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词条 Rogue planet
释义

  1. Observation

  2. Retention of heat in interstellar space

  3. Known or possible rogue planets

  4. See also

  5. References

  6. Bibliography

  7. External links

{{short description|A planetary-mass object that orbits the galaxy directly}}{{About|a type of astronomical object}}{{Use dmy dates|date=July 2011}}

A rogue planet (also termed an interstellar planet, nomad planet, free-floating planet, unbound planet, orphan planet, wandering planet, starless planet, or sunless planet) is a planetary-mass object that orbits a galactic center directly. Such objects have been ejected from the planetary system in which they formed or have never been gravitationally bound to any star or brown dwarf.[1][2][3] The Milky Way alone may have billions of rogue planets.[4]

Some planetary-mass objects may have formed in a similar way to stars, and the International Astronomical Union has proposed that such objects be called sub-brown dwarfs.[5] A possible example is Cha 110913-773444, which might have been ejected and become a rogue planet, or otherwise formed on its own to become a sub-brown dwarf.[6]

Astronomers have used the Herschel Space Observatory and the Very Large Telescope to observe a very young free-floating planetary-mass object, OTS 44, and demonstrate that the processes characterizing the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. Herschel far-infrared observations have shown that OTS 44 is surrounded by a disk of at least 10 Earth masses and thus could eventually form a mini planetary system.[7] Spectroscopic observations of OTS 44 with the SINFONI spectrograph at the Very Large Telescope have revealed that the disk is actively accreting matter, in a similar way to young stars.[7] In December 2013, a candidate exomoon of a rogue planet was announced.[8]

Observation

Astrophysicist Takahiro Sumi of Osaka University in Japan and colleagues, who form the Microlensing Observations in Astrophysics and the Optical Gravitational Lensing Experiment collaborations, published their study of microlensing in 2011. They observed 50 million stars in the Milky Way using the 1.8-meter MOA-II telescope at New Zealand's Mount John Observatory and the 1.3-meter University of Warsaw telescope at Chile's Las Campanas Observatory. They found 474 incidents of microlensing, ten of which were brief enough to be planets of around Jupiter's size with no associated star in the immediate vicinity. The researchers estimated from their observations that there are nearly two Jupiter-mass rogue planets for every star in the Milky Way.[9][10][11] Other estimates suggest a much larger number, up to 100,000 times more rogue planets than stars in the Milky Way.[12] A 2017 study by Przemek Mróz of Warsaw University Observatory and colleagues, with six times larger statistics than the 2011 study, indicates an upper limit on Jupiter-mass free-floating or wide-orbit planets of 0.25 planets per main-sequence star in the Milky Way.[13]

Nearby rogue planet candidates include WISE 0855−0714 at a distance of {{val|7.27|0.13|u=light-years}}.[14]

Retention of heat in interstellar space

Interstellar planets generate little heat and are not heated by a star.[15] In 1998, David J. Stevenson theorized that some planet-sized objects adrift in interstellar space might sustain a thick atmosphere that would not freeze out. He proposed that these atmospheres would be preserved by the pressure-induced far-infrared radiation opacity of a thick hydrogen-containing atmosphere.[16]

During planetary-system formation, several small protoplanetary bodies may be ejected from the system.[17] An ejected body would receive less of the stellar-generated ultraviolet light that can strip away the lighter elements of its atmosphere. Even an Earth-sized body would have enough gravity to prevent the escape of the hydrogen and helium in its atmosphere.[16] In an Earth-sized object that has a kilobar atmospheric pressure of hydrogen and a convective gas adiabat, the geothermal energy from residual core radioisotope decay could maintain a surface temperature above the melting point of water,[16] allowing liquid-water oceans to exist. These planets are likely to remain geologically active for long periods. If they have geodynamo-created protective magnetospheres and sea floor volcanism, hydrothermal vents could provide energy for life.[16] These bodies would be difficult to detect because of their weak thermal microwave radiation emissions, although reflected solar radiation and far-infrared thermal emissions may be detectable from an object that is less than 1000 astronomical units from Earth.[18] Around five percent of Earth-sized ejected planets with Moon-sized natural satellites would retain their satellites after ejection. A large satellite would be a source of significant geological tidal force heating.[19]

Known or possible rogue planets

The table below lists rogue planets, confirmed or suspected, that have been discovered. It is yet unknown whether these planets were ejected from orbiting a star or else formed on their own as sub-brown dwarfs.

Exoplanetlink=y) Age (Myr) Distance (ly) Status Discovery
OTS 44 ~11.5 0.5–3 554 Likely a low-mass brown dwarf[20] 1998
S Ori 52 2–8 1–5 1,150 Age and mass uncertain; may be a foreground brown dwarf 2000[21]
Cha 110913-773444 5–15 ~2 529 Candidate 2004[22]
SIMP J013656.5+093347 11-13 ~200 20-22 Candidate 2006[23][24]
UGPS J072227.51-054031.2 5–40 13 Mass uncertain 2010
[MPK2010b] 4450 2–3 325 Candidate 2010[25]
CFBDSIR 2149-0403 4–7 110–130 117–143 Candidate 2012[26]
MOA-2011-BLG-262 ~4 May be a red dwarf 2013
PSO J318.5-22 5.5–8 21–27 80 Confirmed 2013[27]
2MASS J2208+2921 11–13 21–27 115 Candidate; radial velocity needed 2014[28]
WISE J1741-4642 4–21 23–130 Candidate 2014[29]
WISE 0855−0714 3–10 7.1 Age uncertain; may be a brown dwarf 2014[30]
2MASS J12074836–3900043 11–13 7–13 200 Candidate; distance needed 2014[31]
SIMP J2154–1055 9–11 30–50 63 Age questioned[32] 2014[33]
SDSS J111010.01+011613.1 10–12 110–130 63 Confirmed 2015[34]
2MASS J1119–1137 4–8 7–13 94 Candidate; distance needed 2016[35]
WISEA 1147 5–13 7–13 94 Candidate; distance needed 2016[36]
OGLE-2012-BLG-1323 0.007245–0.07245 Candidate; distance needed 2017[37][38][39]
OGLE-2017-BLG-0560 1.9–20 Candidate; distance needed 2017[40][41][42]

See also

  • {{annotated link|Intergalactic star}}
  • {{annotated link|Rogue comet}}
  • Rogue extragalactic planets – Rogue planets that are outside the Milky Way galaxy

References

1. ^Shostak, Seth (24 February 2005). Orphan Planets: It's a Hard Knock Life. Space.com, 24 February 2005. Retrieved on 5 February 2009 from http://www.space.com/searchforlife/seti_orphan_planets_050224.html.
2. ^Lloyd, Robin (18 April 2001). Free-Floating Planets – British Team Restakes Dubious Claim. Space.com, 18 April 2001. Retrieved on 5 February 2009 from http://www.space.com/scienceastronomy/astronomy/free_floaters_010403-1.html. {{webarchive | url=https://web.archive.org/web/20081013054054/http://www.space.com/scienceastronomy/astronomy/free_floaters_010403-1.html | date=13 October 2008}}
3. ^Author unknown (18 April 2001). Orphan 'planet' findings challenged by new model. NASA Astrobiology, 18 April 2001. Retrieved on 5 February 2009 from {{cite web | url=http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id%3D783 | title=Archived copy | accessdate=9 February 2009 | deadurl=yes | archiveurl=https://web.archive.org/web/20090322091340/http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=783 | archivedate=22 March 2009 | df=dmy-all }}.
4. ^Neil deGrasse Tyson in A Spacetime Odyssey as referred to by National Geographic
5. ^Working Group on Extrasolar Planets – Definition of a "Planet" Position Statement on the Definition of a "Planet" (IAU) {{webarchive | url=https://web.archive.org/web/20060916161707/http://www.dtm.ciw.edu/boss/definition.html | date=16 September 2006}}
6. ^Rogue planet find makes astronomers ponder theory
7. ^1 {{cite journal | last1=Joergens | first1=V. | last2=Bonnefoy | first2=M. | last3=Liu | first3=Y. | last4=Bayo | first4=A. | last5=Wolf | first5=S. | last6=Chauvin | first6=G. | last7=Rojo | first7=P. | title=OTS 44: Disk and accretion at the planetary border | journal=Astronomy & Astrophysics | volume=558 | number=7 | date=2013 | doi=10.1051/0004-6361/201322432 | arxiv=1310.1936 | bibcode=2013A&A...558L...7J | page=L7}}
8. ^{{cite journal | title=A Sub-Earth-Mass Moon Orbiting a Gas Giant Primary or a High Velocity Planetary System in the Galactic Bulge | arxiv=1312.3951 | first1=D.P. |last1=Bennett |first2=V. | last2=Batista | display-authors=etal | date=13 December 2013 | doi=10.1088/0004-637X/785/2/155 | volume=785 | issue=2 | pages=155 | journal=The Astrophysical Journal | bibcode=2014ApJ...785..155B}}
9. ^Homeless' Planets May Be Common in Our Galaxy {{webarchive | url=https://web.archive.org/web/20121008190445/http://news.sciencemag.org/sciencenow/2011/05/homeless-planets-may-be-common.html?ref=hp | date=8 October 2012}} by Jon Cartwright, Science Now, 18 May 2011, Accessed 20 May 2011
10. ^Planets that have no stars: New class of planets discovered, Physorg.com, 18 May 2011. Accessed May 2011.
11. ^{{cite journal | author=T. Sumi | arxiv=1105.3544v1 | title=Unbound or Distant Planetary Mass Population Detected by Gravitational Microlensing | date=2011 | display-authors=etal | doi=10.1038/nature10092 | pmid=21593867 | volume=473 | issue=7347 | journal=Nature | pages=349–352 | bibcode=2011Natur.473..349S}}
12. ^{{cite web | title=Researchers say galaxy may swarm with 'nomad planets' | url=http://news.stanford.edu/news/2012/february/slac-nomad-planets-022312.html | accessdate=29 February 2012 | publisher=Stanford University| date=2012-02-23 }}
13. ^{{cite journal | author=P. Mroz | arxiv=1707.07634 | title=No large population of unbound or wide-orbit Jupiter-mass planets | date=2017 | display-authors=etal | doi=10.1038/nature23276 | pmid=28738410 | volume=548 | issue=7666 | journal=Nature | pages=183–186 | bibcode=2017Natur.548..183M}}
14. ^{{cite journal |title=The Spectral Energy Distribution of the Coldest Known Brown Dwarf |journal=The Astronomical Journal |first1=Kevin L. |last1=Luhman |first2=Taran L. |last2=Esplin |volume=152 |issue=2 |at=78 |date=September 2016 |doi=10.3847/0004-6256/152/3/78 |bibcode=2016AJ....152...78L |arxiv=1605.06655}}
15. ^{{cite web | url=https://aeon.co/essays/could-we-make-our-home-on-a-rogue-planet-without-a-sun | title=Life in the dark | publisher=Aeon | language=English | author=Sean Raymond | date=9 April 2005 | accessdate=9 April 2016}}
16. ^1 2 3 {{cite journal | journal=Nature | date=1999 | title=Life-sustaining planets in interstellar space? | first=David J. | last=Stevenson | doi=10.1038/21811 | volume=400 | page=32 | last2=Stevens | first2=C. F. | issue=6739 | bibcode= 1999Natur.400...32S | pmid=10403246}}
17. ^{{cite journal | last=Lissauer | first= J. J. | title=Timescales for Planetary Accretion and the Structure of the Protoplanetary disk | journal=Icarus | volume=69 | issue=2 | pages=249–265| date=1987| doi=10.1016/0019-1035(87)90104-7 | bibcode=1987Icar...69..249L| hdl= 2060/19870013947 }}
18. ^{{cite journal | title=The Steppenwolf: A proposal for a habitable planet in interstellar space | arxiv=1102.1108 | author=Dorian S. Abbot | author2=Eric R. Switzer | date=2 June 2011 | doi=10.1088/2041-8205/735/2/L27 | volume=735 | issue=2 | journal=The Astrophysical Journal | page=L27 | bibcode=2011ApJ...735L..27A}}
19. ^{{cite journal | title=The Survival Rate of Ejected Terrestrial Planets with Moons | first=John H. | last=Debes | author2=Steinn Sigurðsson | date=20 October 2007 | journal=The Astrophysical Journal Letters | volume=668 | issue=2 | pages=L167–L170 | doi=10.1086/523103 | bibcode=2007ApJ...668L.167D | arxiv=0709.0945}}
20. ^{{cite journal | title=Spitzer Identification of the Least Massive Known Brown Dwarf with a Circumstellar Disk | first=Kevin L. | last=Luhman | date=10 February 2005 | journal=Astrophysical Journal Letters | volume=620 | issue=1 | pages=L51–L54 |doi=10.1086/428613 |bibcode=2005ApJ...620L..51L | arxiv=astro-ph/0502100}}
21. ^{{cite journal | title=Discovery of Young, Isolated Planetary Mass Objects in the σ Orionis Star Cluster | first=M. R. | last=Zapatero Osorio | date=6 October 2000 | journal=Science | volume=290 | issue=5489 | page=103 | doi=10.1126/science.290.5489.103 | bibcode=2000Sci...290..103Z}}
22. ^{{cite journal |title=Discovery of a Planetary-Mass Brown Dwarf with a Circumstellar Disk | first=Kevin L. | last=Luhman | date=10 December 2005 | journal=Astrophysical Journal Letters | volume=635 | issue=1 | pages=L93–L96 | doi=10.1086/498868 | bibcode=2005ApJ...635L..93L | arxiv=astro-ph/0511807}}
23. ^{{cite journal|first1=Étienne|last1=Artigau|first2=René|last2=Doyon|first3=David|last3=Lafrenière|first4=Daniel|last4=Nadeau|title=Discovery of the Brightest T Dwarf in the Northern Hemisphere|url=http://stacks.iop.org/1538-4357/651/i=1/a=L57|journal=The Astrophysical Journal Letters|date= n.d. |issn=1538-4357|pages=L57|volume=651|issue=1|doi=10.1086/509146|first5=Jasmin|last5=Robert|first6=Loïc|last6=Albert|arxiv=astro-ph/0609419}}
24. ^{{cite journal|first1=Jonathan|last1=Gagné|first2=Jacqueline K.|last2=Faherty|first3=Adam J.|last3=Burgasser|first4=Étienne|last4=Artigau|title=SIMP J013656.5+093347 is Likely a Planetary-Mass Object in the Carina-Near Moving Group|journal=The Astrophysical Journal|date=15 May 2017|issn=2041-8213|pages=L1|volume=841|issue=1|doi=10.3847/2041-8213/aa70e2|first5=Sandie|last5=Bouchard|first6=Loïc|last6=Albert|first7=David|last7=Lafrenière|first8=René|last8=Doyon|first9=Daniella C.|last9=Bardalez-Gagliuffi|arxiv=1705.01625}}
25. ^{{cite journal |title=A Young Planetary-Mass Object in the ρ Oph Cloud Core | first=Kenneth A. | last=Marsh | date=1 February 2010 | journal=Astrophysical Journal Letters | volume=709 | issue=2 | pages=L158–L162 | doi=10.1088/2041-8205/709/2/L158 | bibcode=2010ApJ...709L.158M | arxiv=0912.3774}}
26. ^{{cite journal | title=CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet in the young moving group AB Doradus? | first=Philippe | last=Delorme | date=25 September 2012 | journal=Astronomy & Astrophysics | volume=548A | page=26 |doi=10.1051/0004-6361/201219984 | bibcode=2012A&A...548A..26D |arxiv=1210.0305}}
27. ^{{cite journal | title=The Extremely Red, Young L Dwarf PSO J318.5338-22.8603: A Free-floating Planetary-mass Analog to Directly Imaged Young Gas-giant Planets | first=Michael C. | last=Liu | date=10 November 2013 | journal=Astrophysical Journal Letters | volume=777 | issue=1 | pages=L20 | doi=10.1088/2041-8205/777/2/L20 | bibcode=2013ApJ...777L..20L|arxiv=1310.0457}}
28. ^{{cite journal | title=BANYAN. II. Very Low Mass and Substellar Candidate Members to Nearby, Young Kinematic Groups with Previously Known Signs of Youth | first=Jonathan | last=Gagné | date=10 March 2014 | journal=Astrophysical Journal | volume=783 | issue=2 | page=121 | doi=10.1088/0004-637X/783/2/121 | bibcode=2014ApJ...783..121G | arxiv=1312.5864}}
29. ^{{cite journal | title=Discovery of the Young L Dwarf WISE J174102.78-464225.5 | first=Adam C. | last=Schneider | date=9 January 2014 | journal=Astronomical Journal | volume=147 | issue=2 | page=34 | doi=10.1088/0004-6256/147/2/34 | bibcode=2014AJ....147...34S |arxiv=1311.5941}}
30. ^{{cite journal | title=Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun | first=Kevin L. | last=Luhman | date=10 May 2014 | journal=Astrophysical Journal Letters | volume=786 | issue=2 | page=L18 |doi=10.1088/2041-8205/786/2/L18 |bibcode=2014ApJ...786L..18L | arxiv=1404.6501}}
31. ^{{cite journal | title=The Coolest Isolated Brown Dwarf Candidate Member of TWA | first=Jonathan | last=Gagné | date=10 April 2014 | journal=Astrophysical Journal Letters | volume=785 | issue=1 | page=L14 | doi=10.1088/2041-8205/785/1/L14 | bibcode=2014ApJ...785L..14G | arxiv=1403.3120}}
32. ^{{cite journal | title=The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs | first=Michael C. | last=Liu | date=9 December 2016 | journal=Astrophysical Journal | volume=833 | issue=1 | page=96 | doi=10.3847/1538-4357/833/1/96 | bibcode=2016ApJ...833...96L|arxiv=1612.02426}}
33. ^{{cite journal | title=SIMP J2154-1055: A New Low-gravity L4β Brown Dwarf Candidate Member of the Argus Association | first=Jonathan | last=Gagné | date=1 September 2014 | journal=Astrophysical Journal Letters | volume=792 | issue=1 | page=L17 | doi=10.1088/2041-8205/792/1/L17 | bibcode=2014ApJ...792L..17G | arxiv=1407.5344}}
34. ^{{cite journal | title=SDSS J111010.01+011613.1: A New Planetary-mass T Dwarf Member of the AB Doradus Moving Group | first=Jonathan | last=Gagné | date=20 July 2015 | journal=Astrophysical Journal Letters | volume=808 | issue=1 | page=L20 | doi=10.1088/2041-8205/808/1/L20 | bibcode=2015ApJ...808L..20G | arxiv=1506.04195}}
35. ^{{cite journal | title=The Nearest Isolated Member of the TW Hydrae Association is a Giant Planet Analog | first=Kendra | last=Kellogg | date=11 April 2016 | journal=Astrophysical Journal Letters | volume=821 | issue=1 | page=L15 | doi=10.3847/2041-8205/821/1/L15 | bibcode=2016ApJ...821L..15K | arxiv=1603.08529}}
36. ^{{cite journal | title=WISEA J114724.10-204021.3: A Free-floating Planetary Mass Member of the TW Hya Association | first=Adam C. | last=Schneider | date=21 April 2016 | journal=Astrophysical Journal Letters | volume=822 | issue=1 | page=L1 | doi=10.3847/2041-8205/822/1/L1 | bibcode=2016ApJ...822L...1S | arxiv=1603.07985}}
37. ^{{cite web | url=https://motherboard.vice.com/en_us/article/ev3dkj/rare-sighting-of-two-rogue-planets-that-do-not-orbit-stars | title=Rare Sighting of Two Rogue Planets That Do Not Orbit Stars | publisher=Motherboard | language=English | author=Becky Ferreira | date=9 Nov 2018 | accessdate=10 February 2019}}
38. ^{{cite web | url=http://blogs.discovermagazine.com/d-brief/2018/11/16/rogue-planets-discovered/#.XEeAI2l7mUk | title=These Two New 'Rogue Planets' Wander the Cosmos Without Stars | publisher=Discover Magazine | language=English | author=Jake Parks | date=16 November 2018 | accessdate=10 February 2019}}
39. ^{{cite web | url=http://www.astronomy.com/news/2018/11/rogue-one-and-two | title=Two free-range planets found roaming the Milky Way in solitude | publisher=Astronomy Magazine | language=English | author=Jake Parks | date=15 November 2018 | accessdate=10 February 2019}}
40. ^{{cite web | url=https://motherboard.vice.com/en_us/article/ev3dkj/rare-sighting-of-two-rogue-planets-that-do-not-orbit-stars | title=Rare Sighting of Two Rogue Planets That Do Not Orbit Stars | publisher=Motherboard | language=English | author=Becky Ferreira | date=9 Nov 2018 | accessdate=10 February 2019}}
41. ^{{cite web | url=http://blogs.discovermagazine.com/d-brief/2018/11/16/rogue-planets-discovered/#.XEeAI2l7mUk | title=These Two New 'Rogue Planets' Wander the Cosmos Without Stars | publisher=Discover Magazine | language=English | author=Jake Parks | date=16 November 2018 | accessdate=10 February 2019}}
42. ^{{cite web | url=http://www.astronomy.com/news/2018/11/rogue-one-and-two | title=Two free-range planets found roaming the Milky Way in solitude | publisher=Astronomy Magazine | language=English | author=Jake Parks | date=15 November 2018 | accessdate=10 February 2019}}

Bibliography

  • {{cite journal |last= Stevenson |first= D. |title= Life-sustaining planets in interstellar space? |journal= Nature |volume= 400 |page= 32 |date= 1999 |doi= 10.1038/21811 |pmid= 10403246 |issue= 6739|bibcode= 1999Natur.400...32S}}
  • [https://web.archive.org/web/20140529085818/http://mh-gps-p1.caltech.edu/uploads/File/People/djs/interstellar_planets.pdf Article by Stevenson similar to the Nature article but containing more information, titled: "Possibility of Life Sustaining Planets in Interstellar Space"]

External links

{{Wiktionary|Interstellar planet}}{{Commons category|Exoplanets}}
  • [https://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf Definition of a "Planet"] (Resolution B5 - IAU)
  • Strange New Worlds Could Make Miniature Solar Systems Robert Roy Britt (SPACE.com) 5 June 2006 11:35 am ET
  • [https://web.archive.org/web/20060820075858/http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html The IAU draft definition of "planet" and "plutons"] press release (International Astronomical Union) 2006
{{exoplanet}}{{portal bar|Astronomy|Space}}

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