 0.021 billion years ago) to the present day. An epoch is a moment in time from which nature or situations change to such a degree that it marks the beginning of a new era or age.

Times on this list are measured from the moment of the Big Bang.

See also

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