Protoplanet: Difference between revisions

{{Short description|Large planetary embryo}}

[[File:Vesta full mosaic.jpg|thumb|A surviving protoplanet, [[4 Vesta|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 [[planetesimal]]s that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant [[planet]]s.

==The planetesimal hypothesis==

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.<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>

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,<ref>{{cite web|url=https://www.universetoday.com/37053/protoplanets/|title=Protoplanets

|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==

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 10²² to 10²³&nbsp;kg and were a few thousand kilometers in diameter.{{fact|date=October 2022}}

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]].{{fact|date=October 2022}}

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

|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

|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}}

==Extrasolar protoplanets==

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, Sasch P.|display-authors=4|author2=Amara, Adam|author3=Meyer, Michael P.|author4=Kenworthy, Matthew P.|author5=Kasper, Markus|author6=Girard, Julien H.|date=2013|title=A young protoplanet candidate embedded in the circumstellar disk of HD 100546|journal= Astrophysical Journal|volume=766|issue=1|at=L1|doi=10.1088/2041-8205/766/1/l1|arxiv = 1302.7122 |bibcode = 2013ApJ...766L...1Q |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>

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>

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>

{| class="wikitable"

|+List of confirmed protoplanets (described as "protoplanets" in literature)

!Star

!Exoplanet

!Mass

({{Jupiter mass|link=true}})

!Period

(yr)

!separation

([[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

|2014<ref>{{Cite journal |last1=Reggiani |first1=Maddalena |last2=Quanz |first2=Sascha P. |last3=Meyer |first3=Michael R. |last4=Pueyo |first4=Laurent |last5=Absil |first5=Olivier |last6=Amara |first6=Adam |last7=Anglada |first7=Guillem |last8=Avenhaus |first8=Henning |last9=Girard |first9=Julien H. |last10=Carrasco Gonzalez |first10=Carlos |last11=Graham |first11=James |last12=Mawet |first12=Dimitri |last13=Meru |first13=Farzana |last14=Milli |first14=Julien |last15=Osorio |first15=Mayra |date=2014-09-01 |title=Discovery of a Companion Candidate in the HD 169142 Transition Disk and the Possibility of Multiple Planet Formation |url=https://ui.adsabs.harvard.edu/abs/2014ApJ...792L..23R |journal=The Astrophysical Journal |volume=792 |issue=1 |pages=L23 |arxiv=1408.0813 |bibcode=2014ApJ...792L..23R |doi=10.1088/2041-8205/792/1/L23 |issn=0004-637X |s2cid=37427761}}</ref>/2023<ref>{{Cite web |title=HD 169142 {{!}} NASA Exoplanet Archive |url=https://exoplanetarchive.ipac.caltech.edu/overview/HD%20169142 |access-date=2023-04-11 |website=exoplanetarchive.ipac.caltech.edu}}</ref>

|Direct imaging<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}}</ref>

|}

=== 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 |url=https://ui.adsabs.harvard.edu/abs/2020MNRAS.495..451T |journal=Monthly Notices of the Royal Astronomical Society |volume=495 |issue=1 |pages=451–459 |doi=10.1093/mnras/staa1167 |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

|-

|[[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

|-

|[[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

|-

|[[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 |url=https://ui.adsabs.harvard.edu/abs/2023MNRAS.526L..41P |journal=Monthly Notices of the Royal Astronomical Society |volume=526 |issue=1 |pages=L41–L46 |doi=10.1093/mnrasl/slad010 |arxiv=2301.08759 |bibcode=2023MNRAS.526L..41P |issn=0035-8711}}</ref>

|unconfirmed candidate

|Direct imaging + Disk Kinematics

|}

==See also==

* [[Accretion (astrophysics)]]

* [[Fusor (astronomy)]]

* [[Mesoplanet]]

* [[Planetesimal]]

== External links ==

*[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}}

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[[Category:Protoplanets| ]]