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Star cluster

March 08, 2023

Star clusters are large groups of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters are tight groups of ten thousand to millions of old stars which are gravitationally bound, while open clusters are more loosely clustered groups of stars, generally containing 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, Hyades, and 47 Tucanae.

Open cluster

Main article: Open cluster
 
The Pleiades, an open cluster dominated by hot blue stars surrounded by reflection nebulosity

Open clusters are very different from globular clusters. Unlike the spherically distributed globulars, they are confined to the galactic plane, and are almost always found within spiral arms. They are generally young objects, up to a few tens of millions of years old, with a few rare exceptions as old as a few billion years, such as Messier 67 (the closest and most observed old open cluster) for example.[1] They form H II regions such as the Orion Nebula.

Open clusters typically have a few hundred members and are located in an area up to 30 light-years across. Being much less densely populated than globular clusters, they are much less tightly gravitationally bound, and over time, are disrupted by the gravity of giant molecular clouds and other clusters. Close encounters between cluster members can also result in the ejection of stars, a process known as 'evaporation'.

The most prominent open clusters are the Pleiades and Hyades in Taurus. The Double Cluster of h+Chi Persei can also be prominent under dark skies. Open clusters are often dominated by hot young blue stars, because although such stars are short-lived in stellar terms, only lasting a few tens of millions of years, open clusters tend to have dispersed before these stars die.

Establishing precise distances to open clusters enables the calibration of the period-luminosity relationship shown by Cepheids variable stars, which are then used as standard candles. Cepheids are luminous and can be used to establish both the distances to remote galaxies and the expansion rate of the Universe (Hubble constant). Indeed, the open cluster NGC 7790 hosts three classical Cepheids which are critical for such efforts.[2][3]

Embedded cluster

Main article: Embedded cluster
 
The embedded Trapezium cluster seen in X-rays which penetrate the surrounding clouds
 
Star cluster NGC 3572 and its surroundings

Embedded clusters are groups of very young stars that are partially or fully encased in an Interstellar dust or gas which is often impervious to optical observations. Embedded clusters form in molecular clouds, when the clouds begin to collapse and form stars. There is often ongoing star formation in these clusters, so embedded clusters may be home to various types of young stellar objects including protostars and pre-main-sequence stars. An example of an embedded cluster is the Trapezium Cluster in the Orion Nebula. In ρ Ophiuchi cloud (L1688) core region there is an embedded cluster.[4]

The embedded cluster phase may last for several million years, after which gas in the cloud is depleted by star formation or dispersed through radiation pressure, stellar winds and outflows, or supernova explosions. In general less than 30% of cloud mass is converted to stars before the cloud is dispersed, but this fraction may be higher in particularly dense parts of the cloud. With the loss of mass in the cloud, the energy of the system is altered, often leading to the disruption of a star cluster. Most young embedded clusters disperse shortly after the end of star formation.[5]

The open clusters found in the Galaxy are former embedded clusters that were able to survive early cluster evolution. However, nearly all freely floating stars, including the Sun,[6] were originally born into embedded clusters that disintegrated.[5]

Globular cluster

Main article: Globular cluster
 
The globular cluster Messier 15 photographed by HST

Globular clusters are roughly spherical groupings of from 10 thousand to several million stars packed into regions of from 10 to 30 light-years across. They commonly consist of very old Population II stars – just a few hundred million years younger than the universe itself – which are mostly yellow and red, with masses less than two solar masses.[7] Such stars predominate within clusters because hotter and more massive stars have exploded as supernovae, or evolved through planetary nebula phases to end as white dwarfs. Yet a few rare blue stars exist in globulars, thought to be formed by stellar mergers in their dense inner regions; these stars are known as blue stragglers.

In the Milky Way galaxy, globular clusters are distributed roughly spherically in the galactic halo, around the Galactic Center, orbiting the center in highly elliptical orbits. In 1917, the astronomer Harlow Shapley made the first respectable estimate of the Sun's distance from the Galactic Center, based on the distribution of globular clusters.

Until the mid-1990s, globular clusters were the cause of a great mystery in astronomy, as theories of stellar evolution gave ages for the oldest members of globular clusters that were greater than the estimated age of the universe. However, greatly improved distance measurements to globular clusters using the Hipparcos satellite and increasingly accurate measurements of the Hubble constant resolved the paradox, giving an age for the universe of about 13 billion years and an age for the oldest stars of a few hundred million years less.

Our Galaxy has about 150 globular clusters,[7] some of which may have been captured cores of small galaxies stripped of stars previously in their outer margins by the tides of the Milky Way, as seems to be the case for the globular cluster M79. Some galaxies are much richer in globulars than the Milky Way: The giant elliptical galaxy M87 contains over a thousand.

A few of the brightest globular clusters are visible to the naked eye; the brightest, Omega Centauri, was observed in antiquity and catalogued as a star, before the telescopic age. The brightest globular cluster in the northern hemisphere is M13 in the constellation of Hercules.

Super star cluster

Main article: Super star cluster

Super star clusters are very large regions of recent star formation, and are thought to be the precursors of globular clusters. Examples include Westerlund 1 in the Milky Way.[8]

Intermediate forms

 
Messier 68, a loose globular cluster whose constituent stars span a volume of space more than a hundred light-years across

In 2005, astronomers discovered a new type of star cluster in the Andromeda Galaxy, which is, in several ways, very similar to globular clusters although less dense. No such clusters (which also known as extended globular clusters) are known in the Milky Way. The three discovered in Andromeda Galaxy are M31WFS C1[9] M31WFS C2, and M31WFS C3.

These new-found star clusters contain hundreds of thousands of stars, a similar number to globular clusters. The clusters also share other characteristics with globular clusters, e.g. the stellar populations and metallicity. What distinguishes them from the globular clusters is that they are much larger – several hundred light-years across – and hundreds of times less dense. The distances between the stars are thus much greater. The clusters have properties intermediate between globular clusters and dwarf spheroidal galaxies.[10]

How these clusters are formed is not yet known, but their formation might well be related to that of globular clusters. Why M31 has such clusters, while the Milky Way has not, is not yet known. It is also unknown if any other galaxy contains this kind of clusters, but it would be very unlikely that M31 is the sole galaxy with extended clusters.[10]

Another type of cluster are faint fuzzies which so far have only been found in lenticular galaxies like NGC 1023 and NGC 3384. They are characterized by their large size compared to globular clusters and a ringlike distribution around the centres of their host galaxies. As the latter they seem to be old objects.[11]

Astronomical significance

 
Artist's impression of an exoplanet orbiting a star in the cluster Messier 67[12]

Star clusters are important in many areas of astronomy. The reason behind this is that almost all the stars in old clusters were born at roughly the same time. Various properties of all the stars in a cluster are a function only of mass, and so stellar evolution theories rely on observations of open and globular clusters. This is primarily true for old globular clusters. In the case of young (age < 1Gyr) and intermediate-age (1 < age < 5 Gyr), factors such as age, mass, chemical compositions may also play vital roles. Based on their ages, star clusters can reveal a lot of information about their host galaxies. For example, star clusters residing in the Magellanic Clouds can provide essential information about the formation of the Magellanic Clouds dwarf galaxies. This, in turn, can help us understand many astrophysical processes happening in our own Milky Way Galaxy. These clusters, especially the young ones can explain the star formation process that might have happened in our Milky Way Galaxy.

Clusters are also a crucial step in determining the distance scale of the universe. A few of the nearest clusters are close enough for their distances to be measured using parallax. A Hertzsprung–Russell diagram can be plotted for these clusters which has absolute values known on the luminosity axis. Then, when similar diagram is plotted for a cluster whose distance is not known, the position of the main sequence can be compared to that of the first cluster and the distance estimated. This process is known as main-sequence fitting. Reddening and stellar populations must be accounted for when using this method.

Nearly all stars in the Galactic field, including the Sun, were initially born in regions with embedded clusters that disintegrated. This means that properties of stars and planetary systems may have been affected by early clustered environments. This appears to be the case for our own Solar System, in which chemical abundances point to the effects of a supernova from a nearby star early in our Solar System's history.

Star cloud

 
Scutum Star Cloud with open cluster Messier 11 at lower left

Technically not star clusters, star clouds are large groups of many stars within a galaxy, spread over very many light-years of space. Often they contain star clusters within them. The stars appear closely packed, but are not usually part of any structure.[13] Within the Milky Way, star clouds show through gaps between dust clouds of the Great Rift, allowing deeper views along our particular line of sight.[14] Star clouds have also been identified in other nearby galaxies.[15] Examples of star clouds include the Large Sagittarius Star Cloud, Small Sagittarius Star Cloud, Scutum Star Cloud, Cygnus Star Cloud, Norma Star Cloud, and NGC 206 in the Andromeda Galaxy.

Nomenclature

In 1979, the International Astronomical Union's 17th general assembly recommended that newly discovered star clusters, open or globular, within the Galaxy have designations following the convention "Chhmm±ddd", always beginning with the prefix C, where h, m, and d represent the approximate coordinates of the cluster centre in hours and minutes of right ascension, and degrees of declination, respectively, with leading zeros. The designation, once assigned, is not to change, even if subsequent measurements improve on the location of the cluster centre.[16] The first of such designations were assigned by Gosta Lynga in 1982.[17][18]

See also

 
Wikimedia Commons has media related to:
Star cluster (category)

References

  1. ^ Brent A. Archinal; Steven J. Hynes (2003). Star Clusters. Willmann-Bell. ISBN 978-0-943396-80-4.
  2. ^ Sandage, Allan (1958). "Cepheids in Galactic Clusters. I. CF Cass in NGC 7790". The Astrophysical Journal. 128: 150. Bibcode:1958ApJ...128..150S. doi:10.1086/146532.
  3. ^ Majaess, D.; Carraro, G.; Moni Bidin, C.; Bonatto, C.; Berdnikov, L.; Balam, D.; Moyano, M.; Gallo, L.; Turner, D.; Lane, D.; Gieren, W.; Borissova, J.; Kovtyukh, V.; Beletsky, Y. (2013). "Anchors for the cosmic distance scale: The Cepheids U Sagittarii, CF Cassiopeiae, and CEab Cassiopeiae". Astronomy & Astrophysics. 560: A22. arXiv:1311.0865. Bibcode:2013A&A...560A..22M. doi:10.1051/0004-6361/201322670. S2CID 55934597.
  4. ^ Greene, Thomas P; Meyer, Michael R (1995). "An Infrared Spectroscopic Survey of the rho Ophiuchi Young Stellar Cluster: Masses and Ages from the H-R Diagram". Astrophysical Journal. 450: 233. Bibcode:1995ApJ...450..233G. doi:10.1086/176134.
  5. ^ a b Lada, Charles J.; Lada, Elizabeth A. (2003). "Embedded Clusters in Molecular Clouds". Annual Review of Astronomy and Astrophysics. 41 (1): 57–115. arXiv:astro-ph/0301540. Bibcode:2003ARA&A..41...57L. doi:10.1146/annurev.astro.41.011802.094844. ISSN 0066-4146. S2CID 16752089.
  6. ^ Gounelle, M.; Meynet, G. (2012-08-27). "Solar system genealogy revealed by extinct short-lived radionuclides in meteorites". Astronomy & Astrophysics. EDP Sciences. 545: A4. arXiv:1208.5879. Bibcode:2012A&A...545A...4G. doi:10.1051/0004-6361/201219031. ISSN 0004-6361. S2CID 54970631.
  7. ^ a b Dinwiddie, Robert; Gater, Will; Sparrow, Giles; Stott, Carole (2012). Stars and Planets. Nature Guide. DK. pp. 14, 134–137. ISBN 978-0-7566-9040-3.
  8. ^ "Young and Exotic Stellar Zoo: ESO's Telescopes Uncover Super Star Cluster in the Milky Way". ESO. 2005-03-22. from the original on 2017-12-01. Retrieved 2017-11-27.
  9. ^ "@1592523". u-strasbg.fr. Retrieved 28 April 2018.
  10. ^ a b A. P. Huxor; N. R. Tanvir; M.J. Irwin; R. Ibata (2005). "A new population of extended, luminous, star clusters in the halo of M31". Monthly Notices of the Royal Astronomical Society. 360 (3): 993–1006. arXiv:astro-ph/0412223. Bibcode:2005MNRAS.360.1007H. doi:10.1111/j.1365-2966.2005.09086.x. S2CID 6215035.
  11. ^ A. Burkert; J. Brodie; S. Larsen 3 (2005). "Faint Fuzzies and the Formation of Lenticular Galaxies". The Astrophysical Journal. 628 (1): 231–235. arXiv:astro-ph/0504064. Bibcode:2005ApJ...628..231B. doi:10.1086/430698. S2CID 11466131.
  12. ^ "First Planet Found Around Solar Twin in Star Cluster". ESO Press Release. from the original on 2017-12-01. Retrieved 2017-11-27.
  13. ^ Patrick Moore (2005). The Observer's Year: 366 Nights in the Universe. Springer. p. 199. ISBN 1-85233-884-9.
  14. ^ Bob King (2016-07-13). "Paddle the Milky Way's Dark River". skyandtelescope.org. Retrieved 2020-09-29.
  15. ^ Bob King (2016-10-05). "Resolving Andromeda - How to See Stars 2.5 Million Light-Years Away". skyandtelescope.org. Retrieved 2020-09-20.
  16. ^ XVIIth General Assembly (PDF) (14–23 August 1979). Montreal, Canada: International Astronomical Union. Summer 1979. p. 13. (PDF) from the original on 18 January 2015. Retrieved 18 December 2014.
  17. ^ Lynga, G. (October 1982). "IAU numbers for some recently discovered clusters". Bulletin d'Information du Centre de Données Stellaires. 23: 89. Bibcode:1982BICDS..23...89L.
  18. ^ "Dictionary of Nomenclature of Celestial Objects". Simbad. Centre de données astronomiques de Strasbourg. 1 December 2014. from the original on 8 October 2014. Retrieved 21 December 2014.

External links

  • WEBDA open cluster database
  • NGC 2419 -Globular Cluster on SKY-MAP.ORG
  • Star Clusters, SEDS Messier pages
  • RG Research: Embedded Clusters
  • Star cluster - full article Encyclopædia Britannica,
  • Super Star Cluster Discovered in Our Own Milky Way
  • Probing the Birth of Super Star Clusters: Implications for Massive Star Formation, Kelsey E. Johnson, 2005
  • A new population of extended, luminous star clusters in the halo of M31, A.P. Huxor et al., 2004
  • HST/NICMOS Observations of the Embedded Cluster in NGC 2024: Constraints on the IMF and Binary Fraction, Wilson M. Liu et al., 2003
  • The Discovery of an Embedded Cluster of High-Mass Stars Near SGR 1900+14, Frederick J. Vrba et al., 2000

March 08, 2023
star, cluster, large, groups, stars, held, together, self, gravitation, main, types, star, clusters, distinguished, globular, clusters, tight, groups, thousand, millions, stars, which, gravitationally, bound, while, open, clusters, more, loosely, clustered, gr. Star clusters are large groups of stars held together by self gravitation Two main types of star clusters can be distinguished globular clusters are tight groups of ten thousand to millions of old stars which are gravitationally bound while open clusters are more loosely clustered groups of stars generally containing 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 Messier 92 a globular cluster in the constellation of Hercules Star clusters visible to the naked eye include the Pleiades Hyades and 47 Tucanae Contents 1 Open cluster 1 1 Embedded cluster 2 Globular cluster 3 Super star cluster 4 Intermediate forms 5 Astronomical significance 6 Star cloud 7 Nomenclature 8 See also 9 References 10 External linksOpen cluster EditMain article Open cluster The Pleiades an open cluster dominated by hot blue stars surrounded by reflection nebulosity Open clusters are very different from globular clusters Unlike the spherically distributed globulars they are confined to the galactic plane and are almost always found within spiral arms They are generally young objects up to a few tens of millions of years old with a few rare exceptions as old as a few billion years such as Messier 67 the closest and most observed old open cluster for example 1 They form H II regions such as the Orion Nebula Open clusters typically have a few hundred members and are located in an area up to 30 light years across Being much less densely populated than globular clusters they are much less tightly gravitationally bound and over time are disrupted by the gravity of giant molecular clouds and other clusters Close encounters between cluster members can also result in the ejection of stars a process known as evaporation The most prominent open clusters are the Pleiades and Hyades in Taurus The Double Cluster of h Chi Persei can also be prominent under dark skies Open clusters are often dominated by hot young blue stars because although such stars are short lived in stellar terms only lasting a few tens of millions of years open clusters tend to have dispersed before these stars die Establishing precise distances to open clusters enables the calibration of the period luminosity relationship shown by Cepheids variable stars which are then used as standard candles Cepheids are luminous and can be used to establish both the distances to remote galaxies and the expansion rate of the Universe Hubble constant Indeed the open cluster NGC 7790 hosts three classical Cepheids which are critical for such efforts 2 3 Embedded cluster Edit Main article Embedded cluster The embedded Trapezium cluster seen in X rays which penetrate the surrounding clouds Star cluster NGC 3572 and its surroundings Embedded clusters are groups of very young stars that are partially or fully encased in an Interstellar dust or gas which is often impervious to optical observations Embedded clusters form in molecular clouds when the clouds begin to collapse and form stars There is often ongoing star formation in these clusters so embedded clusters may be home to various types of young stellar objects including protostars and pre main sequence stars An example of an embedded cluster is the Trapezium Cluster in the Orion Nebula In r Ophiuchi cloud L1688 core region there is an embedded cluster 4 The embedded cluster phase may last for several million years after which gas in the cloud is depleted by star formation or dispersed through radiation pressure stellar winds and outflows or supernova explosions In general less than 30 of cloud mass is converted to stars before the cloud is dispersed but this fraction may be higher in particularly dense parts of the cloud With the loss of mass in the cloud the energy of the system is altered often leading to the disruption of a star cluster Most young embedded clusters disperse shortly after the end of star formation 5 The open clusters found in the Galaxy are former embedded clusters that were able to survive early cluster evolution However nearly all freely floating stars including the Sun 6 were originally born into embedded clusters that disintegrated 5 Globular cluster EditMain article Globular cluster The globular cluster Messier 15 photographed by HST Globular clusters are roughly spherical groupings of from 10 thousand to several million stars packed into regions of from 10 to 30 light years across They commonly consist of very old Population II stars just a few hundred million years younger than the universe itself which are mostly yellow and red with masses less than two solar masses 7 Such stars predominate within clusters because hotter and more massive stars have exploded as supernovae or evolved through planetary nebula phases to end as white dwarfs Yet a few rare blue stars exist in globulars thought to be formed by stellar mergers in their dense inner regions these stars are known as blue stragglers In the Milky Way galaxy globular clusters are distributed roughly spherically in the galactic halo around the Galactic Center orbiting the center in highly elliptical orbits In 1917 the astronomer Harlow Shapley made the first respectable estimate of the Sun s distance from the Galactic Center based on the distribution of globular clusters Until the mid 1990s globular clusters were the cause of a great mystery in astronomy as theories of stellar evolution gave ages for the oldest members of globular clusters that were greater than the estimated age of the universe However greatly improved distance measurements to globular clusters using the Hipparcos satellite and increasingly accurate measurements of the Hubble constant resolved the paradox giving an age for the universe of about 13 billion years and an age for the oldest stars of a few hundred million years less Our Galaxy has about 150 globular clusters 7 some of which may have been captured cores of small galaxies stripped of stars previously in their outer margins by the tides of the Milky Way as seems to be the case for the globular cluster M79 Some galaxies are much richer in globulars than the Milky Way The giant elliptical galaxy M87 contains over a thousand A few of the brightest globular clusters are visible to the naked eye the brightest Omega Centauri was observed in antiquity and catalogued as a star before the telescopic age The brightest globular cluster in the northern hemisphere is M13 in the constellation of Hercules Super star cluster EditMain article Super star cluster Super star clusters are very large regions of recent star formation and are thought to be the precursors of globular clusters Examples include Westerlund 1 in the Milky Way 8 Intermediate forms Edit Messier 68 a loose globular cluster whose constituent stars span a volume of space more than a hundred light years across In 2005 astronomers discovered a new type of star cluster in the Andromeda Galaxy which is in several ways very similar to globular clusters although less dense No such clusters which also known as extended globular clusters are known in the Milky Way The three discovered in Andromeda Galaxy are M31WFS C1 9 M31WFS C2 and M31WFS C3 These new found star clusters contain hundreds of thousands of stars a similar number to globular clusters The clusters also share other characteristics with globular clusters e g the stellar populations and metallicity What distinguishes them from the globular clusters is that they are much larger several hundred light years across and hundreds of times less dense The distances between the stars are thus much greater The clusters have properties intermediate between globular clusters and dwarf spheroidal galaxies 10 How these clusters are formed is not yet known but their formation might well be related to that of globular clusters Why M31 has such clusters while the Milky Way has not is not yet known It is also unknown if any other galaxy contains this kind of clusters but it would be very unlikely that M31 is the sole galaxy with extended clusters 10 Another type of cluster are faint fuzzies which so far have only been found in lenticular galaxies like NGC 1023 and NGC 3384 They are characterized by their large size compared to globular clusters and a ringlike distribution around the centres of their host galaxies As the latter they seem to be old objects 11 Astronomical significance EditThis section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Star cluster news newspapers books scholar JSTOR May 2021 Learn how and when to remove this template message Artist s impression of an exoplanet orbiting a star in the cluster Messier 67 12 Star clusters are important in many areas of astronomy The reason behind this is that almost all the stars in old clusters were born at roughly the same time Various properties of all the stars in a cluster are a function only of mass and so stellar evolution theories rely on observations of open and globular clusters This is primarily true for old globular clusters In the case of young age lt 1Gyr and intermediate age 1 lt age lt 5 Gyr factors such as age mass chemical compositions may also play vital roles Based on their ages star clusters can reveal a lot of information about their host galaxies For example star clusters residing in the Magellanic Clouds can provide essential information about the formation of the Magellanic Clouds dwarf galaxies This in turn can help us understand many astrophysical processes happening in our own Milky Way Galaxy These clusters especially the young ones can explain the star formation process that might have happened in our Milky Way Galaxy Clusters are also a crucial step in determining the distance scale of the universe A few of the nearest clusters are close enough for their distances to be measured using parallax A Hertzsprung Russell diagram can be plotted for these clusters which has absolute values known on the luminosity axis Then when similar diagram is plotted for a cluster whose distance is not known the position of the main sequence can be compared to that of the first cluster and the distance estimated This process is known as main sequence fitting Reddening and stellar populations must be accounted for when using this method Nearly all stars in the Galactic field including the Sun were initially born in regions with embedded clusters that disintegrated This means that properties of stars and planetary systems may have been affected by early clustered environments This appears to be the case for our own Solar System in which chemical abundances point to the effects of a supernova from a nearby star early in our Solar System s history Star cloud Edit Scutum Star Cloud with open cluster Messier 11 at lower left Technically not star clusters star clouds are large groups of many stars within a galaxy spread over very many light years of space Often they contain star clusters within them The stars appear closely packed but are not usually part of any structure 13 Within the Milky Way star clouds show through gaps between dust clouds of the Great Rift allowing deeper views along our particular line of sight 14 Star clouds have also been identified in other nearby galaxies 15 Examples of star clouds include the Large Sagittarius Star Cloud Small Sagittarius Star Cloud Scutum Star Cloud Cygnus Star Cloud Norma Star Cloud and NGC 206 in the Andromeda Galaxy Nomenclature EditIn 1979 the International Astronomical Union s 17th general assembly recommended that newly discovered star clusters open or globular within the Galaxy have designations following the convention Chhmm ddd always beginning with the prefix C where h m and d represent the approximate coordinates of the cluster centre in hours and minutes of right ascension and degrees of declination respectively with leading zeros The designation once assigned is not to change even if subsequent measurements improve on the location of the cluster centre 16 The first of such designations were assigned by Gosta Lynga in 1982 17 18 See also Edit Wikimedia Commons has media related to Star cluster category Hypercompact stellar system Robust associations of massive baryonic objects RAMBOs References Edit Brent A Archinal Steven J Hynes 2003 Star Clusters Willmann Bell ISBN 978 0 943396 80 4 Sandage Allan 1958 Cepheids in Galactic Clusters I CF Cass in NGC 7790 The Astrophysical Journal 128 150 Bibcode 1958ApJ 128 150S doi 10 1086 146532 Majaess D Carraro G Moni Bidin C Bonatto C Berdnikov L Balam D Moyano M Gallo L Turner D Lane D Gieren W Borissova J Kovtyukh V Beletsky Y 2013 Anchors for the cosmic distance scale The Cepheids U Sagittarii CF Cassiopeiae and CEab Cassiopeiae Astronomy amp Astrophysics 560 A22 arXiv 1311 0865 Bibcode 2013A amp A 560A 22M doi 10 1051 0004 6361 201322670 S2CID 55934597 Greene Thomas P Meyer Michael R 1995 An Infrared Spectroscopic Survey of the rho Ophiuchi Young Stellar Cluster Masses and Ages from the H R Diagram Astrophysical Journal 450 233 Bibcode 1995ApJ 450 233G doi 10 1086 176134 a b Lada Charles J Lada Elizabeth A 2003 Embedded Clusters in Molecular Clouds Annual Review of Astronomy and Astrophysics 41 1 57 115 arXiv astro ph 0301540 Bibcode 2003ARA amp A 41 57L doi 10 1146 annurev astro 41 011802 094844 ISSN 0066 4146 S2CID 16752089 Gounelle M Meynet G 2012 08 27 Solar system genealogy revealed by extinct short lived radionuclides in meteorites Astronomy amp Astrophysics EDP Sciences 545 A4 arXiv 1208 5879 Bibcode 2012A amp A 545A 4G doi 10 1051 0004 6361 201219031 ISSN 0004 6361 S2CID 54970631 a b Dinwiddie Robert Gater Will Sparrow Giles Stott Carole 2012 Stars and Planets Nature Guide DK pp 14 134 137 ISBN 978 0 7566 9040 3 Young and Exotic Stellar Zoo ESO s Telescopes Uncover Super Star Cluster in the Milky Way ESO 2005 03 22 Archived from the original on 2017 12 01 Retrieved 2017 11 27 1592523 u strasbg fr Retrieved 28 April 2018 a b A P Huxor N R Tanvir M J Irwin R Ibata 2005 A new population of extended luminous star clusters in the halo of M31 Monthly Notices of the Royal Astronomical Society 360 3 993 1006 arXiv astro ph 0412223 Bibcode 2005MNRAS 360 1007H doi 10 1111 j 1365 2966 2005 09086 x S2CID 6215035 A Burkert J Brodie S Larsen 3 2005 Faint Fuzzies and the Formation of Lenticular Galaxies The Astrophysical Journal 628 1 231 235 arXiv astro ph 0504064 Bibcode 2005ApJ 628 231B doi 10 1086 430698 S2CID 11466131 First Planet Found Around Solar Twin in Star Cluster ESO Press Release Archived from the original on 2017 12 01 Retrieved 2017 11 27 Patrick Moore 2005 The Observer s Year 366 Nights in the Universe Springer p 199 ISBN 1 85233 884 9 Bob King 2016 07 13 Paddle the Milky Way s Dark River skyandtelescope org Retrieved 2020 09 29 Bob King 2016 10 05 Resolving Andromeda How to See Stars 2 5 Million Light Years Away skyandtelescope org Retrieved 2020 09 20 XVIIth General Assembly PDF 14 23 August 1979 Montreal Canada International Astronomical Union Summer 1979 p 13 Archived PDF from the original on 18 January 2015 Retrieved 18 December 2014 Lynga G October 1982 IAU numbers for some recently discovered clusters Bulletin d Information du Centre de Donnees Stellaires 23 89 Bibcode 1982BICDS 23 89L Dictionary of Nomenclature of Celestial Objects Simbad Centre de donnees astronomiques de Strasbourg 1 December 2014 Archived from the original on 8 October 2014 Retrieved 21 December 2014 External links EditWEBDA open cluster database NGC 2419 Globular Cluster on SKY MAP ORG Star Clusters SEDS Messier pages RG Research Embedded Clusters Star cluster full article Encyclopaedia Britannica Super Star Cluster Discovered in Our Own Milky Way Probing the Birth of Super Star Clusters Implications for Massive Star Formation Kelsey E Johnson 2005 A new population of extended luminous star clusters in the halo of M31 A P Huxor et al 2004 HST NICMOS Observations of the Embedded Cluster in NGC 2024 Constraints on the IMF and Binary Fraction Wilson M Liu et al 2003 The Discovery of an Embedded Cluster of High Mass Stars Near SGR 1900 14 Frederick J Vrba et al 2000 Portals Physics Astronomy Stars Spaceflight Outer space Solar System Retrieved from https en wikipedia org w index php title Star cluster amp oldid 1140171492, wikipedia, wiki, book, books, library,

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