WISEPA J173835.53+273258.9

WISEPA J173835.53+273258.9 (abbreviated WISE 1738+2732) is a brown dwarf of spectral class Y0, located in the constellation Hercules at 24.9 light-years from Earth.

Discovery
WISE 1738+2732 was discovered in 2011 from data, collected by the Wide-field Infrared Survey Explorer (WISE) Earth-orbiting satellite — NASA infrared-wavelength 40 cm (16 in) space telescope, which mission lasted from December 2009 to February 2011. WISE 1738+2732 has two discovery papers: Kirkpatrick et al. (2011) and Cushing et al. (2011), however, basically with the same authors and published nearly simultaneously.


 * Kirkpatrick et al. presented discovery of 98 new found by WISE brown dwarf systems with components of spectral types M, L, T and Y, among which also was WISE 1738+2732.
 * Cushing et al. presented discovery of seven brown dwarfs — one of T9.5 type, and six of Y-type — first members of the Y spectral class, ever discovered and spectroscopically confirmed, including "archetypal member" of the Y spectral class WISE 1828+2650, and WISE 1738+2732. These seven objects are also the faintest seven of 98 brown dwarfs, presented in Kirkpatrick et al. (2011).

Distance
Currently the most accurate distance estimate of WISE 1738+2732 is a trigonometric parallax, published in 2021 by Kirkpatrick et al.: $337.1$, corresponding to a distance of $-343.4$, or $450$.

Space motion
WISE 1738+2732 has a proper motion of $130.9 mas$ milliarcseconds per year.

Properties
The object's temperature estimate is 350 (350–400) K. Its spectrum is similar with spectrum of another Y-dwarf WISE 1405+5534.

Disequilibrium chemistry models suggest that this Y-dwarf has a low mass of about 3-9, making it a possible isolated planetary-mass object, together with WISE 0350-5658. A more recent paper finds a mass of 5-14.

WISE 1405 is variable in the near- and mid-infrared. The observations were made with the Gemini Observatory and Spitzer. It has a rotation period of 6.0±0.1 hours and the amplitude is 3% for 4.5 μm and may be as high as 5-30% in the near-infrared. This dependence on wavelength can be reproduced with patchy cloud layers made up of potassium chloride (KCl) and sodium sulfide (Na2S).