Planets not gravitationally bound to a star
This video shows an artist's impression of the free-floating planet CFBDSIR J214947.2-040308.9 .
A rogue planet , also termed a free-floating planet (FFP ) or an isolated planetary-mass object (iPMO ), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf .[ 1] [ 2] [ 3] [ 4]
Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system. The Milky Way alone may have billions to trillions of rogue planets, a range the upcoming Nancy Grace Roman Space Telescope is expected to refine.[ 5] [ 6]
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 .[ 7] A possible example is Cha 110913−773444 , which may either have been ejected and become a rogue planet or formed on its own to become a sub-brown dwarf.[ 8]
^ Shostak, Seth (24 February 2005). "Orphan Planets: It's a Hard Knock Life" . Space.com . Retrieved 13 November 2020 .
^ Lloyd, Robin (18 April 2001). "Free-Floating Planets – British Team Restakes Dubious Claim" . Space.com . Archived from the original on 13 October 2008.
^ "Orphan 'planet' findings challenged by new model" . NASA Astrobiology. 18 April 2001. Archived from the original on 22 March 2009.
^ Kirkpatrick, J. Davy; Gelino, Christopher R.; Faherty, Jacqueline K.; Meisner, Aaron M.; Caselden, Dan; Schneider, Adam C.; Marocco, Federico; Cayago, Alfred J.; Smart, R. L.; Eisenhardt, Peter R.; Kuchner, Marc J.; Wright, Edward L.; Cushing, Michael C.; Allers, Katelyn N.; Bardalez Gagliuffi, Daniella C. (1 March 2021). "The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs" . The Astrophysical Journal Supplement Series . 253 (1): 7. arXiv :2011.11616 . Bibcode :2021ApJS..253....7K . doi :10.3847/1538-4365/abd107 . ISSN 0067-0049 .
^ Neil deGrasse Tyson in Cosmos: A Spacetime Odyssey as referred to by National Geographic
^ "The research team found that the mission will provide a rogue planet count that is at least 10 times more precise than current estimates, which range from tens of billions to trillions in our galaxy." https://scitechdaily.com/our-solar-system-may-be-unusual-rogue-planets-unveiled-with-nasas-roman-space-telescope/
^ Working Group on Extrasolar Planets – Definition of a "Planet" Position Statement on the Definition of a "Planet" (IAU) Archived 16 September 2006 at the Wayback Machine
^ "Rogue planet find makes astronomers ponder theory"