WISE J053516.80−750024.9 (designation abbreviated to WISE 0535−7500) is either a sub-brown dwarf or a free planet. It has spectral class Y1 and is located in constellation Mensa. It is estimated to be 47 light-years from Earth.
In 2017, more accurate analysis found it to be a binary system made up of two substellar objects of spectral class≥Y1 in orbit less than one astronomical unit from each other.
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 40cm (20inches) 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.
Trigonometric parallax of WISE 0535−7500 is 0.070 ± 0.005 arcsec, corresponding to a distance of 14 pc and 47 ly.
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 M dwarfs, 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.
WISE 0535−7500 was studied with JWST by Beiler et al. in 2024 together with 22 other late-T and Y-dwarfs. WISE 0535−7500 stands out due to it having no discernable CO2 band and an almost undetectable CO band. This could be due a low metallicity or high surface gravity. These features make this object extremely red in Spitzer colors. Other common prominent features like H2O, NH3 and CH4 are present in its spectrum. But like other late-T and Y-dwarfs it is missing PH3, which is predicted to occur for these objects.