WISE 0855−0714

WISE 0855−0714 was first imaged by the WISE telescope on 4 May 2010 during its primary mission of surveying the entire sky. It was later discovered by Kevin Luhman in March 2013, who noticed the object's unusually high proper motion while searching for potential binary companions of the Sun in WISE images. In the interest of confirming the object's spectral properties and nearby distance to the Sun, Luhman made follow-up observations with the Spitzer Space Telescope and the Gemini North telescope in 2013–2014. The discovery of the object was announced in a NASA press release in April 2014. == Distance and proper motion ==

Based on direct observations, WISE 0855−0714 has a large parallax of , which corresponds to a distance of around (). This makes WISE 0855−0714 the fourth-closest stellar or substellar system to the Sun. WISE 0855−0714 also has an exceptionally high proper motion of , the third-highest after Barnard's Star () and Kapteyn's Star () == Physical characteristics ==

Mass and age The mass and age of WISE 0855−0714 are neither known with certainty, but can be constrained with its known present-day temperature. The age of WISE 0855−0714 depends on its mass; a lower mass would lead to a faster rate of cooling and thus a younger age for WISE 0855−0714, whereas a higher mass would lead to a slower rate of cooling and thus an older age for WISE 0855−0714. although the literature classifies it as a brown dwarf. If the distinction is based on how the object formed then it might be considered a failed star, a theory advanced for the object Cha 110913-773444. Size and temperature WISE 0855-0714 is the coldest-known brown dwarf, with an estimated effective temperature of , as estimated from evolutionary models based on its bolometric luminosity of and an assumed age between 1 and 10 billion years. Atmospheric models matching the NIRSpec spectrum are well fitted with a temperature of , somewhat lower than that estimated from evolution models. The bolometric luminosity and the 285 K effective temperature imply a radius of , smaller than the predicted by evolutionary models. Luminousity and radiation Since WISE 0855−0714 is an isolated object, its luminosity primarily comes from thermal radiation. WISE 0855−0714's temperature is low enough that it roughly matches room temperature, which means WISE 0855−0714's luminosity is very low and it primarily emits infrared radiation as thermal radiation. Hence, it is best observed with infrared telescopes such as WISE and the James Webb Space Telescope (JWST). WISE 0855−0714 has been detected in spectral wavelengths as short as —in this near-infrared wavelength, the object appears extremely dim with an apparent magnitude of 26.3. WISE 0855−0714's brightness decreases with decreasing wavelength, so the object is practically invisible in visible light. == Spectrometry ==

Its luminosity in different bands of the thermal infrared in combination with its absolute magnitude—because of its known distance—was used to place it in context of different models; the best characterization of its brightness was in the W2 band of at an apparent magnitude of , though it was brighter into the deeper infrared. Observations with NIRSpec detected methane (CH4), water vapor (H2O), ammonia (NH3) and carbon monoxide (CO) in the atmosphere, but was not able to confirm any phosphine (PH3) or carbon dioxide (CO2) in the atmosphere. Water ice clouds are also not confirmed and the spectrum is well matched with a cloudless model. In November 2024 a team used archived and new NIRSpec data to detect deuterated methane (CH3D) and about one part per billion PH3 in WISE 0855. This detection of deuterium showed that WISE 0855 has a mass below the deuterium-burning-limit. The low amount of PH3 is on the other hand in disagreement with predictions, showing incomplete knowledge of phosphorus chemistry. == Variability ==

Variability of WISE 0855 in the infrared was measured with Spitzer IRAC. A relative small amplitude of 4–5% was measured. Water ice cloud models predicted a large amplitude. This small amplitude might suggest that the hemispheres of WISE 0855 have very small deviation in cloud coverage. The light curve is too irregular to produce a good fit and rotation periods between 9.7 and 14 hours were measured. == Search for satellites ==

A team of researchers used 11 hours of JWST observations to search for transits caused by exomoons around WISE 0855. The researchers did not find any transits. By injecting transits into the light curve, the researchers found that they could have detected ≥0.5% deep transits with a detection rate of 96%. This transit depth would be seen for an object about twice as large as Saturn's moon Titan. == Gallery ==

File:WISE J085510.83–071442.5 movement (PIA18002).gif|Time-lapsed photo sequence of WISE 0855−0714's movement in the sky using captured images from the WISE and the Spitzer telescopes. File:WISE 0855-0714 NIRCam Movement.jpg|JWST NIRCam observation of W0855 (orange "star" at the center) showing the movement over about half a year. File:PIA18003-NASA-WISE-StarsNearSun-20140425-2 correction.png|Diagram of the closest stars to the Sun within 7.5 ly. File:Angular map of fusors around Sol within 9ly (large).png|The position of WISE 0855−0714 on a radar map among all stellar objects or stellar systems within 9 light years (ly) from the map's center, the Sun (Sol). The diamond-shapes are their positions entered according to right ascension in hours angle (indicated at the edge of the map's reference disc), and according to their declination. The second mark shows each's distance from Sol, with the concentric circles indicating the distance in steps of one ly. File:Class-iii cubicapoc.png|No water ice clouds are detected in WISE 0855, but deep ammonium dihydrogen phosphate clouds may exist. This would make it similar to class III (cloudless) planets on the Sudarsky scale ==See also==