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WISE 0535−7500

Coordinates: Sky map 05h 35m 16.8s, −75° 00′ 24.9″
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WISE J053516.80−750024.9
Observation data
Epoch J2000[1]      Equinox J2000[1]
Constellation Mensa
Right ascension 05h 35m 16.8s[1]
Declination −75° 00′ 24.9″[1]
Characteristics
Spectral type ≥Y1[1]
Apparent magnitude (J (MKO-NIR filter system)) >21.1[1]
Apparent magnitude (H (MKO-NIR filter system)) >21.6[1]
Astrometry
Proper motion (μ) RA: -310 ± 128[2] mas/yr
Dec.: 159 ± 92[2] mas/yr
Parallax (π)250 ± 79 mas[2]
Distance13.0+6.0
−3.1[3] ly
(4.0+1.9
−-0.9[3] pc)
Other designations
WISE J053516.80−750024.9,[1]
WISE 0535−7500[1]
Hertzsprung-Russell diagram of all the nearest stars out to Gliese 1, as well as most brown dwarfs and some planets. WISE 0535−7500 is at bottom right

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 [1] located in constellation Mensa. It is estimated to be 13 light-years from Earth.[3] 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.

Discovery

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.[1]

Distance

Trigonometric parallax of WISE 0535−7500 is 0.250 ± 0.079 arcsec, corresponding to a direct inversion distance[3] of 4.0+1.9
−-0.9 pc and 13.0+6.1
−3.1 ly.

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
−1.2		 19.2+6.7
−3.9		 [1]
Marsh et al. (2013) 250 ± 79 21+13
−11		 68.5+42.4
−35.9		 [2]
Paterson (2015) 250 ± 79 4.0+1.9
−-0.9		 13.0+6.1
−3.1		 [3]

Non-trigonometric distance estimates are marked in italic. The best estimate is marked in bold.

Y dwarf

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.[4]

If planets are L dwarfs or T dwarfs then they must be both young (younger than 350 million years) and heavy.[4] 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.

References

  1. ^ a b c d e f g h i j k l 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:1205.2122. Bibcode:2012ApJ...753..156K. doi:10.1088/0004-637X/753/2/156.
  2. ^ a b c d 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:1211.6977. Bibcode:2013ApJ...762..119M. doi:10.1088/0004-637X/762/2/119.
  3. ^ a b c d e Paterson, David.A. "Topics in Astronomy: Topic 8. Inappropriateness of the Lutz-Kelker equation for brown dwarfs".
  4. ^ a b 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.
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