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{{short description|Tip međuzvezdanog oblaka}}
'''Molekularni oblak''' je vrsta međuzvezdanog oblaka, gustine i veličine koji omogućavaju formiranje [[molekul]]a, najčešće molekularnog vodonika (H<sub>2</sub>). Ovo je u suprotnosti sa drugim oblastima međuzvezdanog prostora koji sadrže uglavnom jonizovani gas.
[[File:"Finger of God" Bok globule in the Carina Nebula.jpg|thumb|250px|Za nekoliko miliona godina svetlost sjajnih zvezda proključaće ovaj molekularni oblak gasa i prašine. Ovaj oblak se odlomio od [[NGC 3372|magline Carina]]. Novoformirane zvezde su vidljive u blizini, a njihove slike su pojačano crvene od plave svetlosti preferentno rasute prožimajućom prašinom. Ova slika pokriva oko dve svetlosne godine, a snimio ju je svemirski teleskop [[Hubble Space Telescope|Hubl]] 1999.]]


'''Molekularni oblak''', sometimes called a '''stellar nursery''' (if [[star formation]] is occurring within), vrsta je [[interstellar cloud|međuzvezdanog oblaka]], gustine i veličine koji omogućavaju formiranje [[molekul]]a, najčešće [[Водоник|molekularnog vodonika]] (-{H}-<sub>2</sub>). Ovo je u suprotnosti sa drugim oblastima međuzvezdanog prostora koji sadrže uglavnom [[Плазма (физика)|jonizovani gas]].
Molekularni vodonik je teško otkriti [[infracrvena svetlost|infracrvenim]] i radio talasima, tako da molekul koji se najčešće koristi za određivanje prisustva H<sub>2</sub> je [[ugljen-monoksid]] (CO) . Odnos CO [[luminiscencija|luminiscencije]] i H<sub>2</sub> mase smatra se konstantnim, mada postoje razlozi za sumnju ovu pretpostavku, zasnovani na posmatranju nekih drugih [[galaksija]].


Molekularni vodonik je teško otkriti [[infracrvena svetlost|infracrvenim]] i radio talasima, tako da molekul koji se najčešće koristi za određivanje prisustva -{H}-<sub>2</sub> je [[ugljen-monoksid]] (-{CO}-). Odnos -{CO}- [[luminiscencija|luminiscencije]] i -{H}-<sub>2</sub> mase smatra se konstantnim, mada postoje razlozi za sumnju ovu pretpostavku, zasnovani na posmatranju nekih drugih [[galaksija]].<ref>{{cite web | author=Craig Kulesa | title=Overview: Molecular Astrophysics and Star Formation | work=Research Projects | url=http://loke.as.arizona.edu/~ckulesa/research/overview.html | access-date=September 7, 2005 }}</ref>
{{klica-astronomija}}


Unutar molekularnih oblaka nalaze se regioni veće gustine, u kojima boravi puno prašine i mnogo jezgara plina, zvani nakupine. Ove nakupine su početak stvaranja zvezda ako su gravitacione sile dovoljne da izazovu kolaps prašine i gasa.<ref>{{Cite book|title=Astronomy|publisher=[[Rice University]]|year=2016|isbn=978-1938168284|url=https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Astronomy-Draft-20160817.pdf|pages=761|via=Open Stax}}</ref>

== Pojava ==
[[Image:Barnard 68.jpg|thumb|500pix.jpg|left|Molekularni oblak [[Barnard 68]], oko 500 svetlosnih godina udaljen i 0,5 svetlosnih godina u prečniku.]]
{{rut}}
Unutar [[Milky Way|Mlečnog puta]], molecular gas clouds account for less than one percent of the volume of the [[interstellar medium]] (ISM), yet it is also the densest part of the medium, comprising roughly half of the total gas mass interior to the [[Sun]]'s galactic orbit. The bulk of the molecular gas is contained in a ring between {{convert|3.5|and|7.5|kpc|ly|lk=on|abbr = off}} from the center of the Milky Way (the Sun is about 8.5 kiloparsecs from the center).<ref name="ferriere2001">{{cite journal | author=Ferriere, D. | title= The Interstellar Environment of our Galaxy | journal=Reviews of Modern Physics | date=2001| volume=73 | issue=4 | pages= 1031–1066 | doi = 10.1103/RevModPhys.73.1031 | bibcode=2001RvMP...73.1031F|arxiv = astro-ph/0106359 | s2cid= 16232084 }}</ref> Large scale CO maps of the galaxy show that the position of this gas correlates with the spiral arms of the galaxy.<ref>{{cite journal | author=Dame | title=A composite CO survey of the entire Milky Way | journal=Astrophysical Journal | date=1987| volume=322 | pages= 706–720 | doi = 10.1086/165766 | last2=Ungerechts | first2=H. | last3=Cohen | first3=R. S. | last4=De Geus | first4=E. J. | last5=Grenier | first5=I. A. | last6=May | first6=J. | last7=Murphy | first7=D. C. | last8=Nyman | first8=L.-A. | last9=Thaddeus | first9=P. | bibcode=1987ApJ...322..706D | hdl=1887/6534 | display-authors=1| url=https://openaccess.leidenuniv.nl/bitstream/handle/1887/6534/ApJ_322_706_720.pdf?sequence=1 }}</ref> That molecular gas occurs predominantly in the spiral arms suggests that molecular clouds must form and dissociate on a timescale shorter than 10 million years—the time it takes for material to pass through the arm region.<ref name="williams2000">{{cite conference | first1 = J. P. | last1 = Williams | last2 = Blitz | first2 = L. | last3 = McKee | first3 = C. F. | title = The Structure and Evolution of Molecular Clouds: from Clumps to Cores to the IMF | book-title = Protostars and Planets IV | pages = 97 | publisher = Tucson: University of Arizona Press | date = 2000 | arxiv = astro-ph/9902246 |bibcode = 2000prpl.conf...97W }}</ref>

[[File:Violent birth announcement from an infant star.jpg|thumb|Circinus molecular cloud has a mass around 250,000 times that of the Sun.<ref>{{cite news|title=Violent birth announcement from an infant star|url=http://www.spacetelescope.org/images/potw1421a/|access-date=27 May 2014|newspaper=ESA/Hubble Picture of the Week}}</ref>]]
Vertically to the plane of the galaxy, the molecular gas inhabits the narrow midplane of the galactic disc with a characteristic [[scale height]], ''Z'', of approximately 50 to 75 parsecs, much thinner than the warm [[atom]]ic (''Z ''from 130 to 400&nbsp;parsecs) and warm [[ion]]ized (''Z ''around 1000&nbsp;parsecs) gaseous [[Interstellar medium#Interstellar matter|components of the ISM]].<ref>{{cite journal | author=Cox, D. | date=2005 | title=The Three-Phase Interstellar Medium Revisited | journal=Annual Review of Astronomy and Astrophysics | volume=43 | issue=1 | pages=337–385 | doi=10.1146/annurev.astro.43.072103.150615 | bibcode=2005ARA&A..43..337C}}</ref> The exception to the ionized-gas distribution are [[H II region]]s, which are bubbles of hot ionized gas created in molecular clouds by the intense radiation given off by [[OB star|young massive stars]] and as such they have approximately the same vertical distribution as the molecular gas.

This distribution of molecular gas is averaged out over large distances; however, the small scale distribution of the gas is highly irregular with most of it concentrated in discrete clouds and cloud complexes.<ref name="ferriere2001" />

== Tipovi molekularnog oblaka ==

=== Gigantski molekulani oblaci ===
[[File:Part of the Taurus Molecular Cloud.jpg|thumb|Part of the Taurus Molecular Cloud.<ref>{{cite news|title=APEX Turns its Eye to Dark Clouds in Taurus|url=http://www.eso.org/public/news/eso1209/|access-date=17 February 2012|newspaper=ESO Press Release}}</ref>]]

A vast assemblage of molecular gas that has more than 10 thousand times the mass of the Sun<ref name="Fukui_Kawamura_2010">See, e.g., {{Cite journal | last1 = Fukui | first1 = Y. | last2 = Kawamura | first2 = A. | title = Molecular Clouds in Nearby Galaxies | doi = 10.1146/annurev-astro-081309-130854 | journal = The Annual Review of Astronomy and Astrophysics | volume = 48 | pages = 547–580 | year = 2010 | bibcode = 2010ARA&A..48..547F }}</ref> is called a '''giant molecular cloud''' ('''GMC'''). GMCs are around 15 to 600 light-years in diameter (5 to 200 parsecs) and typical masses of 10 thousand to 10 million solar masses.<ref name="murray">{{Cite journal | last1 = Murray | first1 = N. | title = Star Formation Efficiencies and Lifetimes of Giant Molecular Clouds in the Milky Way | doi = 10.1088/0004-637X/729/2/133 | journal = The Astrophysical Journal | volume = 729 | issue = 2 | pages = 133 | year = 2011 |arxiv = 1007.3270 |bibcode = 2011ApJ...729..133M | s2cid = 118627665 }}</ref> Whereas the average density in the solar vicinity is one particle per cubic centimetre, the average density of a GMC is a hundred to a thousand times as great. Although the Sun is much more dense than a GMC, the volume of a GMC is so great that it contains much more mass than the Sun. The substructure of a GMC is a complex pattern of filaments, sheets, bubbles, and irregular clumps.<ref name="williams2000" />

The densest parts of the filaments and clumps are called "molecular cores", while the densest molecular cores are called "dense molecular cores" and have densities in excess of 10<sup>4</sup> to 10<sup>6</sup> particles per cubic centimeter. Observationally, typical molecular cores are traced with CO and dense molecular cores are traced with [[ammonia]]. The concentration of [[Cosmic dust|dust]] within molecular cores is normally sufficient to block light from background stars so that they appear in silhouette as [[dark nebulae]].<ref name="francesco2006">{{cite conference | author = Di Francesco, J. |display-authors=etal | title = An Observational Perspective of Low-Mass Dense Cores I: Internal Physical and Chemical Properties| book-title = Protostars and Planets V | date = 2006 | arxiv = astro-ph/0602379 |bibcode = 2007prpl.conf...17D }}</ref>

GMCs are so large that "local" ones can cover a significant fraction of a constellation; thus they are often referred to by the name of that constellation, e.g. the [[Orion Molecular Cloud Complex|Orion Molecular Cloud]] (OMC) or the [[Taurus Molecular Cloud]] (TMC). These local GMCs are arrayed in a ring in the neighborhood of the Sun coinciding with the [[Gould Belt]].<ref>{{cite conference | author = Grenier| title = The Gould Belt, star formation, and the local interstellar medium| book-title = The Young Universe | date = 2004 | arxiv = astro-ph/0409096|bibcode = 2004astro.ph..9096G }} [https://arxiv.org/abs/astro-ph/0409096 Electronic preprint]</ref> The most massive collection of molecular clouds in the galaxy forms an asymmetrical ring about the galactic center at a radius of 120 parsecs; the largest component of this ring is the [[Sagittarius B2]] complex. The Sagittarius region is chemically rich and is often used as an exemplar by astronomers searching for new molecules in interstellar space.<ref>[http://www.mpifr-bonn.mpg.de/staff/epolehampton/thesis/node23.html Sagittarius B2 and its Line of Sight] {{webarchive|url=https://web.archive.org/web/20070312062920/http://www.mpifr-bonn.mpg.de/staff/epolehampton/thesis/node23.html |date=2007-03-12 }}</ref>[[File:Distribution of molecular gas in 30 merging galaxies.jpg|thumb|Distribution of molecular gas in 30 merging galaxies.<ref>{{cite web|title=Violent Origins of Disc Galaxies Probed by ALMA|url=http://www.eso.org/public/news/eso1429/|website=www.eso.org|publisher=[[European Southern Observatory]]|access-date=17 September 2014}}</ref>]]

=== Mali molekularni oblaci ===
{{main-lat|Bokove globule}}
Isolated gravitationally-bound small molecular clouds with masses less than a few hundred times that of the Sun are called [[Bok globule]]s. The densest parts of small molecular clouds are equivalent to the molecular cores found in GMCs and are often included in the same studies.

=== Visoko-latitudni difuzni molekulani oblaci ===
{{main-lat|Infracrveni cirus}}

In 1984 [[IRAS]] identified a new type of diffuse molecular cloud.<ref>{{cite journal | author=Low | title=Infrared cirrus – New components of the extended infrared emission | journal=Astrophysical Journal | date=1984| volume=278 | pages = L19 | doi = 10.1086/184213 | last2=Young | first2=E. | last3=Beintema | first3=D. A. | last4=Gautier | first4=T. N. | last5=Beichman | first5=C. A. | last6=Aumann | first6=H. H. | last7=Gillett | first7=F. C. | last8=Neugebauer | first8=G. | last9=Boggess | first9=N. | bibcode=1984ApJ...278L..19L | display-authors=1}}</ref> These were diffuse filamentary clouds that are visible at high [[Galactic coordinate system|galactic latitudes]]. These clouds have a typical density of 30 particles per cubic centimeter.<ref>{{cite journal | author=Gillmon, K. |author2=Shull, J.M. |name-list-style=amp | title= Molecular Hydrogen in Infrared Cirrus | journal=Astrophysical Journal | date=2006| volume=636 | pages= 908–915 | doi = 10.1086/498055 | bibcode=2006ApJ...636..908G|arxiv = astro-ph/0507587 | issue=2 |s2cid=18995587 }}</ref>

== Procesi ==
[[Image:Cepheus B.jpg|thumb|Young stars in and around molecular cloud [[Cepheus (constellation)|Cepheus]] B. Radiation from one bright, massive star is destroying the cloud (from top to bottom in this image) while simultaneously [[triggered star formation|triggering]] the formation of new stars.<ref>{{cite web|url=http://chandra.harvard.edu/photo/2009/cepb/|title=Chandra :: Photo Album :: Cepheus B :: August 12, 2009}}</ref>]]

=== Formiranje zvezda ===
{{Main-lat|Formiranje zvezda}}
The formation of [[star]]s occurs exclusively within molecular clouds. This is a natural consequence of their low temperatures and high densities, because the gravitational force acting to collapse the cloud must exceed the internal pressures that are acting "outward" to prevent a collapse. There is observed evidence that the large, star-forming clouds are confined to a large degree by their own gravity (like stars, planets, and galaxies) rather than by external pressure. The evidence comes from the fact that the "turbulent" velocities inferred from CO linewidth scale in the same manner as the orbital velocity (a [[virial theorem|virial]] relation).

=== Fizika ===
[[File:Serpens_south.jpg|thumb|Zvezdano jato [[Serpens South|Serpens Jug]] ugrađeno je u filamentarni molekularni oblak, viđen kao tamna vrpca koja prolazi vertikalno kroz klaster. Ovaj oblak služio je kao poligon za studije stabilnosti molekularnog oblaka.<ref name="FriesenBourke2016">{{cite journal|last1=Friesen|first1=R. K.|last2=Bourke|first2=T. L.|last3=Francesco|first3=J. Di|last4=Gutermuth|first4=R.|last5=Myers|first5=P. C.|title=The Fragmentation and Stability of Hierarchical Structure in Serpens South|journal=The Astrophysical Journal|volume=833|issue=2|year=2016|pages=204|issn=1538-4357|doi=10.3847/1538-4357/833/2/204|arxiv = 1610.10066 |bibcode = 2016ApJ...833..204F |s2cid=118594849}}</ref>]]

The physics of molecular clouds is poorly understood and much debated. Their internal motions are governed by [[turbulence]] in a cold, [[magnetism|magnetized]] gas, for which the turbulent motions are highly [[supersonic]] but comparable to the speeds of magnetic disturbances. This state is thought to lose energy rapidly, requiring either an overall collapse or a steady reinjection of energy. At the same time, the clouds are known to be disrupted by some process—most likely the effects of massive stars—before a significant fraction of their mass has become stars.

Molecular clouds, and especially GMCs, are often the home of [[Astrophysical maser|astronomical masers]].

== Reference ==
{{reflist|}}

== Literatura ==
{{refbegin|30em}}
* {{cite journal |last1=Gengel |first1=M.J. |last2=Larsen |first2=J. |last3=Van Ginneken |first3=M. |last4=Suttle |first4=M.D. |title=An urban collection of modern-day large micrometeorites: Evidence for variations in the extraterrestrial dust flux through the Quaternary |journal=Geology |volume=45 |issue=2 |pages=119 |date=December 1, 2016 |doi=10.1130/G38352.1 |bibcode = 2017Geo....45..119G |doi-access=free }}
* {{cite web |last=Chow |first=Denise |title=Discovery: Cosmic Dust Contains Organic Matter from Stars |url=http://www.space.com/13401-cosmic-star-dust-complex-organic-compounds.html |date=26 October 2011 |publisher=[[Space.com]] |access-date=2011-10-26 }}
* {{cite web |author=[[ScienceDaily]] Staff |title=Astronomers Discover Complex Organic Matter Exists Throughout the Universe |url=https://www.sciencedaily.com/releases/2011/10/111026143721.htm |date=26 October 2011 |publisher=[[ScienceDaily]] |access-date=2011-10-27 }}
* {{cite journal |last1=Kwok |first1=Sun |last2=Zhang |first2=Yong |title=Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features |date=26 October 2011 |journal=[[Nature (journal)|Nature]] |doi=10.1038/nature10542 |bibcode=2011Natur.479...80K |volume=479 |issue=7371 |pages=80–3 |pmid=22031328|s2cid=4419859 }}
* {{cite web |last1=Agle |first1=DC |last2=Brown |first2=Dwayne |last3=Jeffs |first3=William |title=Stardust Discovers Potential Interstellar Space Particles |url=http://www.jpl.nasa.gov/news/news.php?release=2014-278 |date=August 14, 2014 |work=[[NASA]] |access-date=August 14, 2014 }}
* {{cite news |last=Dunn |first=Marcia |title=Specks returned from space may be alien visitors |url=http://apnews.excite.com/article/20140814/us-sci--alien_stardust-9d21e5267a.html |date=August 14, 2014 |work=[[AP News]] |access-date=August 14, 2014 |archive-url=https://web.archive.org/web/20140819102935/http://apnews.excite.com/article/20140814/us-sci--alien_stardust-9d21e5267a.html |archive-date=August 19, 2014 |url-status=dead }}
* {{cite journal |last=Hand |first=Eric |title=Seven grains of interstellar dust reveal their secrets |url=http://news.sciencemag.org/space/2014/08/seven-grains-interstellar-dust-reveal-their-secrets |date=August 14, 2014 |journal=Science News |access-date=August 14, 2014 }}
* {{cite journal |author=Westphal, Andrew J.|title=Evidence for interstellar origin of seven dust particles collected by the Stardust spacecraft |date=August 15, 2014 |journal=[[Science (journal)|Science]] |volume=345 |number=6198 |pages=786–791 |doi=10.1126/science.1252496 |display-authors=etal|bibcode = 2014Sci...345..786W |pmid=25124433|hdl=2381/32470 |s2cid=206556225 |hdl-access=free }}

{{refend}}

== Spoljašnje veze ==
{{commons category-lat|Molecular clouds}}
* {{britannica|151690|Molecular cloud}}

{{Authority control-lat}}

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Верзија на датум 29. децембар 2020. у 06:54

Za nekoliko miliona godina svetlost sjajnih zvezda proključaće ovaj molekularni oblak gasa i prašine. Ovaj oblak se odlomio od magline Carina. Novoformirane zvezde su vidljive u blizini, a njihove slike su pojačano crvene od plave svetlosti preferentno rasute prožimajućom prašinom. Ova slika pokriva oko dve svetlosne godine, a snimio ju je svemirski teleskop Hubl 1999.

Molekularni oblak, sometimes called a stellar nursery (if star formation is occurring within), vrsta je međuzvezdanog oblaka, gustine i veličine koji omogućavaju formiranje molekula, najčešće molekularnog vodonika (H2). Ovo je u suprotnosti sa drugim oblastima međuzvezdanog prostora koji sadrže uglavnom jonizovani gas.

Molekularni vodonik je teško otkriti infracrvenim i radio talasima, tako da molekul koji se najčešće koristi za određivanje prisustva H2 je ugljen-monoksid (CO). Odnos CO luminiscencije i H2 mase smatra se konstantnim, mada postoje razlozi za sumnju ovu pretpostavku, zasnovani na posmatranju nekih drugih galaksija.[1]

Unutar molekularnih oblaka nalaze se regioni veće gustine, u kojima boravi puno prašine i mnogo jezgara plina, zvani nakupine. Ove nakupine su početak stvaranja zvezda ako su gravitacione sile dovoljne da izazovu kolaps prašine i gasa.[2]

Pojava

Molekularni oblak Barnard 68, oko 500 svetlosnih godina udaljen i 0,5 svetlosnih godina u prečniku.

Unutar Mlečnog puta, molecular gas clouds account for less than one percent of the volume of the interstellar medium (ISM), yet it is also the densest part of the medium, comprising roughly half of the total gas mass interior to the Sun's galactic orbit. The bulk of the molecular gas is contained in a ring between 35 and 75 kiloparsecs (110.000 and 240.000 light-years) from the center of the Milky Way (the Sun is about 8.5 kiloparsecs from the center).[3] Large scale CO maps of the galaxy show that the position of this gas correlates with the spiral arms of the galaxy.[4] That molecular gas occurs predominantly in the spiral arms suggests that molecular clouds must form and dissociate on a timescale shorter than 10 million years—the time it takes for material to pass through the arm region.[5]

Circinus molecular cloud has a mass around 250,000 times that of the Sun.[6]

Vertically to the plane of the galaxy, the molecular gas inhabits the narrow midplane of the galactic disc with a characteristic scale height, Z, of approximately 50 to 75 parsecs, much thinner than the warm atomic (Z from 130 to 400 parsecs) and warm ionized (Z around 1000 parsecs) gaseous components of the ISM.[7] The exception to the ionized-gas distribution are H II regions, which are bubbles of hot ionized gas created in molecular clouds by the intense radiation given off by young massive stars and as such they have approximately the same vertical distribution as the molecular gas.

This distribution of molecular gas is averaged out over large distances; however, the small scale distribution of the gas is highly irregular with most of it concentrated in discrete clouds and cloud complexes.[3]

Tipovi molekularnog oblaka

Gigantski molekulani oblaci

Part of the Taurus Molecular Cloud.[8]

A vast assemblage of molecular gas that has more than 10 thousand times the mass of the Sun[9] is called a giant molecular cloud (GMC). GMCs are around 15 to 600 light-years in diameter (5 to 200 parsecs) and typical masses of 10 thousand to 10 million solar masses.[10] Whereas the average density in the solar vicinity is one particle per cubic centimetre, the average density of a GMC is a hundred to a thousand times as great. Although the Sun is much more dense than a GMC, the volume of a GMC is so great that it contains much more mass than the Sun. The substructure of a GMC is a complex pattern of filaments, sheets, bubbles, and irregular clumps.[5]

The densest parts of the filaments and clumps are called "molecular cores", while the densest molecular cores are called "dense molecular cores" and have densities in excess of 104 to 106 particles per cubic centimeter. Observationally, typical molecular cores are traced with CO and dense molecular cores are traced with ammonia. The concentration of dust within molecular cores is normally sufficient to block light from background stars so that they appear in silhouette as dark nebulae.[11]

GMCs are so large that "local" ones can cover a significant fraction of a constellation; thus they are often referred to by the name of that constellation, e.g. the Orion Molecular Cloud (OMC) or the Taurus Molecular Cloud (TMC). These local GMCs are arrayed in a ring in the neighborhood of the Sun coinciding with the Gould Belt.[12] The most massive collection of molecular clouds in the galaxy forms an asymmetrical ring about the galactic center at a radius of 120 parsecs; the largest component of this ring is the Sagittarius B2 complex. The Sagittarius region is chemically rich and is often used as an exemplar by astronomers searching for new molecules in interstellar space.[13]

Distribution of molecular gas in 30 merging galaxies.[14]

Mali molekularni oblaci

Isolated gravitationally-bound small molecular clouds with masses less than a few hundred times that of the Sun are called Bok globules. The densest parts of small molecular clouds are equivalent to the molecular cores found in GMCs and are often included in the same studies.

Visoko-latitudni difuzni molekulani oblaci

In 1984 IRAS identified a new type of diffuse molecular cloud.[15] These were diffuse filamentary clouds that are visible at high galactic latitudes. These clouds have a typical density of 30 particles per cubic centimeter.[16]

Procesi

Young stars in and around molecular cloud Cepheus B. Radiation from one bright, massive star is destroying the cloud (from top to bottom in this image) while simultaneously triggering the formation of new stars.[17]

Formiranje zvezda

The formation of stars occurs exclusively within molecular clouds. This is a natural consequence of their low temperatures and high densities, because the gravitational force acting to collapse the cloud must exceed the internal pressures that are acting "outward" to prevent a collapse. There is observed evidence that the large, star-forming clouds are confined to a large degree by their own gravity (like stars, planets, and galaxies) rather than by external pressure. The evidence comes from the fact that the "turbulent" velocities inferred from CO linewidth scale in the same manner as the orbital velocity (a virial relation).

Fizika

Zvezdano jato Serpens Jug ugrađeno je u filamentarni molekularni oblak, viđen kao tamna vrpca koja prolazi vertikalno kroz klaster. Ovaj oblak služio je kao poligon za studije stabilnosti molekularnog oblaka.[18]

The physics of molecular clouds is poorly understood and much debated. Their internal motions are governed by turbulence in a cold, magnetized gas, for which the turbulent motions are highly supersonic but comparable to the speeds of magnetic disturbances. This state is thought to lose energy rapidly, requiring either an overall collapse or a steady reinjection of energy. At the same time, the clouds are known to be disrupted by some process—most likely the effects of massive stars—before a significant fraction of their mass has become stars.

Molecular clouds, and especially GMCs, are often the home of astronomical masers.

Reference

  1. ^ Craig Kulesa. „Overview: Molecular Astrophysics and Star Formation”. Research Projects. Приступљено 7. 9. 2005. 
  2. ^ Astronomy (PDF). Rice University. 2016. стр. 761. ISBN 978-1938168284 — преко Open Stax. 
  3. ^ а б Ferriere, D. (2001). „The Interstellar Environment of our Galaxy”. Reviews of Modern Physics. 73 (4): 1031—1066. Bibcode:2001RvMP...73.1031F. S2CID 16232084. arXiv:astro-ph/0106359Слободан приступ. doi:10.1103/RevModPhys.73.1031. 
  4. ^ Dame; et al. (1987). „A composite CO survey of the entire Milky Way” (PDF). Astrophysical Journal. 322: 706—720. Bibcode:1987ApJ...322..706D. doi:10.1086/165766. hdl:1887/6534. 
  5. ^ а б Williams, J. P.; Blitz, L.; McKee, C. F. (2000). „The Structure and Evolution of Molecular Clouds: from Clumps to Cores to the IMF”. Protostars and Planets IV. Tucson: University of Arizona Press. стр. 97. Bibcode:2000prpl.conf...97W. arXiv:astro-ph/9902246Слободан приступ. 
  6. ^ „Violent birth announcement from an infant star”. ESA/Hubble Picture of the Week. Приступљено 27. 5. 2014. 
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  11. ^ Di Francesco, J.; et al. (2006). „An Observational Perspective of Low-Mass Dense Cores I: Internal Physical and Chemical Properties”. Protostars and Planets V. Bibcode:2007prpl.conf...17D. arXiv:astro-ph/0602379Слободан приступ. 
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  13. ^ Sagittarius B2 and its Line of Sight Архивирано 2007-03-12 на сајту Wayback Machine
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  15. ^ Low; et al. (1984). „Infrared cirrus – New components of the extended infrared emission”. Astrophysical Journal. 278: L19. Bibcode:1984ApJ...278L..19L. doi:10.1086/184213. 
  16. ^ Gillmon, K.; Shull, J.M. (2006). „Molecular Hydrogen in Infrared Cirrus”. Astrophysical Journal. 636 (2): 908—915. Bibcode:2006ApJ...636..908G. S2CID 18995587. arXiv:astro-ph/0507587Слободан приступ. doi:10.1086/498055.  Непознати параметар |name-list-style= игнорисан (помоћ)
  17. ^ „Chandra :: Photo Album :: Cepheus B :: August 12, 2009”. 
  18. ^ Friesen, R. K.; Bourke, T. L.; Francesco, J. Di; Gutermuth, R.; Myers, P. C. (2016). „The Fragmentation and Stability of Hierarchical Structure in Serpens South”. The Astrophysical Journal. 833 (2): 204. Bibcode:2016ApJ...833..204F. ISSN 1538-4357. S2CID 118594849. arXiv:1610.10066Слободан приступ. doi:10.3847/1538-4357/833/2/204. 

Literatura

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