Proplyd

In 1979 observations with the Lallemand electronic camera at the Pic-du-Midi Observatory showed six unresolved high-ionization sources near the Trapezium Cluster. These sources were not interpreted as proplyds, but as partly ionized globules (PIGs). The idea was that these objects are being ionized from the outside by M42.{{Cite journal|last1=Laques|first1=P.|last2=Vidal|first2=J. L.|date=March 1979|title=Detection of a new kind of condensations in the center of the Orion Nebula, by means of S 20 photocathodes associated with a Lallemand electronic camera.|journal=Astronomy & Astrophysics|language=en|volume=73|pages=97–106|bibcode=1979A&A....73...97L|issn=0004-6361}} Later observations with the Very Large Array showed solar-system-sized condensations associated with these sources. Here the idea appeared that these objects might be low-mass stars surrounded by an evaporating protostellar accretion disk.{{Cite journal|last1=Churchwell|first1=E.|last2=Felli|first2=M.|last3=Wood|first3=D. O. S.|last4=Massi|first4=M.|date=October 1987|title=Solar System--sized Condensations in the Orion Nebula|journal=Astrophysical Journal|language=en|volume=321|pages=516|doi=10.1086/165648|bibcode=1987ApJ...321..516C|issn=0004-637X|doi-access=free}}

Proplyds were clearly resolved in 1993 using images of the Hubble Space Telescope Wide Field Camera and the term "proplyd" was used.{{Cite journal|last1=O'dell|first1=C. R.|last2=Wen|first2=Zheng|last3=Hu|first3=Xihai|date=June 1993|title=Discovery of New Objects in the Orion Nebula on HST Images: Shocks, Compact Sources, and Protoplanetary Disks|journal=Astrophysical Journal|language=en|volume=410|pages=696|doi=10.1086/172786|bibcode=1993ApJ...410..696O|issn=0004-637X|doi-access=free}}

File:Opo0113i.jpg]]

File:177-341W collage Aru et al 2024.png MUSE, showing an ionization front, protoplanetary disk, and tail{{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 }}]]

In the Orion Nebula the proplyds observed are usually one of two types. Some proplyds glow around luminous stars, in cases where the disk is found close to the star, glowing from the star's luminosity. Other proplyds are found at a greater distance from the host star and instead show up as dark silhouettes due to the self-obscuration of cooler dust and gases from the disk itself. Some proplyds show signs of movement from solar irradiance shock waves pushing the proplyds. The Orion Nebula is approximately 1,500 light-years from the Sun with very active star formation. The Orion Nebula and the Sun are in the same spiral arm of the Milky Way galaxy.{{Cite web|url=https://www.spacetelescope.org/news/heic0917/|title=Born in beauty: proplyds in the Orion Nebula|website=www.spacetelescope.org}}{{Cite web|url=https://www.spacetelescope.org/images/opo9424b/|title=Proplyds|website=www.spacetelescope.org}}{{Cite APOD |date=22 December 2009 |title=Planetary Systems Now Forming in Orion |access-date=}}{{Cite APOD |date=7 December 1996 |title=Planetary Systems Now Forming in Orion |access-date=}}

A proplyd may form new planets and planetesimal systems. Current models show that the metallicity of the star and proplyd, along with the correct planetary system temperature and distance from the star, are keys to planet and planetesimal formation. To date, the Solar System, with 8 planets, 5 dwarf planets and 5 planetesimal systems, is the largest planetary system found.{{Cite web|url=http://www.windows2universe.org/our_solar_system/solar_system.html|title=The Solar System: The Sun, Planets, Dwarf Planets, Moons, Asteroids, Comets, Meteors, Solar System Formation - Windows to the Universe}}{{Cite web|url=https://www.universetoday.com/15451/the-solar-system/|title=Solar System Guide|first=Matt|last=Williams|date=September 5, 2015}}{{Cite web|url=https://www.universetoday.com/33059/inner-planets/|title=The Inner Planets of Our Solar System|first=Matt|last=Williams|date=December 3, 2014}} Most proplyds develop into a system with no planetesimal systems, or into one very large planetesimal system.{{Cite web|url=https://sites.astro.caltech.edu/~jwang/Project4.html|title=Planet-Metallicity Correlation|website=sites.astro.caltech.edu}}{{Cite journal|title=The Planet-Metallicity Correlation|first1=Debra A.|last1=Fischer|first2=Jeff|last2=Valenti|date=April 1, 2005|journal=The Astrophysical Journal|volume=622|issue=2 |pages=1102–1117|doi=10.1086/428383|bibcode=2005ApJ...622.1102F |s2cid=121872365 |doi-access=free}}{{Cite journal|title=Revealing A Universal Planet-Metallicity Correlation For Planets of Different Sizes Around Solar-Type Stars|first1=Ji|last1=Wang|first2=Debra A.|last2=Fischer|date=January 1, 2015|journal=The Astronomical Journal|volume=149|issue=1|pages=14|doi=10.1088/0004-6256/149/1/14|arxiv=1310.7830|bibcode=2015AJ....149...14W |s2cid=118415186 }}{{Cite web|url=http://www.astrobio.net/news-exclusive/when-stellar-metallicity-sparks-planet-formation/|work=Astrobiology Magazine |title=When Stellar Metallicity Sparks Planet Formation |first=Ray |last=Sanders |date=9 April 2012 |url-status=usurped |archive-url=https://web.archive.org/web/20201207080603/http://www.astrobio.net/news-exclusive/when-stellar-metallicity-sparks-planet-formation/ |archive-date=2020-12-07}}From Lithium to Uranium (IAU S228): Elemental Tracers of Early Cosmic Evolution

By International Astronomical Union. Symposium, by Vanessa Hill, Patrick Francois, Francesca Primas, page 509-511, "the G star problem"{{cite journal |last1=Kokubo |first1=E. |last2=Ida |first2=S. |title=Dynamics and accretion of planetesimals |journal=Progress of Theoretical and Experimental Physics |date=30 October 2012 |volume=2012 |issue=1 |pages=1A308–0 |doi=10.1093/ptep/pts032|doi-access=free |arxiv=1212.1558 }}

File:Devastated Stellar Neighborhood.jpg in Westerhout 5 as seen by the Spitzer Space Telescope]]

Photoevaporating proplyds in other star forming regions were found with the Hubble Space Telescope. NGC 1977 currently represents the star-forming region with the largest number of proplyds outside of the Orion Nebula, with 7 confirmed proplyds. It was also the first instance where a B-type star, 42 Orionis is responsible for the photoevaporation.{{Cite journal|last1=Kim|first1=Jinyoung Serena|last2=Clarke|first2=Cathie J.|last3=Fang|first3=Min|last4=Facchini|first4=Stefano|title=Proplyds Around a B1 Star: 42 Orionis in NGC 1977|date=July 2016|journal=The Astrophysical Journal|language=en|volume=826|issue=1|pages=L15|doi=10.3847/2041-8205/826/1/L15|arxiv=1606.08271|bibcode=2016ApJ...826L..15K|issn=2041-8205|hdl=10150/621402|s2cid=118562469|hdl-access=free |doi-access=free }} In addition, 4 clear and 4 candidate proplyds were discovered in the very young region NGC 2024, two of which have been photoevaporated by a B star.{{cite journal |last1=Haworth |first1=Thomas |last2=Jinyoung |first2=Kim |last3=Winter |first3=Andrew |last4=Hines |first4=Dean |last5=Clarke |first5=Cathie |last6=Sellek |first6=Andrew |last7=Ballabio |first7=Giulia |last8=Stapelfeldt |first8=Karl |title=Proplyds in the flame nebula NGC 2024 |journal=Monthly Notices of the Royal Astronomical Society |date=March 2021 |volume=501 |issue=3 |pages=3502–3514 |doi=10.1093/mnras/staa3918 |doi-access=free |arxiv=2012.09166 }} The NGC 2024 proplyds are significant because they imply that external photoevaporation of protoplanetary disks could compete even with very early planet formation (within the first half a million years).

Another type of photoevaporating proplyd was discovered with the Spitzer Space Telescope. These cometary tails represent dust being pulled away from the disks.{{Cite journal|last1=Balog|first1=Zoltan|last2=Rieke|first2=G. H.|last3=Su|first3=Kate Y. L.|last4=Muzerolle|first4=James|last5=Young|first5=Erick T.|date=2006-09-25|title=Spitzer MIPS 24 μm Detection of Photoevaporating Protoplanetary Disks|journal=The Astrophysical Journal Letters|language=en|volume=650|issue=1|pages=L83|doi=10.1086/508707|arxiv=astro-ph/0608630|bibcode=2006ApJ...650L..83B|issn=1538-4357|doi-access=free}} Westerhout 5 is a region with many dusty proplyds, especially around HD 17505.{{Cite journal|last1=Koenig|first1=X. P.|last2=Allen|first2=L. E.|author2-link=Lori Allen (astronomer)|last3=Kenyon|first3=S. J.|last4=Su|first4=K. Y. L.|last5=Balog|first5=Z.|date=2008-10-03|title=Dusty Cometary Globules in W5|journal=The Astrophysical Journal Letters|language=en|volume=687|issue=1|pages=L37|doi=10.1086/593058|arxiv=0809.1993|bibcode=2008ApJ...687L..37K|issn=1538-4357|doi-access=free}} These dusty proplyds are depleted of any gas in the outer regions of the disk, but the photoevaporation could leave an inner, more robust, and possibly gas-rich disk component of radius 5-10 astronomical units.{{Cite journal|last1=Balog|first1=Zoltan|last2=Rieke|first2=George H.|last3=Muzerolle|first3=James|last4=Bally|first4=John|last5=Su|first5=Kate Y. L.|last6=Misselt|first6=Karl|last7=Gáspár|first7=András|date=November 2008|title=Photoevaporation of Protoplanetary Disks|journal=The Astrophysical Journal|language=en|volume=688|issue=1|pages=408|doi=10.1086/592063|arxiv=0807.3724|bibcode=2008ApJ...688..408B|issn=0004-637X|doi-access=free}}

The proplyds in the Orion Nebula and other star-forming regions represent proto-planetary disks around low-mass stars being externally photoevaporated. These low-mass proplyds are usually found within 0.3 parsec (60,000 astronomical units) of the massive OB star and the dusty proplyds have tails with a length of 0.1 to 0.2 parsec (20,000 to 40,000 au). There is a proposed type of intermediate massive counterpart, called proplyd-like objects. Objects in NGC 3603 and later in Cygnus OB2 were proposed as intermediate massive versions of the bright proplyds found in the Orion Nebula. The proplyd-like objects in Cygnus OB2 for example are 6 to 14 parsec distant to a large collection of OB stars and have tail lengths of 0.11 to 0.55 parsec (24,000 to 113,000 au).{{Cite journal|last1=Wright|first1=Nicholas J.|last2=Drake|first2=Jeremy J.|last3=Drew|first3=Janet E.|last4=Guarcello|first4=Mario G.|last5=Gutermuth|first5=Robert A.|last6=Hora|first6=Joseph L.|last7=Kraemer|first7=Kathleen E.|title=Photoevaporating Proplyd-Like Objects in Cygnus Ob2|date=February 2012|journal=The Astrophysical Journal|language=en|volume=746|issue=2|pages=L21|doi=10.1088/2041-8205/746/2/L21|issn=2041-8205|arxiv=1201.2404|bibcode=2012ApJ...746L..21W|s2cid=16509383}}{{Cite journal|last1=Brandner|first1=Wolfgang|last2=Grebel|first2=Eva K.|last3=Chu|first3=You-Hua|last4=Dottori|first4=Horacio|last5=Brandl|first5=Bernhard|last6=Richling|first6=Sabine|last7=Yorke|first7=Harold W.|last8=Points|first8=Sean D.|last9=Zinnecker|first9=Hans|date=January 2000|title=HST/WFPC2 and VLT/ISAAC Observations of Proplyds in the Giant H II Region NGC 3603*|journal=The Astronomical Journal|language=en|volume=119|issue=1|pages=292|doi=10.1086/301192|arxiv=astro-ph/9910074|bibcode=2000AJ....119..292B|s2cid=15502401|issn=1538-3881}} The nature of proplyd-like objects as intermediate massive proplyds is partly supported by a spectrum for one object, which showed that the mass loss rate is higher than the mass accretion rate. Another object did not show any outflow, but accretion.{{Cite journal|last1=Guarcello|first1=M. G.|last2=Drake|first2=J. J.|last3=Wright|first3=N. J.|last4=García-Alvarez|first4=D.|last5=Kraemer|first5=K. E.|title=Accretion and Outflow in the Proplyd-Like Objects Near Cygnus Ob2|date=September 2014|journal=The Astrophysical Journal|language=en|volume=793|issue=1|pages=56|doi=10.1088/0004-637X/793/1/56|arxiv=1409.1017|bibcode=2014ApJ...793...56G|issn=0004-637X|doi-access=free}}

List is sorted after distance.

File:M42proplyds.jpg|View of several proplyds within the Orion Nebula taken by the Hubble Space Telescope

File:Proplyd 181-825 in the Orion Nebula (captured by the Hubble Space Telescope).jpg|Very bright proplyd 181-825 in the Orion Nebula, from Hubble Space Telescope

File:Proplyd 132-1832 in the Orion Nebula (captured by the Hubble Space Telescope).jpg|Dark proplyd 132-1832 in the Orion Nebula, from Hubble Space Telescope

File:Proplyd 170-249 in the Orion Nebula (captured by the Hubble Space Telescope).jpg|Bright proplyd 170-249 in the Orion Nebula, from Hubble Space Telescope. The upward tail is a jet of dust and gas blowing away from the excited proplyd

File:Proplyd 114-426 NIRCam.jpg|One of the largest dark proplyd in the Orion Nebula, Proplyd 114-426 imaged with JWST.

File:A stellar sprinkler (potw2316a).tiff|alt=ESO VLT MUSE image of proplyd 244-440 in the Orion Nebula. The young object is ejecting a jet (red color) and is surrounded by a blue halo of unknown origin.[27]|ESO VLT MUSE image of proplyd 244-440 in the Orion Nebula. The young object is ejecting a jet (red color) and is surrounded by a blue halo of unknown origin.{{Cite journal |last1=Kirwan |first1=A. |last2=Manara |first2=C. F. |last3=Whelan |first3=E. T. |last4=Robberto |first4=M. |last5=McLeod |first5=A. F. |last6=Facchini |first6=S. |last7=Beccari |first7=G. |last8=Miotello |first8=A. |last9=Schneider |first9=P. C. |last10=Murphy |first10=A. |last11=Vicente |first11=S. |date=2023-03-01 |title=A spectacular jet from the bright 244-440 Orion proplyd: the MUSE NFM view |journal=Astronomy and Astrophysics |volume=673 |pages=A166 |doi=10.1051/0004-6361/202245428 |arxiv=2303.13205 |bibcode=2023A&A...673A.166K |url=https://ui.adsabs.harvard.edu/abs/2023arXiv230313205K}}

File:Flame Nebula proplyds.jpg|Proplyds in the Flame Nebula

File:Brown dwarf proplyds Orion Nebula.jpg|Proplyds in the Orion Nebula that are brown dwarfs according to Luhman et al. 2024{{cite arXiv |last1 = Luhman |first1 = K. L. |first2=C |last2=Alves de Oliveira |first3=I. |last3=Baraffe |first4=G. |last4=Chabrier |first5=E. |last5=Manjavacas |first6=R. J. |last6=Parker |first7=P. |last7=Tremblin |author-link1 = Kevin Luhman |author-link3=Isabelle Baraffe |date = 13 Oct 2024 |title = JWST/NIRSpec Observations of Brown Dwarfs in the Orion Nebula Cluster |eprint = 2410.10000 |class = astro-ph}}

File:Proplyds in the Orion Nebula Cluster from Aru et al. 2024.png|ESO VLT MUSE images (insets) of twelve proplyds in the Orion Nebula, presented in Aru et al. 2024.{{cite journal |last1=Aru |first1=Mari-Liis | first2=Karina | last2=Mauco | last3=Manara |first3=Carlo F. |title=Kaleidoscope of irradiated disks: MUSE observations of proplyds in the Orion Nebula Cluster - I. Sample presentation and ionization front sizes |journal=Astronomy & Astrophysics |volume=687 |pages=A93 |date=July 2024 |doi=10.1051/0004-6361/202349004 |url=https://www.aanda.org/articles/aa/full_html/2024/07/aa49004-23/aa49004-23.html}} In each inset, a variety of emission lines are combined to highlight the morphology of the proplyd.

• Formation and evolution of the Solar System
• Grand tack hypothesis
• Late Heavy Bombardment
• Nice model
• Photoevaporation
• Planetary migration
• [https://commons.wikimedia.org/wiki/Proplyds_in_the_Orion_Nebula Wiki commons photos: Bright and dark proplyds in the Orion Nebula]

{{Cite journal| last=Ricci | first=L. |display-authors=etal | year= 2008 | title = The Hubble Space Telescope/Advanced Camera for Surveys Atlas of Protoplanetary Disks in the Great Orion Nebula | journal = Astronomical Journal | volume = 136 | issue= 5 | pages = 2136–2151 | doi=10.1088/0004-6256/136/5/2136 | bibcode = 2008AJ....136.2136R| doi-access= free }}

{{Cite press release| last1= Sharkey | first1= Colleen | last2= Ricci | first2 = Luca | title= Born in beauty: proplyds in the Orion Nebula |url=https://www.spacetelescope.org/news/heic0917/| date= Dec 14, 2009 | location= Hubble/ESA, Garching, Germany | agency=NASA/ESA| access-date = Aug 4, 2015}}

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Category:Orion (constellation)