Editing Protoplanetary disk

{{Distinguish|Protoplanetary nebula}}
{{Short description|Gas and dust surrounding a newly formed star}}
[[File:HL Tau protoplanetary disk.jpg|thumb|[[Atacama Large Millimeter Array]] image of [[HL Tauri]]<ref>{{cite web|url=https://www.bbc.co.uk/news/science-environment-29932609|title=Planet formation captured in photo|publisher=[[BBC]]|date=2014-11-06|author=Johnathan Webb}}</ref><ref>{{cite web|url=https://public.nrao.edu/static/pr/planet-formation-alma.html|title=Birth of Planets Revealed in Astonishing Detail in ALMA's 'Best Image Ever'|publisher=NRAO|date=2014-11-06|url-status=dead|archive-url=https://web.archive.org/web/20141106220622/https://public.nrao.edu/static/pr/planet-formation-alma.html|archive-date=2014-11-06}}</ref>]]

A '''protoplanetary disk''' is a rotating [[circumstellar disc]] of dense gas and dust surrounding a [[stellar evolution|young newly formed]]  star, a [[T Tauri star]], or [[Herbig Ae/Be star]]. The protoplanetary disk may not be considered an [[accretion disk]]; while the two are similar, an accretion disk is hotter and spins much faster; it is also found on [[Black hole|black holes]], not stars. This process should not be confused with the accretion process thought to build up the planets themselves. Externally illuminated photo-evaporating protoplanetary disks are called [[proplyds]].

==Formation==
[[File:The evolutionary sequence of protoplanetary disks with substructures.png|thumb|The evolutionary sequence of protoplanetary disks with substructures<ref>{{cite web |title=Early Evolution of Planetary Disk Structures Seen for the First Time |url=https://public.nrao.edu/news/early-evolution-of-planetary-disk-structures-seen-for-the-first-time/ |website=National Radio Astronomy Observatory |access-date=18 February 2024}}</ref>]]
[[Image:Mamajek09 diskfraction.jpg|thumb|A 2009 image showing fractions of stars that suggest some evidence of having a protoplanetary disk as a function of their stellar age in millions of years; The samples are nearby young clusters and associations.<ref>{{cite journal|title=Initial Conditions of Planet Formation: Lifetimes of Primordial Disks|author=Mamajek, E.E.|date=2009|journal=AIP Conference Proceedings|volume=1158|pages=3–10|bibcode=2009AIPC.1158....3M|doi=10.1063/1.3215910|last2=Usuda|first2=Tomonori|last3=Tamura|first3=Motohide|last4=Ishii|first4=Miki|arxiv = 0906.5011 |s2cid=16660243}}</ref>]]
[[Protostar]]s form from [[molecular cloud]]s consisting primarily of [[molecular hydrogen]]. When a portion of a molecular cloud reaches a critical size, [[Jeans mass|mass]], or density, it begins to collapse under its own [[gravity]]. As this collapsing cloud, called a [[solar nebula]], becomes denser, random gas motions originally present in the cloud average out in favor of the direction of the nebula's net angular momentum. [[Conservation of angular momentum]] causes the rotation to increase as the nebula radius decreases. This rotation causes the cloud to flatten out—much like forming a flat pizza out of dough—and take the form of a disk. This occurs because [[centripetal acceleration]] from the orbital motion resists the gravitational pull of the star only in the radial direction, but the cloud remains free to collapse in the axial direction. The outcome is the formation of a thin disc supported by gas pressure in the axial direction.<ref>{{cite journal|title=Accretion discs in astrophysics|author=Pringle, J.E.|date=1981|journal=[[Annual Review of Astronomy and Astrophysics]]|volume=19|pages=137–162|bibcode=1981ARA&A..19..137P|doi=10.1146/annurev.aa.19.090181.001033}}</ref> The initial collapse takes about 100,000 years. After that time the star reaches a surface temperature similar to that of a main sequence star of the same mass and becomes visible.

It is now a T Tauri star. Accretion of gas onto the star continues for another 10 million years,<ref>{{cite journal | bibcode=2004ApJ...612..496M | author=Mamajek, E.E. | author2=Meyer, M.R. | author3=Hinz, P.M. | author4=Hoffmann, W.F. | author5=Cohen, M. | author6=Hora, J.L. | name-list-style=amp | title= Constraining the Lifetime of Circumstellar Disks in the Terrestrial Planet Zone: A Mid-Infrared Survey of the 30 Myr old Tucana-Horologium Association | journal= The Astrophysical Journal|volume=612 | issue=1 | date=2004 | pages= 496–510 | doi= 10.1086/422550 |arxiv = astro-ph/0405271 | s2cid=16366683 }}</ref> before the disk disappears, perhaps being blown away by the young star's [[stellar wind]], or perhaps simply ceasing to emit radiation after accretion has ended. The oldest protoplanetary disk yet discovered is 25 million years old.<ref>{{cite journal | bibcode=2005ApJ...621L..65W | author=White, R.J. | author2=Hillenbrand, L.A. | name-list-style=amp| title= A Long-lived Accretion Disk around a Lithium-depleted Binary T Tauri Star | journal= The Astrophysical Journal|volume=621 | issue=1 | date=2005 | pages= L65–L68| doi= 10.1086/428752 |arxiv = astro-ph/0501307 | s2cid=17532904 }}</ref><ref>{{cite web|url=http://www.universetoday.com/10795/audio-planetary-disk-that-refuses-to-grow-up/|title=Planetary Disk That Refuses to Grow Up (Interview with Lee Hartmann about the discovery)|last1=Cain|first1=Fraser|last2=Hartmann|first2=Lee|publisher=[[Universe Today]]|date=3 August 2005|access-date=1 June 2013}}</ref>

[[File:Protoplanetary Disk Simulated Spiral Arm vs Observational Data.jpg|thumb|Protoplanetary disk. Simulated spiral arm vs observational data.<ref>{{cite web|title=Protoplanetary Disk: Simulated Spiral Arm vs. Observational Data|url=http://www.spacetelescope.org/images/opo1540a/|access-date=30 October 2015}}</ref>]]

Protoplanetary disks around T Tauri stars differ from the disks surrounding the primary components of close binary systems with respect to their size and temperature. Protoplanetary disks have radii up to 1000 [[astronomical unit|AU]], and only their innermost parts reach temperatures above 1000 [[kelvin|K]]. They are very often accompanied by [[stellar jet|jets]].

Protoplanetary disks have been observed around several young stars in our galaxy. Observations by the [[Hubble Space Telescope]] have shown proplyds and planetary disks to be forming within the [[Orion Nebula]].<ref name="RicciRobberto2008">{{cite journal|last1=Ricci|first1=L.|last2=Robberto|first2=M.|last3=Soderblom|first3=D. R.|title=Thehubble Space Telescope/Advanced Camera for Surveys Atlas of Protoplanetary Disks in the Great Orion Nebula|journal=The Astronomical Journal|volume=136|issue=5|year=2008|pages=2136–2151|issn=0004-6256|doi=10.1088/0004-6256/136/5/2136|bibcode=2008AJ....136.2136R|s2cid=123470043 |doi-access=}}</ref><ref name="O'dellWong1996">{{cite journal|last1=O'dell|first1=C. R.|last2=Wong|first2=Kwan|title=Hubble Space Telescope Mapping of the Orion Nebula. I. A Survey of Stars and Compact Objects|journal=The Astronomical Journal|volume=111|year=1996|pages=846|issn=0004-6256|doi=10.1086/117832|bibcode=1996AJ....111..846O|doi-access=free}}</ref>

Protoplanetary disks are thought to be thin structures, with a typical vertical height much smaller than the radius, and a typical mass much smaller than the central young star.<ref>{{cite journal|last1=Armitage|first1=Philip J.|title=Dynamics of Protoplanetary Disks|journal=[[Annual Review of Astronomy and Astrophysics]]|date=2011|volume=49|issue=1|pages=195–236|doi=10.1146/annurev-astro-081710-102521|arxiv = 1011.1496 |bibcode = 2011ARA&A..49..195A |s2cid=55900935}}</ref>

The mass of a typical proto-planetary disk is dominated by its gas, however, the presence of dust grains has a major role in its evolution. Dust grains shield the mid-plane of the disk from energetic radiation from outer space that creates a dead zone in which the [[magnetorotational instability]] (MRI) no longer operates.<ref>{{cite journal|last1=Balbus|first1=Steven A.|last2=Hawley|first2=John F.|title=A powerful local shear instability in weakly magnetized disks. I - Linear analysis. II - Nonlinear evolution|journal=Astrophysical Journal|date=1991|volume=376|pages=214–233|doi=10.1086/170270|bibcode=1991ApJ...376..214B|url=https://articles.adsabs.harvard.edu/pdf/1991ApJ...376..223H|url-status=live|archiveurl=
https://web.archive.org/web/20201202075258/https://articles.adsabs.harvard.edu/pdf/1991ApJ...376..214B|archivedate=2020-12-02}}</ref><ref name="Layered Accretion In T Tauri Disks">{{cite journal|last1=Gammie|first1=Charles|title=Layered Accretion In T Tauri Disks|journal=Astrophysical Journal|date=1996|volume=457|page=355|doi=10.1086/176735|bibcode=1996ApJ...457..355G|url=https://articles.adsabs.harvard.edu/pdf/1996ApJ...457..355G|url-status=live|archiveurl=https://web.archive.org/web/20211117095828/https://articles.adsabs.harvard.edu/pdf/1996ApJ...457..355G|archivedate=2021-11-17}}</ref>

It is believed that these disks consist of a turbulent envelope of plasma, also called the active zone, that encases an extensive region of quiescent gas called the dead zone.<ref name="Layered Accretion In T Tauri Disks"/> The dead zone located at the mid-plane can slow down the flow of matter through the disk which prohibits achieving a steady state.
{{Multiple image|direction=horizontal|align=center|width=300|image1=15-044a-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg|image2=15-044b-SuperNovaRemnant-PlanetFormation-SOFIA-20150319.jpg| footer_align = center |footer=[[Supernova remnant]] ejecta producing [[Nebular hypothesis|planet-forming material]].}}

==Planetary system==
[[File:Soot-line1.jpg|thumb|upright=2|An artist's illustration giving a simple overview of the main regions of a protoplanetary disk, delineated by the soot and frost line, which for example has been observed around the star [[V883 Orionis]].<ref>{{cite web|title=Stellar Outburst Brings Water Snow Line Into View|url=http://www.eso.org/public/news/eso1626/|access-date=15 July 2016}}</ref>]]

The [[solar nebula|nebular hypothesis]] of solar system formation describes how protoplanetary disks are thought to evolve into planetary systems. Electrostatic and gravitational interactions may cause the dust and ice grains in the disk to accrete into [[planetesimal]]s. This process competes against the [[stellar wind]], which drives the gas out of the system, and gravity ([[accretion disk|accretion]]) and internal stresses ([[viscosity]]), which pulls material into the central T Tauri star. Planetesimals constitute the building blocks of both terrestrial and giant planets.<ref name=lhdb2009>{{cite journal|last=Lissauer|first=J. J.|author2=Hubickyj, O. |author3=D'Angelo, G. |author4=Bodenheimer, P. |title=Models of Jupiter's growth incorporating thermal and hydrodynamic constraints| journal=Icarus|year=2009|volume=199|issue=2| pages=338–350|arxiv=0810.5186|doi=10.1016/j.icarus.2008.10.004|bibcode=2009Icar..199..338L |s2cid=18964068}}</ref><ref name=dangelo2014>{{cite journal|last=D'Angelo|first=G.|author2=Weidenschilling, S. J. |author3=Lissauer, J. J. |author4=Bodenheimer, P. |title=Growth of Jupiter: Enhancement of core accretion by a voluminous low-mass envelope|journal=Icarus|date=2014|volume=241|pages=298–312|arxiv=1405.7305|doi=10.1016/j.icarus.2014.06.029|bibcode=2014Icar..241..298D|s2cid=118572605}}</ref>

[[File:Disk comet nebula.jpg|thumb|upright=2|A model of a protoplanetary disk]]

Some of the moons of [[Jupiter]], [[Saturn]], and [[Uranus]] are believed to have formed from smaller, circumplanetary analogs of the protoplanetary disks.<ref name="arxiv0812">{{cite book |author1=Canup, Robin M. |author1-link=Robin Canup |author2=Ward, William R. |title=Origin of Europa and the Galilean Satellites |publisher=[[University of Arizona Press]] |date=2008-12-30 |arxiv=0812.4995|bibcode = 2009euro.book...59C |page=59|isbn=978-0-8165-2844-8}}</ref><ref name=dangelo_podolak_2015>{{cite journal|last=D'Angelo|first=G.|author2= Podolak, M.|title=Capture and Evolution of Planetesimals in Circumjovian Disks|journal=The Astrophysical Journal|date=2015|volume=806|issue=1|pages=29pp|doi=10.1088/0004-637X/806/2/203|arxiv = 1504.04364 |bibcode = 2015ApJ...806..203D |s2cid=119216797}}</ref>  The formation of planets and moons in geometrically thin, gas- and dust-rich disks is the reason why the [[planets]] are arranged in an [[ecliptic plane]]. Tens of millions of years after the formation of the Solar System, the inner few AU of the Solar System likely contained dozens of moon- to Mars-sized bodies that were accreting and consolidating into the terrestrial planets that we now see. The Earth's moon likely formed after a Mars-sized protoplanet obliquely [[Giant impact hypothesis|impacted]] the proto-Earth ~30 million years after the formation of the Solar System.

==Debris disks==
Gas-poor disks of circumstellar dust have been found around many nearby stars—most of which have ages in the range of ~10 million years (e.g. [[Beta Pictoris]], [[51 Ophiuchi]]) to billions of years (e.g. [[Tau Ceti]]). These systems are usually referred to as "[[debris disks]]". Given the older ages of these stars, and the short lifetimes of micrometer-sized dust grains around stars due to [[Poynting Robertson drag]], collisions, and [[radiation pressure]] (typically hundreds to thousands of years), it is thought that this dust is from the collisions of planetesimals (e.g. [[asteroids]], [[comets]]). Hence the [[debris disks]] around these examples (e.g. [[Vega]], [[Alphecca]], [[Fomalhaut]], etc.) are not "protoplanetary", but represent a later stage of disk evolution where extrasolar analogs of the [[asteroid belt]] and [[Kuiper belt]] are home to dust-generating collisions between planetesimals.

==Relation to abiogenesis==
{{main|Abiogenesis|Panspermia}}
Based on recent [[computer simulation|computer model studies]], the [[organic compound|complex organic molecules]] necessary for [[life]] may have  formed in the protoplanetary disk of [[cosmic dust|dust grains]] surrounding the [[Sun]] before the formation of the Earth.<ref name="Space-20120329">{{cite web |last=Moskowitz |first=Clara |title=Life's Building Blocks May Have Formed in Dust Around Young Sun |url=http://www.space.com/15089-life-building-blocks-young-sun-dust.html |date=29 March 2012 |publisher=[[Space.com]] |access-date=30 March 2012 }}</ref>  According to the computer studies, this same process may also occur around other [[stars]] that acquire [[planets]].<ref name="Space-20120329" /> (Also see [[Abiogenesis#Observed extraterrestrial organic molecules|Extraterrestrial organic molecules]].)

==Gallery==
<gallery>
Image:Opo0113i.jpg|Illustration of the dynamics of a [[proplyd]]
File:Pitch perfect in DSHARP at ALMA.jpg|20 protoplanetary discs captured by the [[High Angular Resolution Project]] (DSHARP).<ref>{{cite web |title=Pitch perfect in DSHARP at ALMA |url=https://www.eso.org/public/images/potw1904a/ |website=www.eso.org |access-date=28 January 2019 |language=en}}</ref> 
File:Cosmic shadow of HBC 672.jpg|A shadow is created by the protoplanetary disc surrounding the star [[HBC 672]] within the nebula.<ref>{{cite web |title=Hubble reveals cosmic Bat Shadow in the Serpent's Tail |url=https://www.spacetelescope.org/news/heic1819/ |website=www.spacetelescope.org |access-date=5 November 2018}}</ref>
File:Young planet creates a scene.jpg|Protoplanetary disc [[AS 209]] nestled in the young [[Ophiuchus (constellation)|Ophiuchus]] star-forming region.<ref>{{cite web|title=Young planet creates a scene|url=https://www.eso.org/public/images/potw1809a/|website=www.eso.org|access-date=26 February 2018}}</ref>
Image:Feeding a Baby Star with a Dusty Hamburger.jpg|Protoplanetary disk [[HH 212]].<ref>{{cite web|title=Feeding a Baby Star with a Dusty Hamburger|url=https://www.eso.org/public/images/potw1720a/|website=www.eso.org|access-date=15 May 2017}}</ref>
File:Spring Cleaning in an Infant Star System.jpg|By observing dusty protoplanetary discs, scientists investigate the first steps of planet formation.<ref>{{cite web|title=Spring Cleaning in an Infant Star System|url=https://www.eso.org/public/images/potw1714a/|website=www.eso.org|access-date=3 April 2017}}</ref>
Image:Boulevard_of_Broken_Rings.jpg|Concentric rings around young star [[HD 141569A]], located some 370 light-years away.<ref>{{cite web|title=Boulevard of Broken Rings|url=http://www.eso.org/public/images/potw1625a/|access-date=21 June 2016}}</ref>
Image:NASA-14114-HubbleSpaceTelescope-DebrisDisks-20140424.jpg|[[Debris disks]] detected in [[Hubble Space Telescope|HST]] images of young stars, ''[[HD 141943]]'' and ''[[HD 191089]]'' - images at top; geometry at bottom.<ref name="NASA-20140424">{{cite web |last1=Harrington |first1=J.D. |last2=Villard |first2=Ray |title=RELEASE 14-114 Astronomical Forensics Uncover Planetary Disks in NASA's Hubble Archive |url=http://www.nasa.gov/press/2014/april/astronomical-forensics-uncover-planetary-disks-in-nasas-hubble-archive |date=24 April 2014 |work=[[NASA]] |url-status=live |archive-date=2014-04-25 |archive-url=https://web.archive.org/web/20140425125432/http://www.nasa.gov/press/2014/april/astronomical-forensics-uncover-planetary-disks-in-nasas-hubble-archive/ |access-date=2014-04-25 }}</ref>
Image:Protoplanetary disk HH-30.jpg|Protoplanetary disk [[HH-30]] in [[Taurus (constellation)|Taurus]] - disk emits the reddish [[stellar jet]].
Image:Artist’s Impression of a Baby Star Still Surrounded by a Protoplanetary Disc.jpg|Artist's impression of a protoplanetary disk. 
Image:M42proplyds.jpg|A proplyd in the [[Orion Nebula]].
Image:Artist's impression of the disc around a young star.ogv|Video shows the evolution of the disc around a young star like [[HL Tauri]] (artist concept).
Image:GW Orionis 2.jpg|Image of the circumtrinary disc around [[GW Orionis]].<ref name="Bi2020"/>
Image:David A. Aguilar's Red Dwarf Stars.jpg|An artist's concept of a protoplanetary disk
Image:177-341W collage Aru et al 2024.png|Components of proplyd 177-341W in the [[Orion Nebula]] observed with [[Very Large Telescope|VLT]] [[Multi-unit spectroscopic explorer|MUSE]], showing an ionization front, protoplanetary disk, and tail<ref>{{cite journal |last1=Aru |first1=Mari-Liis |last2=Mauco |first2=Karina |last3=Manara |first3=Carlo F. |title=A tell-tale tracer for externally irradiated protoplanetary disks: Comparing the [C I] 8727 Å line and ALMA observations in proplyds |journal=Astronomy & Astrophysics |volume=692 |pages=A137 |date=December 2024 |doi=10.1051/0004-6361/202451737 |url=https://www.aanda.org/articles/aa/full_html/2024/12/aa51737-24/aa51737-24.html|arxiv=2410.21018 }}</ref>
</gallery>

==See also==
{{Commons|Protoplanetary disks}}
{{div col|colwidth=30em}}
* [[Accretion disk]]
* {{annotated link|Circumplanetary disk}}
* [[Debris disk]]
* [[Disk wind]] – material ejected from a disk
* [[Disrupted planet]]
* [[Exoasteroid]]
* [[Formation and evolution of the Solar System]]
* [[Herbig–Haro object]]
* [[Nebular hypothesis]]
* [[Q-PACE]] – a spacecraft mission to study accretion
* [[Planetary system]]
{{div col end}}

==References==
{{reflist|refs=

<ref name="Bi2020">{{cite journal | title=GW Ori: Interactions between a Triple-star System and Its Circumtriple Disk in Action | last1=Bi | first1=Jiaqing | last2=van der Marel | first2=Nienke | last3=Dong | first3=Ruobing | last4=Muto | first4=Takayuki | last5=Martin | first5=Rebecca G. | last6=Smallwood | first6=Jeremy L. | last7=Hashimoto | first7=Jun | last8=Liu | first8=Hauyu Baobab | last9=Nomura | first9=Hideko | last10=Hasegawa | first10=Yasuhiro | last11=Takami | first11=Michihiro | last12=Konishi | first12=Mihoko | last13=Momose | first13=Munetake | last14=Kanagawa | first14=Kazuhiro D. | last15=Kataoka | first15=Akimasa | last16=Ono | first16=Tomohiro | last17=Sitko | first17=Michael L. | last18=Takahashi | first18=Sanemichi Z. | last19=Tomida | first19=Kengo | last20=Tsukagoshi | first20=Takashi | display-authors=1 | journal=The Astrophysical Journal | volume=895 | issue=1 | at=L18 | year=2020 | arxiv=2004.03135  | bibcode=2020ApJ...895L..18B | bibcode-access=free | doi=10.3847/2041-8213/ab8eb4 | doi-access=free }}</ref>

}}<ref>{{Cite web |title=Home {{!}} Center for Astrophysics {{!}} Harvard & Smithsonian |url=https://www.cfa.harvard.edu/ |access-date=2024-08-01 |website=www.cfa.harvard.edu}}</ref>

==Further reading==
{{Refbegin}}
* {{Cite journal
 | last1 = Davis
 | first1 = Sanford S.
 | title = A New Model for Water Vapor and Ice Abundance in a Protoplanetary Nebula
 | journal = American Astronomical Society, DPS Meeting #38, #66.07
 | date = 2006
 | bibcode = 2006DPS....38.6607D
 | volume = 38
 | pages = 617
}}.
* {{cite journal
 | last=Barrado y Navascues
 | first=D.
 | date=1998
 | title=The Castor moving group: The age of Fomalhaut and Vega
 | url=http://aa.springer.de/papers/8339003/2300831/small.htm
 | journal=Astronomy and Astrophysics
 | volume=339
 | issue=3
 | pages=831–839
 | arxiv=astro-ph/9905243
 | bibcode=1998A&A...339..831B
 | access-date=2007-06-22
 | archive-url=https://web.archive.org/web/20070929095617/http://aa.springer.de/papers/8339003/2300831/small.htm
 | archive-date=2007-09-29
 | url-status=dead
 }}

* {{cite journal
 | last1=Kalas | first1=Paul  | author-link=Paul Kalas
 | first2=J. | last2=Graham
 | first3=M. | last3=Clampin
 | date=2005
 | title=A planetary system as the origin of structure in Fomalhaut's dust belt
 | journal=Nature
 | volume=435
 | issue=7045
 | pages=1067–70
 | doi=10.1038/nature03601
 | pmid=15973402
| bibcode=2005Natur.435.1067K
|arxiv = astro-ph/0506574 | s2cid=4406070 }}
{{Refend}}
* {{Cite journal | last1 = Williams | first1 = J. P. | last2 = Cieza | first2 = L. A. | doi = 10.1146/annurev-astro-081710-102548 | title = Protoplanetary Disks and Their Evolution | journal = [[Annual Review of Astronomy and Astrophysics]] | volume = 49 | pages = 67–117 | year = 2011 | issue = 1 |arxiv = 1103.0556 |bibcode = 2011ARA&A..49...67W | s2cid = 58904348 }} 
* {{Cite journal | last1 = Armitage | first1 = P. J. | doi = 10.1146/annurev-astro-081710-102521 | title = Dynamics of Protoplanetary Disks | journal = [[Annual Review of Astronomy and Astrophysics]] | volume = 49 | pages = 195–236 | year = 2011 | issue = 1 |arxiv = 1011.1496 |bibcode = 2011ARA&A..49..195A | s2cid = 55900935 }}

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