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{{Short description|Large planetary embryo}}
[[File:Dawn-image-070911.jpg|thumb|A surviving protoplanet, [[4 Vesta]].]]
[[File:Vesta full mosaic.jpg|thumb|A surviving protoplanet, [[4 Vesta|Vesta]]]]
'''Protoplanets''' are large planetary embryos that originate within [[protoplanetary disc]]s and have undergone internal melting to produce differentiated interiors. They are believed to form out of kilometer-sized [[planetesimal]]s that attract each other gravitationally and collide. According to [[solar nebula|planet-formation theory]], protoplanets perturb each other's orbits slightly and thus collide to gradually form the dominant [[planet]]s.
A '''protoplanet''' is a large planetary embryo that originated within a [[protoplanetary disk]] and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized [[planetesimal]]s that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant [[planet]]s.


==The planetesimal hypothesis==
In the case of the [[Solar System]] it is thought that the collisions of planetesimals created a few hundred planetary embryos. Such embryos were similar to [[Ceres (dwarf planet)|Ceres]] and [[Pluto]] with masses of about 10<sup>22</sup> to 10<sup>23</sup>&nbsp;kg and were a few thousand kilometers in diameter. Over the course of hundreds of millions of years, they collided with one another. The exact sequence whereby planetary embryos collided to assemble the planets is not known, but it is thought that initial collisions would have replaced the first "generation" of embryos with a second generation consisting of fewer but larger embryos. These in their turn would have collided to create a third generation of fewer but even larger embryos. Eventually only a handful of embryos were left, which collided to complete the assembly of the [[planet]]s proper.<ref>{{cite book
A [[planetesimal]] is an object formed from dust, rock, and other materials, measuring from meters to hundreds of kilometers in size.
|title=An Introduction to the Solar System
According to the [[Chamberlin–Moulton planetesimal hypothesis]] and the theories of [[Viktor Safronov]], a protoplanetary disk of materials such as gas and dust would orbit a star early in the formation of a planetary system. The action of [[gravity]] on such materials form larger and larger chunks until some reach the size of planetesimals.<ref name="Cessna">{{cite web |last1=Cessna |first1=Abby |title=Planetesimals |url=https://www.universetoday.com/35974/planetesimals/ |website=Universe Today |access-date=5 April 2022 |date=26 July 2009}}</ref><ref name="Ahrens">{{cite journal |last1=Ahrens |first1=T J |title=Impact Erosion of Terrestrial Planetary Atmospheres |journal=Annual Review of Earth and Planetary Sciences |date=1 May 1993 |volume=21 |issue=1 |pages=525–555 |doi=10.1146/annurev.ea.21.050193.002521 |bibcode=1993AREPS..21..525A |url=https://doi.org/10.1146/annurev.ea.21.050193.002521 |access-date=5 April 2022 |issn=0084-6597|hdl=2060/19920021677 |hdl-access=free }}</ref>
|pages=56
|first=Neil
|last=McBride
|coauthors=Iain Gilmour, Philip A. Bland, Elaine A. Moore, Mike Widdowson, Ian Wright
|publisher=Cambridge University Press
|location=Cambridge
|year=2004
|isbn=978052183735{{Please check ISBN|reason=Invalid length.}}}}</ref>


It is thought that the collisions of planetesimals created a few hundred larger planetary embryos. Over the course of hundreds of millions of years, they collided with one another. The exact sequence whereby planetary embryos collided to assemble the planets is not known, but it is thought that initial collisions would have replaced the first "generation" of embryos with a second generation consisting of fewer but larger embryos. These in their turn would have collided to create a third generation of fewer but even larger embryos. Eventually, only a handful of embryos were left, which collided to complete the assembly of the [[planet]]s proper.<ref>{{cite book|title=An Introduction to the Solar System|pages=56|first=Neil|last=McBride|author2=Iain Gilmour |author3=Philip A. Bland |author4=Elaine A. Moore |author5=Mike Widdowson |author6=Ian Wright |publisher=[[Cambridge University Press]]|location=Cambridge|year=2004|isbn=9780521837354}}</ref>
Early protoplanets had more [[radioactive]] elements, the quantity of which has been reduced over time due to [[radioactive decay]]. Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier [[Chemical element|element]]s sank to the center, while lighter elements rose to the surface. Such a process is known as [[planetary differentiation]]. The composition of some [[meteorite]]s show that differentiation took place in some [[asteroid]]s.


Early protoplanets had more [[radioactive]] elements,<ref>{{cite web|url=https://www.universetoday.com/37053/protoplanets/|title=Protoplanets
The [[giant impact hypothesis]] proposes that [[Earth]]'s [[Moon]] formed from a colossal impact of a hypothetical protoplanet, named [[Theia (planet)|Theia]], with Earth, early in the [[Formation and evolution of the Solar System|Solar System's history]].
|first=Abby|last=Cessna|year=2009|publisher=Universe Today}}</ref> the quantity of which has been reduced over time due to [[radioactive decay]]. Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier [[Chemical element|element]]s sank to the center, whereas lighter elements rose to the surface. Such a process is known as [[planetary differentiation]]. The composition of some [[meteorite]]s show that differentiation took place in some [[asteroid]]s.


==Evidence in the Solar System - surviving remnant protoplanets==
In the inner Solar System, the three protoplanets to survive more-or-less intact are the [[asteroid]]s 1 Ceres, [[2 Pallas]], and [[4 Vesta]]. The asteroid [[21 Lutetia]] has also shown characteristics that resemble a protoplanet.<ref>{{cite web
In the case of the [[Solar System]], it is thought that the collisions of planetesimals created a few hundred planetary embryos. Such embryos were similar to [[Ceres (dwarf planet)|Ceres]] and [[Pluto]] with masses of about 10<sup>22</sup> to 10<sup>23</sup>&nbsp;kg and were a few thousand kilometers in diameter.{{fact|date=October 2022}}
| last =

| first =
According to the [[giant impact hypothesis]], the [[Moon]] formed from a colossal impact of a hypothetical protoplanet called [[Theia (planet)|Theia]] with Earth, early in the [[Formation and evolution of the Solar System|Solar System's history]].<ref name="Nace2016">{{cite web
| authorlink =
|last1=Nace |first1=Trevor
| coauthors =
|title = New Evidence For 4.5 Billion Year Old Impact Formed Our Moon
| title = BIG PIC: 2 Pallas, the Asteroid with Protoplanetary Attitude
| work = [[Discovery Space]]
|work = [[Forbes]]
|url = https://www.forbes.com/sites/trevornace/2016/01/30/new-evidence-4-5-billion-year-old-impact-formed-moon/
| publisher = [[Discovery Communications]]
| date = 2009-10-08
|date = 2016-01-30
|access-date = 2016-01-30
| url = http://dsc.discovery.com/space/big-pic/hubble-pallas-asteroid-protoplanet.html
}}</ref><ref>{{cite journal |last1=Young |first1=E. D. |last2=Kohl |first2=I. E. |last3=Warren |first3=P. H. |last4=Rubie |first4=D. C. |last5=Jacobson |first5=S. A. |last6=Morbidelli |first6=A. |title=Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact |journal=Science |date=28 January 2016 |volume=351 |issue=6272 |pages=493–496 |doi=10.1126/science.aad0525|pmid=26823426 |arxiv=1603.04536 |bibcode=2016Sci...351..493Y |s2cid=6548599 }}</ref><ref>{{cite web|last1=Wolpert|first1=Stuart|title=Moon was produced by a head-on collision between Earth and a forming planet|date=January 28, 2016|url=http://newsroom.ucla.edu/releases/moon-was-produced-by-a-head-on-collision-between-earth-and-a-forming-planet|website=UCLA newsroom|publisher=UCLA}}</ref>
| doi =

| accessdate = 2009-10-08}}
In the inner Solar System, the three protoplanets to survive more-or-less intact are the [[asteroid]]s [[Ceres (dwarf planet)|Ceres]], [[2 Pallas|Pallas]], and [[4 Vesta|Vesta]]. [[16 Psyche|Psyche]] is likely the survivor of a violent hit-and-run with another object that stripped off the outer, rocky layers of a protoplanet.<ref name=NASA15-196>{{cite web|url=http://www.nasa.gov/press-release/nasa-selects-investigations-for-future-key-planetary-mission|title=NASA Selects Investigations for Future Key Planetary Mission|date=30 September 2015 }}</ref> The asteroid [[9 Metis|Metis]] may also have a similar origin history to that of Psyche.<ref name="Kelley00">{{cite journal|last=Kelley |first=Michael S|author2=Michael J. Gaffey
</ref><ref>{{cite web
|title=9 Metis and 113 Amalthea: A Genetic Asteroid Pair|journal=Icarus|volume=144 |issue=1 |pages=27–38 |date=2000|doi=10.1006/icar.1999.6266 |bibcode=2000Icar..144...27K}}</ref> The asteroid [[21 Lutetia|Lutetia]] also has characteristics that resemble a protoplanet.<ref>{{cite web
| last = Klotz
|title = BIG PIC: 2 Pallas, the Asteroid with Protoplanetary Attitude|work = Discovery Space| publisher = [[Discovery Communications]]| date = 2009-10-08| url = http://dsc.discovery.com/space/big-pic/hubble-pallas-asteroid-protoplanet.html| access-date = 2009-10-08}}</ref><ref>{{cite web| last = Klotz| first = Irene| title = ASTEROID FAILS TO MAKE IT BIG: A newly studied asteroid is actually a planetary building block that stopped growing.| work = [[Discovery News]]| publisher = [[Discovery Communications]]| date = 2011-10-27|url=http://news.discovery.com/space/asteroid-protoplanet-lutetia-rosetta-111027.html| access-date = 2011-10-27}}</ref> [[Kuiper belt|Kuiper-belt]] [[dwarf planet]]s have also been referred to as protoplanets.<ref name=msnbc>{{cite web|date=2009-10-08|title=Protoplanet frozen in time|publisher=[[MSNBC]]|author=Alan Boyle|url=http://cosmiclog.msnbc.msn.com/archive/2009/10/08/2092402.aspx|archive-url=https://web.archive.org/web/20091010023833/http://cosmiclog.msnbc.msn.com/archive/2009/10/08/2092402.aspx|url-status=dead|archive-date=2009-10-10|access-date=2009-09-12}}</ref> Because [[iron meteorite]]s have been found on Earth, it is deemed likely that there once were other metal-cored protoplanets in the [[asteroid belt]] that since have been disrupted and that are the source of these meteorites.{{fact|date=October 2022}}
| first = Irene

| authorlink =
==Extrasolar protoplanets - observed protoplanets==
| coauthors =
In February 2013 astronomers made the first direct observation of a candidate protoplanet forming in a disk of gas and dust around a distant star, [[HD 100546]].<ref>{{cite web|url=http://www.eso.org/public/news/eso1310/|title=The Birth of a Giant Planet?|publisher=[[European Southern Observatory]]|date=28 February 2013|access-date=2 March 2013}}</ref><ref name="quanz13">{{cite journal |author=Quanz, Sascha P. |author2=Amara, Adam |author3=Meyer, Michael P. |author4=Kenworthy, Matthew P. |author5=Kasper, Markus |author6=Girard, Julien H. |display-authors=4 |date=2013 |title=A young protoplanet candidate embedded in the circumstellar disk of HD 100546 |journal=Astrophysical Journal |volume=766 |issue=1 |at=L1 |arxiv=1302.7122 |bibcode=2013ApJ...766L...1Q |doi=10.1088/2041-8205/766/1/l1 |s2cid=56140977}}</ref> Subsequent observations suggest that several protoplanets may be present in the gas disk.<ref>{{cite journal |last1=Garufi |first1=A. |last2=Quanz |first2=S. P. |last3=Schmid |first3=H. M. |last4=Mulders |first4=G. D. |last5=Avenhaus |first5=H. |last6=Boccaletti |first6=A. |last7=Ginski |first7=C. |last8=Langlois |first8=M. |last9=Stolker |first9=T. |last10=Augereau |first10=J.-C. |last11=Benisty |first11=M. |last12=Lopez |first12=B. |last13=Dominik |first13=C. |last14=Gratton |first14=R. |last15=Henning |first15=T. |last16=Janson |first16=M. |last17=Ménard |first17=F. |last18=Meyer |first18=M. R. |last19=Pinte |first19=C. |last20=Sissa |first20=E. |last21=Vigan |first21=A. |last22=Zurlo |first22=A. |last23=Bazzon |first23=A. |last24=Buenzli |first24=E. |last25=Bonnefoy |first25=M. |last26=Brandner |first26=W. |last27=Chauvin |first27=G. |last28=Cheetham |first28=A. |last29=Cudel |first29=M. |last30=Desidera |first30=S. |last31=Feldt |first31=M. |last32=Galicher |first32=R. |last33=Kasper |first33=M. |last34=Lagrange |first34=A.-M. |last35=Lannier |first35=J. |last36=Maire |first36=A. L. |last37=Mesa |first37=D. |last38=Mouillet |first38=D. |last39=Peretti |first39=S. |last40=Perrot |first40=C. |last41=Salter |first41=G. |last42=Wildi |first42=F. |title=The SPHERE view of the planet-forming disk around HD 100546 |journal=Astronomy & Astrophysics |date=April 2016 |volume=588 |pages=A8 |doi=10.1051/0004-6361/201527940 |url=https://www.aanda.org/articles/aa/full_html/2016/04/aa27940-15/aa27940-15.html |access-date=5 April 2022 |language=en |issn=0004-6361|doi-access=free |arxiv=1601.04983 |bibcode=2016A&A...588A...8G }}</ref>
| title = ASTEROID FAILS TO MAKE IT BIG: A newly studied asteroid is actually a planetary building block that stopped growing.

| work = [[Discovery News]]
Another protoplanet, AB Aur b, may be in the earliest observed stage of formation for a gas giant. It is located in the gas disk of the star [[AB Aurigae]]. AB Aur b is among the largest exoplanets identified, and has a distant orbit, three times as far as Neptune is from the Earth's sun. Observations of AB Aur b may challenge conventional thinking about how planets are formed. It was viewed by the [[Subaru Telescope]] and the [[Hubble Space Telescope]].<ref name="CBC">{{cite news |title=Gigantic Jupiter-like alien planet observed still 'in the womb' |url=https://www.cbc.ca/news/science/planet-in-the-womb-1.6408539 |access-date=5 April 2022 |work=CBC News |date=April 5, 2022}}</ref>
| publisher = [[Discovery Communications]]

| date = 2011-10-27
Rings, gaps, spirals, dust concentrations and shadows in [[Protoplanetary disk|protoplanetary disks]] could be caused by protoplanets. These structures are not completely understood and are therefore not seen as a proof for the presence of a protoplanet.<ref name=":3">{{Cite journal |last1=Pinte |first1=Christophe |last2=Teague |first2=Richard |last3=Flaherty |first3=Kevin |last4=Hall |first4=Cassandra |last5=Facchini |first5=Stefano |last6=Casassus |first6=Simon |date=2022-03-01 |title=Kinematic Structures in Planet-Forming Disks |journal=Protostars and Planets VII |volume=534 |page=645 |arxiv=2203.09528 |bibcode=2023ASPC..534..645P |url=https://ui.adsabs.harvard.edu/abs/2022arXiv220309528P}}</ref> One new emerging way to study the effect of protoplanets on the disk are [[Atomic and molecular astrophysics|molecular line]] observations of protoplanetary disks in the form of gas velocity maps.<ref name=":3" /> [[HD 97048|HD 97048 b]] is the first protoplanet detected by disk [[kinematics]] in the form of a kink in the gas velocity map.<ref>{{Cite journal |last1=Pinte |first1=C. |last2=van der Plas |first2=G. |last3=Ménard |first3=F. |last4=Price |first4=D. J. |last5=Christiaens |first5=V. |last6=Hill |first6=T. |last7=Mentiplay |first7=D. |last8=Ginski |first8=C. |last9=Choquet |first9=E. |last10=Boehler |first10=Y. |last11=Duchêne |first11=G. |last12=Perez |first12=S. |last13=Casassus |first13=S. |date=2019-08-01 |title=Kinematic detection of a planet carving a gap in a protoplanetary disk |url=https://ui.adsabs.harvard.edu/abs/2019NatAs...3.1109P |journal=Nature Astronomy |volume=3 |issue=12 |pages=1109–1114 |doi=10.1038/s41550-019-0852-6 |arxiv=1907.02538 |bibcode=2019NatAs...3.1109P |s2cid=195820690 |issn=2397-3366}}</ref>
| url = http://news.discovery.com/space/asteroid-protoplanet-lutetia-rosetta-111027.html
{| class="wikitable"
| doi =
|+List of confirmed protoplanets (described as "protoplanets" in literature)
| accessdate = 2011-10-27}}
!Star
</ref> [[Kuiper belt|Kuiper-belt]] [[dwarf planet]]s have also been referred to as protoplanets.<ref name=msnbc>{{cite web
!Exoplanet
|date=2009-10-08
!Mass
|title=Protoplanet frozen in time
({{Jupiter mass|link=true}})
|publisher=MSNBC
!Period
|author=Alan Boyle
(yr)
|url=http://cosmiclog.msnbc.msn.com/archive/2009/10/08/2092402.aspx
!separation
|accessdate=2009-09-12}}</ref> Because [[iron meteorite]]s have been found on Earth, it is deemed likely that there once were other metal-cored protoplanets in the [[asteroid belt]] that since have been disrupted and that are the source of these meteorites.
([[Astronomical unit|AU]])
!Distance to earth
([[parsec]])
!Year of Discovery
!Detection technique
|-
| rowspan="2" |[[PDS 70]]
|PDS 70 b
|3±1
|119
|20±2
|112<ref name=":1">{{Cite journal |last=Gaia Collaboration |date=2020-11-01 |title=VizieR Online Data Catalog: Gaia EDR3 (Gaia Collaboration, 2020) |url=https://ui.adsabs.harvard.edu/abs/2020yCat.1350....0G |journal=VizieR Online Data Catalog |pages=I/350 |doi=10.26093/cds/vizier.1350 |bibcode=2020yCat.1350....0G}}</ref>
|2018<ref name=":2">{{Cite web |title=PDS 70 {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/PDS%2070%20b#planet_PDS-70-b_collapsible |access-date=2023-03-01 |website=exoplanetarchive.ipac.caltech.edu}}</ref>
|Direct Imaging
|-
|PDS 70 c
|8±4
|227<ref name=":0">{{Cite web |title=Orbital Period Calculator {{!}} Binary System |url=https://www.omnicalculator.com/physics/orbital-period |access-date=2023-03-01 |website=www.omnicalculator.com |language=en}}</ref>
|{{Val|34|6|3}}
|112
|2019<ref name=":2" />
|Direct Imaging
|-
|[[HD 97048]]
|HD 97048 b
|2.5±0.5
|956<ref name=":0" />
|130
|184<ref name=":1" />
|2019<ref>{{Cite web |title=HD 97048 {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/HD%2097048%20b#planet_HD-97048-b_collapsible |access-date=2023-03-01 |website=exoplanetarchive.ipac.caltech.edu}}</ref>
|Disk Kinematics
|-
|[[HD 169142]]
|HD 169142 b
|3±2
|167<ref name=":0" />
|37.2±1.5
|114
|2019<ref>{{Cite journal |last=Gratton |first=R. |last2=Ligi |first2=R. |last3=Sissa |first3=E. |last4=Desidera |first4=S. |last5=Mesa |first5=D. |last6=Bonnefoy |first6=M. |last7=Chauvin |first7=G. |last8=Cheetham |first8=A. |last9=Feldt |first9=M. |last10=Lagrange |first10=A. M. |last11=Langlois |first11=M. |last12=Meyer |first12=M. |last13=Vigan |first13=A. |last14=Boccaletti |first14=A. |last15=Janson |first15=M. |date=March 2019 |title=Blobs, spiral arms, and a possible planet around HD 169142 |url=https://www.aanda.org/10.1051/0004-6361/201834760 |journal=Astronomy & Astrophysics |volume=623 |pages=A140 |arxiv=1901.06555 |bibcode=2019A&A...623A.140G |doi=10.1051/0004-6361/201834760 |issn=0004-6361}}</ref>/2023<ref name=":5">{{Cite journal |last1=Hammond |first1=Iain |last2=Christiaens |first2=Valentin |last3=Price |first3=Daniel J. |last4=Toci |first4=Claudia |last5=Pinte |first5=Christophe |last6=Juillard |first6=Sandrine |last7=Garg |first7=Himanshi |date=2023-02-01 |title=Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 b |url=https://ui.adsabs.harvard.edu/abs/2023arXiv230211302H |journal=Monthly Notices of the Royal Astronomical Society |volume=522 |issue=1 |pages=L51–L55 |arxiv=2302.11302 |bibcode=2023MNRAS.522L..51H |doi=10.1093/mnrasl/slad027 |doi-access=free}}</ref>
|Direct imaging
|}

=== Unconfirmed protoplanets ===
The confident detection of protoplanets is difficult. Protoplanets usually exist in gas-rich protoplanetary disks. Such disks can produce over-densities by a process called disk fragmentation. Such fragments can be small enough to be unresolved and mimic the appearance of a protoplanet.<ref>{{Cite journal |last1=Teague |first1=Richard |last2=Jankovic |first2=Marija R. |last3=Haworth |first3=Thomas J. |last4=Qi |first4=Chunhua |last5=Ilee |first5=John D. |date=2020-06-01 |title=A three-dimensional view of Gomez's hamburger |journal=Monthly Notices of the Royal Astronomical Society |volume=495 |issue=1 |pages=451–459 |doi=10.1093/mnras/staa1167 |doi-access=free |arxiv=2003.02061 |bibcode=2020MNRAS.495..451T |issn=0035-8711}}</ref> A number of unconfirmed protoplanet candidates are known and some detections were later questioned.
{| class="wikitable"
|+List of unconfirmed/disputed/refuted protoplanets
!Star
!Exoplanet
!Mass
({{Jupiter mass|link=true}})
!Period
(yr)
!separation
([[Astronomical unit|AU]])
!Distance to earth
([[parsec]])
!Year of Discovery
!disputed/
unconfirmed/
refuted
!Detection technique
|-
| rowspan="3" |[[LkCa 15]]
|LkCa 15 b
|
|
|12.7
|
|2012<ref>{{Cite journal |last1=Kraus |first1=Adam L. |last2=Ireland |first2=Michael J. |date=2012-01-01 |title=LkCa 15: A Young Exoplanet Caught at Formation? |url=https://ui.adsabs.harvard.edu/abs/2012ApJ...745....5K |journal=The Astrophysical Journal |volume=745 |issue=1 |pages=5 |doi=10.1088/0004-637X/745/1/5 |arxiv=1110.3808 |bibcode=2012ApJ...745....5K |issn=0004-637X}}</ref>
| rowspan="3" |refuted in 2019<ref>{{Cite journal |last1=Currie |first1=Thayne |last2=Marois |first2=Christian |last3=Cieza |first3=Lucas |last4=Mulders |first4=Gijs D. |last5=Lawson |first5=Kellen |last6=Caceres |first6=Claudio |last7=Rodriguez-Ruiz |first7=Dary |last8=Wisniewski |first8=John |last9=Guyon |first9=Olivier |last10=Brandt |first10=Timothy D. |last11=Kasdin |first11=N. Jeremy |last12=Groff |first12=Tyler D. |last13=Lozi |first13=Julien |last14=Chilcote |first14=Jeffrey |last15=Hodapp |first15=Klaus |date=2019-05-01 |title=No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals |journal=The Astrophysical Journal |volume=877 |issue=1 |pages=L3 |doi=10.3847/2041-8213/ab1b42 |doi-access=free |arxiv=1905.04322 |bibcode=2019ApJ...877L...3C |issn=0004-637X}}</ref>
|Direct imaging
|-
|LkCa 15 c
|
|
|18.6
|
|2015<ref name=":6">{{Cite journal |last1=Sallum |first1=S. |last2=Follette |first2=K. B. |last3=Eisner |first3=J. A. |last4=Close |first4=L. M. |last5=Hinz |first5=P. |last6=Kratter |first6=K. |last7=Males |first7=J. |last8=Skemer |first8=A. |last9=Macintosh |first9=B. |last10=Tuthill |first10=P. |last11=Bailey |first11=V. |last12=Defrère |first12=D. |last13=Morzinski |first13=K. |last14=Rodigas |first14=T. |last15=Spalding |first15=E. |date=2015-11-01 |title=Accreting protoplanets in the LkCa 15 transition disk |url=https://ui.adsabs.harvard.edu/abs/2015Natur.527..342S |journal=Nature |volume=527 |issue=7578 |pages=342–344 |doi=10.1038/nature15761 |pmid=26581290 |arxiv=1511.07456 |bibcode=2015Natur.527..342S |s2cid=916170 |issn=0028-0836}}</ref>
|Direct imaging
|-
|LkCa 15 d
|
|
|24.7
|
|2015<ref name=":6" />
|Direct imaging
|-
|[[HD 100546]]
|HD 100546 b
|4-13<ref>{{Cite journal |last1=Quanz |first1=Sascha P. |last2=Amara |first2=Adam |last3=Meyer |first3=Michael R. |last4=Girard |first4=Julien H. |last5=Kenworthy |first5=Matthew A. |last6=Kasper |first6=Markus |date=2015-07-01 |title=Confirmation and Characterization of the Protoplanet HD 100546 b—Direct Evidence for Gas Giant Planet Formation at 50 AU |url=https://ui.adsabs.harvard.edu/abs/2015ApJ...807...64Q |journal=The Astrophysical Journal |volume=807 |issue=1 |pages=64 |arxiv=1412.5173 |bibcode=2015ApJ...807...64Q |doi=10.1088/0004-637X/807/1/64 |hdl=1887/48578 |issn=0004-637X |s2cid=119119314}}</ref>
|249<ref name=":0" />
|53±2
|108<ref name=":1" />
|2015<ref>{{Cite web |title=HD 100546 {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/HD%20100546%20b#planet_HD-100546-b_collapsible |access-date=2023-03-01 |website=exoplanetarchive.ipac.caltech.edu}}</ref>
|disputed in 2017<ref>{{Cite journal |last1=Rameau |first1=Julien |last2=Follette |first2=Katherine B. |last3=Pueyo |first3=Laurent |last4=Marois |first4=Christian |last5=Macintosh |first5=Bruce |last6=Millar-Blanchaer |first6=Maxwell |last7=Wang |first7=Jason J. |last8=Vega |first8=David |last9=Doyon |first9=René |last10=Lafrenière |first10=David |last11=Nielsen |first11=Eric L. |last12=Bailey |first12=Vanessa |last13=Chilcote |first13=Jeffrey K. |last14=Close |first14=Laird M. |last15=Esposito |first15=Thomas M. |date=2017-06-01 |title=An Optical/Near-infrared Investigation of HD 100546 b with the Gemini Planet Imager and MagAO |journal=The Astronomical Journal |volume=153 |issue=6 |pages=244 |arxiv=1704.06317 |bibcode=2017AJ....153..244R |doi=10.3847/1538-3881/aa6cae |issn=0004-6256 |s2cid=19100982 |doi-access=free}}</ref>
|Direct imaging
|-
|[[Gomez's Hamburger]]
|GoHam b
|0.8-11.4
|
|350±50
|250
|2015<ref>{{Cite journal |last1=Berné |first1=O. |last2=Fuente |first2=A. |last3=Pantin |first3=E. |last4=Bujarrabal |first4=V. |last5=Baruteau |first5=C. |last6=Pilleri |first6=P. |last7=Habart |first7=E. |last8=Ménard |first8=F. |last9=Cernicharo |first9=J. |last10=Tielens |first10=A. G. G. M. |last11=Joblin |first11=C. |date=2015-06-01 |title=Very Large Telescope observations of Gomez's Hamburger: Insights into a young protoplanet candidate |url=https://ui.adsabs.harvard.edu/abs/2015A&A...578L...8B |journal=Astronomy and Astrophysics |volume=578 |pages=L8 |doi=10.1051/0004-6361/201526041 |arxiv=1504.02735 |bibcode=2015A&A...578L...8B |issn=0004-6361}}</ref>
|unconfirmed candidate
|Direct imaging
|-
|[[AB Aurigae]]
|[[AB Aurigae b|AB Aur b]]
|9
|
|94±49
|156<ref name=":1" />
|2022<ref>{{Cite web |title=AB Aur {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/AB%20Aur%20b#planet_AB-Aur-b_collapsible |access-date=2023-03-01 |website=exoplanetarchive.ipac.caltech.edu}}</ref>
|disputed in 2023<ref>{{Cite journal |last1=Zhou |first1=Yifan |last2=Bowler |first2=Brendan P. |last3=Yang |first3=Haifeng |last4=Sanghi |first4=Aniket |last5=Herczeg |first5=Gregory J. |last6=Kraus |first6=Adam L. |last7=Bae |first7=Jaehan |last8=Long |first8=Feng |last9=Follette |first9=Katherine B. |last10=Ward-Duong |first10=Kimberley |last11=Zhu |first11=Zhaohuan |last12=Biddle |first12=Lauren I. |last13=Close |first13=Laird M. |last14=Yushu Jiang |first14=Lillian |last15=Wu |first15=Ya-Lin |date=30 Aug 2023 |title=UV-Optical Emission of AB Aur b is Consistent with Scattered Stellar Light |journal=Astrophysical Journal |volume=166 |issue=6 |pages=11 |arxiv=2308.16223 |bibcode=2023AJ....166..220Z |doi=10.3847/1538-3881/acf9ec |doi-access=free}}</ref> and 2024<ref>{{Cite journal |last1=Biddle |first1=Lauren I. |last2=Bowler |first2=Brendan P. |last3=Zhou |first3=Yifan |last4=Franson |first4=Kyle |last5=Zhang |first5=Zhoujian |date=2024-04-01 |title=Deep Paβ Imaging of the Candidate Accreting Protoplanet AB Aur b |journal=The Astronomical Journal |volume=167 |issue=4 |pages=172 |arxiv=2402.12601 |bibcode=2024AJ....167..172B |doi=10.3847/1538-3881/ad2a52 |doi-access=free |issn=0004-6256}}</ref>
|Direct imaging
|-
|[[IM Lupi]]
|
|2-3
|
|110
|
|2022<ref>{{Cite journal |last1=Verrios |first1=Harrison J. |last2=Price |first2=Daniel J. |last3=Pinte |first3=Christophe |last4=Hilder |first4=Thomas |last5=Calcino |first5=Josh |date=2022-07-01 |title=Kinematic Evidence for an Embedded Planet in the IM Lupi Disk |journal=The Astrophysical Journal |volume=934 |issue=1 |pages=L11 |arxiv=2207.02869 |bibcode=2022ApJ...934L..11V |doi=10.3847/2041-8213/ac7f44 |issn=0004-637X |doi-access=free}}</ref>
|unconfirmed candidate
|Disk Kinematics
|-
|[[HD 163296]]
|multiple?<ref>{{Cite journal |last1=Kanagawa |first1=Kazuhiro D. |last2=Ono |first2=Tomohiro |last3=Momose |first3=Munetake |date=2023-12-01 |title=Kinematic signatures of a low-mass planet with a moderately inclined orbit in a protoplanetary disk |url=https://ui.adsabs.harvard.edu/abs/2023PASJ...75.1105K |journal=Publications of the Astronomical Society of Japan |volume=75 |issue=6 |pages=1105–1123 |doi=10.1093/pasj/psad059 |arxiv=2308.12144 |bibcode=2023PASJ...75.1105K |issn=0004-6264}}</ref>
|
|
|
|
|2022<ref name=":4">{{Cite journal |last1=Calcino |first1=Josh |last2=Hilder |first2=Thomas |last3=Price |first3=Daniel J. |last4=Pinte |first4=Christophe |last5=Bollati |first5=Francesco |last6=Lodato |first6=Giuseppe |last7=Norfolk |first7=Brodie J. |date=2022-04-01 |title=Mapping the Planetary Wake in HD 163296 with Kinematics |journal=The Astrophysical Journal |volume=929 |issue=2 |pages=L25 |arxiv=2111.07416 |bibcode=2022ApJ...929L..25C |doi=10.3847/2041-8213/ac64a7 |issn=0004-637X |s2cid=244117638 |doi-access=free}}</ref>
|unconfirmed candidates
|Disk Kinematics
|-
|[[Elias 2-27|Elias 2-24]]
|
|2-5
|
|52
|
|2023<ref>{{Cite journal |last1=Pinte |first1=C. |last2=Hammond |first2=I. |last3=Price |first3=D. J. |last4=Christiaens |first4=V. |last5=Andrews |first5=S. M. |last6=Chauvin |first6=G. |last7=Pérez |first7=L. M. |last8=Jorquera |first8=S. |last9=Garg |first9=H. |last10=Norfolk |first10=B. J. |last11=Calcino |first11=J. |last12=Bonnefoy |first12=M. |date=2023-11-01 |title=Kinematic and thermal signatures of the directly imaged protoplanet candidate around Elias 2-24 |journal=Monthly Notices of the Royal Astronomical Society |volume=526 |issue=1 |pages=L41–L46 |doi=10.1093/mnrasl/slad010 |doi-access=free |arxiv=2301.08759 |bibcode=2023MNRAS.526L..41P |issn=0035-8711}}</ref>
|unconfirmed candidate
|Direct imaging + Disk Kinematics
|}


==See also==
==See also==
* [[Accretion (astrophysics)]]
{{Portal|Astronomy|Space}}
* [[Fusor (astronomy)]]
* [[Fusor (astronomy)]]
* [[Mesoplanet]]
* [[Mesoplanet]]
* [[Planetesimal]]
* [[Planetesimal]]
* [[Planetar (astronomy)]]


==References==
==References==
{{Reflist}}
{{reflist}}


== External links ==
== External links ==
*[http://tech.groups.yahoo.com/group/mpml/message/25780 Thread on the definition of a protoplanet] (Minor Planet Mailing List : Jul 15, 2011)
*[https://archive.today/20130105085824/http://tech.groups.yahoo.com/group/mpml/message/25780 Thread on the definition of a protoplanet] (Minor Planet Mailing List : July 15, 2011)


{{Exoplanet}}
{{Exoplanet}}
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}

[[Category:Protoplanets| ]]
[[Category:Types of planet]]
[[Category:Types of planet]]

Latest revision as of 14:19, 19 November 2024

A surviving protoplanet, Vesta

A protoplanet is a large planetary embryo that originated within a protoplanetary disk and has undergone internal melting to produce a differentiated interior. Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets.

The planetesimal hypothesis

[edit]

A planetesimal is an object formed from dust, rock, and other materials, measuring from meters to hundreds of kilometers in size. According to the Chamberlin–Moulton planetesimal hypothesis and the theories of Viktor Safronov, a protoplanetary disk of materials such as gas and dust would orbit a star early in the formation of a planetary system. The action of gravity on such materials form larger and larger chunks until some reach the size of planetesimals.[1][2]

It is thought that the collisions of planetesimals created a few hundred larger planetary embryos. Over the course of hundreds of millions of years, they collided with one another. The exact sequence whereby planetary embryos collided to assemble the planets is not known, but it is thought that initial collisions would have replaced the first "generation" of embryos with a second generation consisting of fewer but larger embryos. These in their turn would have collided to create a third generation of fewer but even larger embryos. Eventually, only a handful of embryos were left, which collided to complete the assembly of the planets proper.[3]

Early protoplanets had more radioactive elements,[4] the quantity of which has been reduced over time due to radioactive decay. Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier elements sank to the center, whereas lighter elements rose to the surface. Such a process is known as planetary differentiation. The composition of some meteorites show that differentiation took place in some asteroids.

Evidence in the Solar System - surviving remnant protoplanets

[edit]

In the case of the Solar System, it is thought that the collisions of planetesimals created a few hundred planetary embryos. Such embryos were similar to Ceres and Pluto with masses of about 1022 to 1023 kg and were a few thousand kilometers in diameter.[citation needed]

According to the giant impact hypothesis, the Moon formed from a colossal impact of a hypothetical protoplanet called Theia with Earth, early in the Solar System's history.[5][6][7]

In the inner Solar System, the three protoplanets to survive more-or-less intact are the asteroids Ceres, Pallas, and Vesta. Psyche is likely the survivor of a violent hit-and-run with another object that stripped off the outer, rocky layers of a protoplanet.[8] The asteroid Metis may also have a similar origin history to that of Psyche.[9] The asteroid Lutetia also has characteristics that resemble a protoplanet.[10][11] Kuiper-belt dwarf planets have also been referred to as protoplanets.[12] Because iron meteorites have been found on Earth, it is deemed likely that there once were other metal-cored protoplanets in the asteroid belt that since have been disrupted and that are the source of these meteorites.[citation needed]

Extrasolar protoplanets - observed protoplanets

[edit]

In February 2013 astronomers made the first direct observation of a candidate protoplanet forming in a disk of gas and dust around a distant star, HD 100546.[13][14] Subsequent observations suggest that several protoplanets may be present in the gas disk.[15]

Another protoplanet, AB Aur b, may be in the earliest observed stage of formation for a gas giant. It is located in the gas disk of the star AB Aurigae. AB Aur b is among the largest exoplanets identified, and has a distant orbit, three times as far as Neptune is from the Earth's sun. Observations of AB Aur b may challenge conventional thinking about how planets are formed. It was viewed by the Subaru Telescope and the Hubble Space Telescope.[16]

Rings, gaps, spirals, dust concentrations and shadows in protoplanetary disks could be caused by protoplanets. These structures are not completely understood and are therefore not seen as a proof for the presence of a protoplanet.[17] One new emerging way to study the effect of protoplanets on the disk are molecular line observations of protoplanetary disks in the form of gas velocity maps.[17] HD 97048 b is the first protoplanet detected by disk kinematics in the form of a kink in the gas velocity map.[18]

List of confirmed protoplanets (described as "protoplanets" in literature)
Star Exoplanet Mass

(MJ)

Period

(yr)

separation

(AU)

Distance to earth

(parsec)

Year of Discovery Detection technique
PDS 70 PDS 70 b 3±1 119 20±2 112[19] 2018[20] Direct Imaging
PDS 70 c 8±4 227[21] 34+6
−3 		112 2019[20] Direct Imaging
HD 97048 HD 97048 b 2.5±0.5 956[21] 130 184[19] 2019[22] Disk Kinematics
HD 169142 HD 169142 b 3±2 167[21] 37.2±1.5 114 2019[23]/2023[24] Direct imaging

Unconfirmed protoplanets

[edit]

The confident detection of protoplanets is difficult. Protoplanets usually exist in gas-rich protoplanetary disks. Such disks can produce over-densities by a process called disk fragmentation. Such fragments can be small enough to be unresolved and mimic the appearance of a protoplanet.[25] A number of unconfirmed protoplanet candidates are known and some detections were later questioned.

List of unconfirmed/disputed/refuted protoplanets
Star Exoplanet Mass

(MJ)

Period

(yr)

separation

(AU)

Distance to earth

(parsec)

Year of Discovery disputed/

unconfirmed/ refuted

Detection technique
LkCa 15 LkCa 15 b 12.7 2012[26] refuted in 2019[27] Direct imaging
LkCa 15 c 18.6 2015[28] Direct imaging
LkCa 15 d 24.7 2015[28] Direct imaging
HD 100546 HD 100546 b 4-13[29] 249[21] 53±2 108[19] 2015[30] disputed in 2017[31] Direct imaging
Gomez's Hamburger GoHam b 0.8-11.4 350±50 250 2015[32] unconfirmed candidate Direct imaging
AB Aurigae AB Aur b 9 94±49 156[19] 2022[33] disputed in 2023[34] and 2024[35] Direct imaging
IM Lupi 2-3 110 2022[36] unconfirmed candidate Disk Kinematics
HD 163296 multiple?[37] 2022[38] unconfirmed candidates Disk Kinematics
Elias 2-24 2-5 52 2023[39] unconfirmed candidate Direct imaging + Disk Kinematics

See also

[edit]

References

[edit]
  1. ^ Cessna, Abby (26 July 2009). "Planetesimals". Universe Today. Retrieved 5 April 2022.
  2. ^ Ahrens, T J (1 May 1993). "Impact Erosion of Terrestrial Planetary Atmospheres". Annual Review of Earth and Planetary Sciences. 21 (1): 525–555. Bibcode:1993AREPS..21..525A. doi:10.1146/annurev.ea.21.050193.002521. hdl:2060/19920021677. ISSN 0084-6597. Retrieved 5 April 2022.
  3. ^ McBride, Neil; Iain Gilmour; Philip A. Bland; Elaine A. Moore; Mike Widdowson; Ian Wright (2004). An Introduction to the Solar System. Cambridge: Cambridge University Press. p. 56. ISBN 9780521837354.
  4. ^ Cessna, Abby (2009). "Protoplanets". Universe Today.
  5. ^ Nace, Trevor (2016-01-30). "New Evidence For 4.5 Billion Year Old Impact Formed Our Moon". Forbes. Retrieved 2016-01-30.
  6. ^ Young, E. D.; Kohl, I. E.; Warren, P. H.; Rubie, D. C.; Jacobson, S. A.; Morbidelli, A. (28 January 2016). "Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact". Science. 351 (6272): 493–496. arXiv:1603.04536. Bibcode:2016Sci...351..493Y. doi:10.1126/science.aad0525. PMID 26823426. S2CID 6548599.
  7. ^ Wolpert, Stuart (January 28, 2016). "Moon was produced by a head-on collision between Earth and a forming planet". UCLA newsroom. UCLA.
  8. ^ "NASA Selects Investigations for Future Key Planetary Mission". 30 September 2015.
  9. ^ Kelley, Michael S; Michael J. Gaffey (2000). "9 Metis and 113 Amalthea: A Genetic Asteroid Pair". Icarus. 144 (1): 27–38. Bibcode:2000Icar..144...27K. doi:10.1006/icar.1999.6266.
  10. ^ "BIG PIC: 2 Pallas, the Asteroid with Protoplanetary Attitude". Discovery Space. Discovery Communications. 2009-10-08. Retrieved 2009-10-08.
  11. ^ Klotz, Irene (2011-10-27). "ASTEROID FAILS TO MAKE IT BIG: A newly studied asteroid is actually a planetary building block that stopped growing". Discovery News. Discovery Communications. Retrieved 2011-10-27.
  12. ^ Alan Boyle (2009-10-08). "Protoplanet frozen in time". MSNBC. Archived from the original on 2009-10-10. Retrieved 2009-09-12.
  13. ^ "The Birth of a Giant Planet?". European Southern Observatory. 28 February 2013. Retrieved 2 March 2013.
  14. ^ Quanz, Sascha P.; Amara, Adam; Meyer, Michael P.; Kenworthy, Matthew P.; et al. (2013). "A young protoplanet candidate embedded in the circumstellar disk of HD 100546". Astrophysical Journal. 766 (1). L1. arXiv:1302.7122. Bibcode:2013ApJ...766L...1Q. doi:10.1088/2041-8205/766/1/l1. S2CID 56140977.
  15. ^ Garufi, A.; Quanz, S. P.; Schmid, H. M.; Mulders, G. D.; Avenhaus, H.; Boccaletti, A.; Ginski, C.; Langlois, M.; Stolker, T.; Augereau, J.-C.; Benisty, M.; Lopez, B.; Dominik, C.; Gratton, R.; Henning, T.; Janson, M.; Ménard, F.; Meyer, M. R.; Pinte, C.; Sissa, E.; Vigan, A.; Zurlo, A.; Bazzon, A.; Buenzli, E.; Bonnefoy, M.; Brandner, W.; Chauvin, G.; Cheetham, A.; Cudel, M.; Desidera, S.; Feldt, M.; Galicher, R.; Kasper, M.; Lagrange, A.-M.; Lannier, J.; Maire, A. L.; Mesa, D.; Mouillet, D.; Peretti, S.; Perrot, C.; Salter, G.; Wildi, F. (April 2016). "The SPHERE view of the planet-forming disk around HD 100546". Astronomy & Astrophysics. 588: A8. arXiv:1601.04983. Bibcode:2016A&A...588A...8G. doi:10.1051/0004-6361/201527940. ISSN 0004-6361. Retrieved 5 April 2022.
  16. ^ "Gigantic Jupiter-like alien planet observed still 'in the womb'". CBC News. April 5, 2022. Retrieved 5 April 2022.
  17. ^ a b Pinte, Christophe; Teague, Richard; Flaherty, Kevin; Hall, Cassandra; Facchini, Stefano; Casassus, Simon (2022-03-01). "Kinematic Structures in Planet-Forming Disks". Protostars and Planets VII. 534: 645. arXiv:2203.09528. Bibcode:2023ASPC..534..645P.
  18. ^ Pinte, C.; van der Plas, G.; Ménard, F.; Price, D. J.; Christiaens, V.; Hill, T.; Mentiplay, D.; Ginski, C.; Choquet, E.; Boehler, Y.; Duchêne, G.; Perez, S.; Casassus, S. (2019-08-01). "Kinematic detection of a planet carving a gap in a protoplanetary disk". Nature Astronomy. 3 (12): 1109–1114. arXiv:1907.02538. Bibcode:2019NatAs...3.1109P. doi:10.1038/s41550-019-0852-6. ISSN 2397-3366. S2CID 195820690.
  19. ^ a b c d Gaia Collaboration (2020-11-01). "VizieR Online Data Catalog: Gaia EDR3 (Gaia Collaboration, 2020)". VizieR Online Data Catalog: I/350. Bibcode:2020yCat.1350....0G. doi:10.26093/cds/vizier.1350.
  20. ^ a b "PDS 70 | NASA Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved 2023-03-01.
  21. ^ a b c d "Orbital Period Calculator | Binary System". www.omnicalculator.com. Retrieved 2023-03-01.
  22. ^ "HD 97048 | NASA Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved 2023-03-01.
  23. ^ Gratton, R.; Ligi, R.; Sissa, E.; Desidera, S.; Mesa, D.; Bonnefoy, M.; Chauvin, G.; Cheetham, A.; Feldt, M.; Lagrange, A. M.; Langlois, M.; Meyer, M.; Vigan, A.; Boccaletti, A.; Janson, M. (March 2019). "Blobs, spiral arms, and a possible planet around HD 169142". Astronomy & Astrophysics. 623: A140. arXiv:1901.06555. Bibcode:2019A&A...623A.140G. doi:10.1051/0004-6361/201834760. ISSN 0004-6361.
  24. ^ Hammond, Iain; Christiaens, Valentin; Price, Daniel J.; Toci, Claudia; Pinte, Christophe; Juillard, Sandrine; Garg, Himanshi (2023-02-01). "Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 b". Monthly Notices of the Royal Astronomical Society. 522 (1): L51–L55. arXiv:2302.11302. Bibcode:2023MNRAS.522L..51H. doi:10.1093/mnrasl/slad027.
  25. ^ Teague, Richard; Jankovic, Marija R.; Haworth, Thomas J.; Qi, Chunhua; Ilee, John D. (2020-06-01). "A three-dimensional view of Gomez's hamburger". Monthly Notices of the Royal Astronomical Society. 495 (1): 451–459. arXiv:2003.02061. Bibcode:2020MNRAS.495..451T. doi:10.1093/mnras/staa1167. ISSN 0035-8711.
  26. ^ Kraus, Adam L.; Ireland, Michael J. (2012-01-01). "LkCa 15: A Young Exoplanet Caught at Formation?". The Astrophysical Journal. 745 (1): 5. arXiv:1110.3808. Bibcode:2012ApJ...745....5K. doi:10.1088/0004-637X/745/1/5. ISSN 0004-637X.
  27. ^ Currie, Thayne; Marois, Christian; Cieza, Lucas; Mulders, Gijs D.; Lawson, Kellen; Caceres, Claudio; Rodriguez-Ruiz, Dary; Wisniewski, John; Guyon, Olivier; Brandt, Timothy D.; Kasdin, N. Jeremy; Groff, Tyler D.; Lozi, Julien; Chilcote, Jeffrey; Hodapp, Klaus (2019-05-01). "No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals". The Astrophysical Journal. 877 (1): L3. arXiv:1905.04322. Bibcode:2019ApJ...877L...3C. doi:10.3847/2041-8213/ab1b42. ISSN 0004-637X.
  28. ^ a b Sallum, S.; Follette, K. B.; Eisner, J. A.; Close, L. M.; Hinz, P.; Kratter, K.; Males, J.; Skemer, A.; Macintosh, B.; Tuthill, P.; Bailey, V.; Defrère, D.; Morzinski, K.; Rodigas, T.; Spalding, E. (2015-11-01). "Accreting protoplanets in the LkCa 15 transition disk". Nature. 527 (7578): 342–344. arXiv:1511.07456. Bibcode:2015Natur.527..342S. doi:10.1038/nature15761. ISSN 0028-0836. PMID 26581290. S2CID 916170.
  29. ^ Quanz, Sascha P.; Amara, Adam; Meyer, Michael R.; Girard, Julien H.; Kenworthy, Matthew A.; Kasper, Markus (2015-07-01). "Confirmation and Characterization of the Protoplanet HD 100546 b—Direct Evidence for Gas Giant Planet Formation at 50 AU". The Astrophysical Journal. 807 (1): 64. arXiv:1412.5173. Bibcode:2015ApJ...807...64Q. doi:10.1088/0004-637X/807/1/64. hdl:1887/48578. ISSN 0004-637X. S2CID 119119314.
  30. ^ "HD 100546 | NASA Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved 2023-03-01.
  31. ^ Rameau, Julien; Follette, Katherine B.; Pueyo, Laurent; Marois, Christian; Macintosh, Bruce; Millar-Blanchaer, Maxwell; Wang, Jason J.; Vega, David; Doyon, René; Lafrenière, David; Nielsen, Eric L.; Bailey, Vanessa; Chilcote, Jeffrey K.; Close, Laird M.; Esposito, Thomas M. (2017-06-01). "An Optical/Near-infrared Investigation of HD 100546 b with the Gemini Planet Imager and MagAO". The Astronomical Journal. 153 (6): 244. arXiv:1704.06317. Bibcode:2017AJ....153..244R. doi:10.3847/1538-3881/aa6cae. ISSN 0004-6256. S2CID 19100982.
  32. ^ Berné, O.; Fuente, A.; Pantin, E.; Bujarrabal, V.; Baruteau, C.; Pilleri, P.; Habart, E.; Ménard, F.; Cernicharo, J.; Tielens, A. G. G. M.; Joblin, C. (2015-06-01). "Very Large Telescope observations of Gomez's Hamburger: Insights into a young protoplanet candidate". Astronomy and Astrophysics. 578: L8. arXiv:1504.02735. Bibcode:2015A&A...578L...8B. doi:10.1051/0004-6361/201526041. ISSN 0004-6361.
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  34. ^ Zhou, Yifan; Bowler, Brendan P.; Yang, Haifeng; Sanghi, Aniket; Herczeg, Gregory J.; Kraus, Adam L.; Bae, Jaehan; Long, Feng; Follette, Katherine B.; Ward-Duong, Kimberley; Zhu, Zhaohuan; Biddle, Lauren I.; Close, Laird M.; Yushu Jiang, Lillian; Wu, Ya-Lin (30 Aug 2023). "UV-Optical Emission of AB Aur b is Consistent with Scattered Stellar Light". Astrophysical Journal. 166 (6): 11. arXiv:2308.16223. Bibcode:2023AJ....166..220Z. doi:10.3847/1538-3881/acf9ec.
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