Mini-Neptunus

'n Mini-Neptunus (soms bekend as 'n gasdwerg of oorgangsplaneet) is 'n planeet met 'n kleiner massa as Neptunus, maar wat soos Neptunus lyk deurdat dit 'n dik atmosfeer van waterstof en helium het, moontlik met diep lae ys, rots of vloeibare oseane (van water, ammoniak, 'n mengsel van die twee of swaarder vlugtige stowwe).^[1]

'n Gasdwerg is 'n gasplaneet met 'n rotsagtige kern wat 'n dik bedekking van waterstof, helium en ander vlugtige stowwe versamel het, met 'n totale radius van tussen 1,7 en 3,9 aardradiusse (1,7-3,9 R_🜨). Die term word gebruik in 'n drielaag-, metaalgebaseerde klassifikasiewyse vir kortperiode-eksoplanete wat ook die rotsagtige, aardagtige planete insluit met 'n radius van kleiner as 1,7 R_🜨 of groter as 3,9 R_🜨, naamlik ys- en gasreuse.^[2]

Eienskappe

Teoretiese studies oor sulke planete is losweg gegrond op kennis van Uranus en Neptunus. Sonder 'n dik atmosfeer sou dit eerder as 'n oseaanplaneet geklassifiseer word.^[3] 'n Geraamde onderskeid tussen 'n aard- en gasplaneet is sowat 1,6-2 R_🜨.^[4]^[5] Planete met groter radiusse en massas het meestal 'n lae digtheid en 'n uitgebreide atmosfeer is nodig om terselfdertyd hulle massa en radius te verduidelik. Waarnemings toon planete van groter as sowat 1,6 aardradiusse (en 'n groter massa as sowat 6 aardmassas of 6 M_🜨) bevat aansienlike hoeveelhede vlugtige stowwe of waterstof-helium-gas, wat waarskynlik tydens vorming versamel is.^[6]^[1] Dit lyk of sulke planete uiteenlopende samestellings het wat nie goed verduidelik kan word aan die hand van 'n enkele massa-radius-verhouding soos dié van digter, rotsagtige planete nie.^[7]^[8]^[9]

Die laer limiet vir massa kan aansienlik wissel vir verskillende planete na gelang van hulle samestelling; die massa kan wissel van 1-20 M_🜨. Kleiner gasplanete en planete nader aan hulle moederster sal atmosferiese massa vinniger verloor as groter planete en planete verder weg.^[10]^[11] 'n Gasplaneet met 'n klein massa kan steeds 'n radius hê wat ooreenkom met dié van 'n gasreus as dit die regte temperatuur het.^[12]

Neptunusagtige planete word beskou as minder volop as sub-Neptunusse, al is hulle net effens groter.^[13]^[14] Dit is vermoedelik omdat die atmosfeer van planete van dié grootte tydens vorming, wanneer gas versamel word, die druk bereik wat nodig is om waterstof in die magmaoseaan te forseer en dus radiusgroei belemmer. Wanneer die magmaoseaan versadig is, kan radiusgroei voortgaan. Planete wat genoeg gas het om versadig te raak, is egter veel skaarser, want hulle het baie meer gas nodig.^[13]

Voorbeeld

Die kleinste bekendse eksoplaneet wat 'n gasdwerg kan wees, is Kepler-138d. Dit het 'n kleiner massa as die Aarde, maar sy volume is 60% groter. Dus het dit 'n digtheid (2,1(+2,2/-1,2) gram per cm³) wat dui op 'n aansienlike waterinhoud^[15] of moontlik 'n dik gasbedekking.^[16]

Sien ook

Verwysings

↑ ^1,0 ^1,1 D'Angelo, G.; Bodenheimer, P. (2016). "In Situ and Ex Situ Formation Models of Kepler 11 Planets". The Astrophysical Journal. 828 (1): id. 33. arXiv:1606.08088. Bibcode:2016ApJ...828...33D. doi:10.3847/0004-637X/828/1/33. S2CID 119203398.
↑ Three regimes of extrasolar planets inferred from host star metallicities, Buchhave et al.
↑ Optical to near-infrared transit observations of super-Earth GJ1214b: water-world or mini-Neptune?, E.J.W. de Mooij (1), M. Brogi (1), R.J. de Kok (2), J. Koppenhoefer (3,4), S.V. Nefs (1), I.A.G. Snellen (1), J. Greiner (4), J. Hanse (1), R.C. Heinsbroek (1), C.H. Lee (3), P.P. van der Werf (1),
↑ Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates, Daniel C. Fabrycky, Jack J. Lissauer, Darin Ragozzine, Jason F. Rowe, Eric Agol, Thomas Barclay, Natalie Batalha, William Borucki, David R. Ciardi, Eric B. Ford, John C. Geary, Matthew J. Holman, Jon M. Jenkins, Jie Li, Robert C. Morehead, Avi Shporer, Jeffrey C. Smith, Jason H. Steffen, Martin Still
↑ When Does an Exoplanet's Surface Become Earth-Like?, blogs.scientificamerican.com, 20 Junie 2012
↑ D'Angelo, G.; Bodenheimer, P. (2013). "Three-Dimensional Radiation-Hydrodynamics Calculations of the Envelopes of Young Planets Embedded in Protoplanetary Disks". The Astrophysical Journal. 778 (1): 77 (29 pp.). arXiv:1310.2211. Bibcode:2013ApJ...778...77D. doi:10.1088/0004-637X/778/1/77. S2CID 118522228.
↑ Benjamin J. Fulton et al. "The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
↑ Courtney D. Dressing et al. "The Mass of Kepler-93b and The Composition of Terrestrial Planets"
↑ Leslie A. Rogers "Most 1.6 Earth-Radius Planets are not Rocky"
↑ Feng Tian; Toon, Owen B.; Pavlov, Alexander A.; De Sterck, H. (10 Maart 2005). "Transonic hydrodynamic escape of hydrogen from extrasolar planetary atmospheres". The Astrophysical Journal. 621 (2): 1049–1060. Bibcode:2005ApJ...621.1049T. CiteSeerX 10.1.1.122.9085. doi:10.1086/427204.
↑ Mass-radius relationships for exoplanets, Damian C. Swift, Jon Eggert, Damien G. Hicks, Sebastien Hamel, Kyle Caspersen, Eric Schwegler, and Gilbert W. Collins
↑ Mass-Radius Relationships for Very Low Mass Gaseous Planets, Konstantin Batygin, David J. Stevenson, 18 April 2013
↑ ^13,0 ^13,1 "Why are there so many sub-Neptune exoplanets?". 17 Desember 2019.
↑ Superabundance of Exoplanet Sub-Neptunes Explained by Fugacity Crisis, Edwin S. Kite, Bruce Fegley Jr., Laura Schaefer, Eric B. Ford, 5 Desember 2019
↑ Jontof-Hutter, D; Rowe, J; et al. (18 Junie 2015). "Mass of the Mars-sized Exoplanet Kepler-138b from Transit Timing". Nature. 522 (7556): 321–323. arXiv:1506.07067. Bibcode:2015Natur.522..321J. doi:10.1038/nature14494. PMID 26085271. S2CID 205243944.
↑ Earth-mass exoplanet is no Earth twin – Gaseous planet challenges assumption that Earth-mass planets should be rocky

Nog leesstof

Six New Planets: Mini-Neptunes Found Around Sunlike Star, Victoria Jaggard, National Geographic News, 2 Februarie 2011
Barnes, Rory; Jackson, Brian; Raymond, Sean N.; West, Andrew A.; Greenberg, Richard (13 Januarie 2009). "The HD 40307 Planetary System: Super-Earths or Mini-Neptunes?". The Astrophysical Journal. 695 (2): 1006–1011. arXiv:0901.1698. Bibcode:2009ApJ...695.1006B. doi:10.1088/0004-637X/695/2/1006. S2CID 18849636.

Skakels

Super-Earths or Mini-Neptunes?

Hierdie artikel is in sy geheel of gedeeltelik uit die Engelse Wikipedia vertaal.

[dangelo_bodenheimer_2016-1] 1,0 ^1,1 D'Angelo, G.; Bodenheimer, P. (2016). "In Situ and Ex Situ Formation Models of Kepler 11 Planets". The Astrophysical Journal. 828 (1): id. 33. arXiv:1606.08088. Bibcode:2016ApJ...828...33D. doi:10.3847/0004-637X/828/1/33. S2CID 119203398.

[2] Three regimes of extrasolar planets inferred from host star metallicities, Buchhave et al.

[3] Optical to near-infrared transit observations of super-Earth GJ1214b: water-world or mini-Neptune?, E.J.W. de Mooij (1), M. Brogi (1), R.J. de Kok (2), J. Koppenhoefer (3,4), S.V. Nefs (1), I.A.G. Snellen (1), J. Greiner (4), J. Hanse (1), R.C. Heinsbroek (1), C.H. Lee (3), P.P. van der Werf (1),

[4] Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates, Daniel C. Fabrycky, Jack J. Lissauer, Darin Ragozzine, Jason F. Rowe, Eric Agol, Thomas Barclay, Natalie Batalha, William Borucki, David R. Ciardi, Eric B. Ford, John C. Geary, Matthew J. Holman, Jon M. Jenkins, Jie Li, Robert C. Morehead, Avi Shporer, Jeffrey C. Smith, Jason H. Steffen, Martin Still

[5] When Does an Exoplanet's Surface Become Earth-Like?, blogs.scientificamerican.com, 20 Junie 2012

[dangelo_bodenheimer_2013-6] D'Angelo, G.; Bodenheimer, P. (2013). "Three-Dimensional Radiation-Hydrodynamics Calculations of the Envelopes of Young Planets Embedded in Protoplanetary Disks". The Astrophysical Journal. 778 (1): 77 (29 pp.). arXiv:1310.2211. Bibcode:2013ApJ...778...77D. doi:10.1088/0004-637X/778/1/77. S2CID 118522228.

[7] Benjamin J. Fulton et al. "The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets

[8] Courtney D. Dressing et al. "The Mass of Kepler-93b and The Composition of Terrestrial Planets"

[9] Leslie A. Rogers "Most 1.6 Earth-Radius Planets are not Rocky"

[10] Feng Tian; Toon, Owen B.; Pavlov, Alexander A.; De Sterck, H. (10 Maart 2005). "Transonic hydrodynamic escape of hydrogen from extrasolar planetary atmospheres". The Astrophysical Journal. 621 (2): 1049–1060. Bibcode:2005ApJ...621.1049T. CiteSeerX 10.1.1.122.9085. doi:10.1086/427204.

[11] Mass-radius relationships for exoplanets, Damian C. Swift, Jon Eggert, Damien G. Hicks, Sebastien Hamel, Kyle Caspersen, Eric Schwegler, and Gilbert W. Collins

[12] Mass-Radius Relationships for Very Low Mass Gaseous Planets, Konstantin Batygin, David J. Stevenson, 18 April 2013

[cliff-13] 13,0 ^13,1 "Why are there so many sub-Neptune exoplanets?". 17 Desember 2019.

[14] Superabundance of Exoplanet Sub-Neptunes Explained by Fugacity Crisis, Edwin S. Kite, Bruce Fegley Jr., Laura Schaefer, Eric B. Ford, 5 Desember 2019

[Jontof-Hutter-15] Jontof-Hutter, D; Rowe, J; et al. (18 Junie 2015). "Mass of the Mars-sized Exoplanet Kepler-138b from Transit Timing". Nature. 522 (7556): 321–323. arXiv:1506.07067. Bibcode:2015Natur.522..321J. doi:10.1038/nature14494. PMID 26085271. S2CID 205243944.

[16] Earth-mass exoplanet is no Earth twin – Gaseous planet challenges assumption that Earth-mass planets should be rocky

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