Epoch J2000 Equinox J2000
|Right ascension||05h 35m 16.8s|
|Declination||−75° 00′ 24.9″|
|Apparent magnitude (J (MKO-NIR filter system))||>21.1|
|Apparent magnitude (H (MKO-NIR filter system))||>21.6|
|Proper motion (μ)||RA: -310 ± 128 mas/yr
Dec.: 159 ± 92 mas/yr
|Parallax (π)||250 ± 79 mas|
WISE J053516.80−750024.9 (designation abbreviated to WISE 0535−7500) is either a brown dwarf or a free planet. It has spectral class ≥Y1 and is  located in constellation Mensa. It is estimated to be 13 light-years from Earth. As of October 2015, that makes it the third-nearest Y dwarf, after WISE 0855−0714 and WISE 0350−5658. It is nearer than all but four naked eye stars, and the 31st-nearest star system to the Solar System. If a free planet, it is the second-nearest, the nearest being WISE 0855−0714. If a brown dwarf, then it is the ninth-nearest brown dwarf.
WISE 0535−7500 was discovered in 2012 by J. Davy Kirkpatrick et al. from data, collected by Wide-field Infrared Survey Explorer (WISE) Earth-orbiting satellite — NASA infrared-wavelength 40-centimetre (16 in) space telescope, which mission lasted from December 2009 to February 2011. In 2012 Kirkpatrick et al. published a paper in The Astrophysical Journal, where they presented the discovery of seven new found by WISE brown dwarfs of spectral type Y, among which also was WISE 0535−7500.
WISE 0535−7500 distance estimates
|Source||Parallax, mas||Distance, pc||Distance, ly||Ref.|
|Marsh et al. (2013)
(according to Kirkpatrick et al. (2012))
|170 ± 44||5.9+2.1
|Marsh et al. (2013)||250 ± 79||21+13
|Paterson (2015)||250 ± 79||4.0+1.9
Non-trigonometric distance estimates are marked in italic. The best estimate is marked in bold.
Brown dwarfs are defined as substellar objects that have at some time in their lives burnt deuterium in their interior. The borderline between a brown dwarf and a planet is conventionally taken to be 13 times the mass of Jupiter. All brown dwarfs are either L dwarfs, T dwarfs or Y dwarfs, in order of decreasing temperature. An increasing number after the letter in the spectral type also means decreasing temperature, a Y2 dwarf is cooler than a Y1 dwarf is cooler than a Y0 dwarf. Planets can also be L dwarfs, T dwarfs or Y dwarfs.
If planets are L dwarfs or T dwarfs then they must be both young (younger than 350 million years) and heavy. The cooler a Y dwarf, the higher the likelihood that it is a planet. WISE 0535-7500 is the second-nearest Y dwarf that could be of a type cooler than Y1, so could easily be the second-nearest free planet to Earth. Of the two nearer Y dwarfs, WISE 0855−0714 has an effective temperature below the freezing point of water, and WISE 0350−5658 has an effective temperature above the boiling point of water. WISE 0535−7500 is of a spectral type between that of WISE 0855−0714 and WISE 0350−5658 so the possibility exists that it may in the correct temperature range for liquid water to exist on its surface.
- Kirkpatrick, J. D.; Gelino, C. R.; Cushing, M. C.; Mace, G. N.; Griffith, R. L.; Skrutskie, M. F.; Marsh, K. A.; Wright, E. L.; Eisenhardt, P. R.; McLean, I. S.; Mainzer, A. K.; Burgasser, A. J.; Tinney, C. G.; Parker, S.; Salter, G. (2012). "Further Defining Spectral Type "Y" and Exploring the Low-mass End of the Field Brown Dwarf Mass Function". The Astrophysical Journal. 753 (2): 156. arXiv: . Bibcode:2012ApJ...753..156K. doi:10.1088/0004-637X/753/2/156.
- Marsh, Kenneth A.; Wright, Edward L.; Kirkpatrick, J. Davy; Gelino, Christopher R.; Cushing, Michael C.; Griffith, Roger L.; Skrutskie, Michael F.; Eisenhardt, Peter R. (2013). "Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T". The Astrophysical Journal. 762 (2): 119. arXiv: . Bibcode:2013ApJ...762..119M. doi:10.1088/0004-637X/762/2/119.
- Paterson, David.A. "Topics in Astronomy: Topic 8. Inappropriateness of the Lutz-Kelker equation for brown dwarfs".
- I. Neill Reid and Stanimir A. Metchev, Chapter 5: The Brown Dwarf – Exoplanet Connection, in John W. Mason (ed.) Exoplanets: Detection, Formation, Properties, Habitability; Springer, Berlin, 2008.