PSO J318.5−22

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PSO J318.5−22
PSO J318.5-22 (red object) imaged by the Pan-STARRS PS1 telescope in 2013
Discovery sitePan-STARRS PS1 telescope, Haleakalā
Discovery date2013
Direct imaging
2MASS J21140802-2251358,
PSO J318.5338-22.8603,
TIC 24266526,
WISE J211408.13-225137.3
Physical characteristics
Mean radius
1.38±0.02 RJ[1][2]
Mass6.92±0.68 MJ[1][2]
8.6±0.1 h[3]
56.2±8.1° (to plane of sky)[3]
Temperature1275 K[4]
Spectral type
NASA Exoplanet Exploration Program "travel poster" for PSO J318.5-22

PSO J318.5−22 is a rogue planet, an extrasolar object of planetary mass that does not orbit a parent star.[5][6] It is approximately 80 light-years away and belongs to the Beta Pictoris moving group.[7] The object was discovered in 2013 in images taken by the Pan-STARRS PS1 wide-field telescope. PSO J318.5-22's age is inferred to be 12 million years, the same age as the Beta Pictoris group.[8] Based on its calculated temperature and age, it is classified under the brown dwarf spectral type L7.[9]

The team leader, Michael Liu of the Institute for Astronomy at the University of Hawaii, stated, "We have never before seen an object free-floating in space that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone."[10] Current theories about such objects include the possibility that gravitational perturbations may have kicked them out of their planetary systems soon after they formed through planetary accretion, or they may have been formed by some other means.[11] Estimated temperatures inside its clouds exceed 1,100 K (800 °C). The clouds, made of hot dust and molten iron, show how widespread clouds are in planets and planet-like objects.[12] However, by 2020, modeling showed that the brightness variability could not be unambiguously attributed to clouds.[4]

See also[edit]


  1. ^ a b Sanghi, Aniket; Liu, Michael C.; Best, William M.; Dupuy, Trent J.; Siverd, Robert J.; Zhang, Zhoujian; Hurt, Spencer A.; Magnier, Eugene A.; Aller, Kimberly M.; Deacon, Niall R. (6 September 2023). "The Hawaii Infrared Parallax Program. VI. The Fundamental Properties of 1000+ Ultracool Dwarfs and Planetary-mass Objects Using Optical to Mid-IR SEDs and Comparison to BT-Settl and ATMO 2020 Model Atmospheres". ApJ: 51. arXiv:2309.03082.
  2. ^ a b Sanghi, Aniket; Liu, Michael C.; Best, William M.; Dupuy, Trent J.; Siverd, Robert J.; Zhang, Zhoujian; Hurt, Spencer A.; Magnier, Eugene A.; Aller, Kimberly M.; Deacon, Niall R. (7 September 2023). "Table of Ultracool Fundamental Properties". Zenodo: 1.
  3. ^ a b Biller, Beth; Vos, Johanna; Buenzli, Esther; Allers, Katelyn; Bonnefoy, Mickaël; Charnay, Benjamin; Bézard, Bruno; Allard, France; Homeier, Derek; Bonavita, Mariangela; Brandner, Wolfgang; Crossfield, Ian; Dupuy, Trent; Henning, Thomas; Kopytova, Taisiya; Liu, Michael C.; Manjavacas, Elena; Schlieder, Joshua (2018), "Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22", The Astronomical Journal, 155 (2): 95, arXiv:1712.03746, doi:10.3847/1538-3881/aaa5a6, S2CID 119200240
  4. ^ a b Tremblin, P.; Phillips, M. W.; Emery, A.; Baraffe, I.; Lew, B. W. P.; Apai, D.; Biller, B. A.; Bonnefoy, M. (2020), "Rotational spectral modulation of cloudless atmospheres for L/T brown dwarfs and extrasolar giant planets", Astronomy & Astrophysics, 643: A23, arXiv:2009.06269, doi:10.1051/0004-6361/202038771, S2CID 221655776
  5. ^ "Gemini Confirms Lonely Planet Floating in Space". Gemini Observatory. 7 October 2013.
  6. ^ "Astronomers using Hawaii telescopes discover planet without a star". Honolulu Star-Advertiser. 9 October 2013. Archived from the original on 14 October 2013. Retrieved 9 October 2013.
  7. ^ "A Strange Lonely Planet Found Without a Star". ScienceDaily. 9 October 2013.
  8. ^ "A Strange Lonely Planet Found without a Star". Institute for Astronomy, University of Hawaii. 9 October 2013.
  9. ^ Michael C. Liu; Eugene A. Magnier; Niall R. Deacon; Katelyn N. Allers; et al. (1 October 2013). "The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets". Astrophysical Journal Letters. 777. arXiv:1310.0457. Bibcode:2013ApJ...777L..20L. doi:10.1088/2041-8205/777/2/L20. S2CID 54007072.
  10. ^ "Young planet, six times more massive than Jupiter, found hanging alone without star". Pentagon Post. 10 October 2013. Archived from the original on 4 March 2022. Retrieved 4 March 2022.
  11. ^ Boyle, Alan (9 October 2013). "Astronomers say they've spotted lonesome planet without a sun". NBC News. Retrieved 4 March 2022.
  12. ^ "Edinburgh University astronomers find sunless world". BBC News. 3 November 2015.