 | ||
WISE 0855−0714 (full designation WISE J085510.83−071442.5) is a (sub-) brown dwarf 2.23±0.04 parsecs (7.27±0.13 light-years) from Earth announced in April 2014 by Kevin Luhman using data from the Wide-field Infrared Survey Explorer (WISE). As of 2014, WISE 0855−0714 has the third-highest proper motion (8118±8 mas/yr) after Barnard's Star (10300 mas/yr) and Kapteyn's Star (8600 mas/yr). As of 2014 it also has the fourth-largest parallax (449±8 mas) of any known star or brown dwarf, meaning it is the fourth closest extrasolar system to the Sun. It is also the coldest object of its type found in interstellar space, having a temperature in the range 225 to 260 K (−48 to −13 °C; −55 to 8 °F).
Contents
Observations
The WISE object was detected in March 2013 and follow-up observations were taken by the Spitzer Space Telescope and the Gemini North telescope. The name WISE J085510.83−071442.5 includes the coordinates and indicates that the object is located in the constellation Hydra.
Distance and proper motion
Based on direct observations WISE 0855−0714 has a large parallax, which specifically relates to its distance from the Solar System. This phenomenon results in a distance of around 7.27±0.13 light-years, with a small margin of error due to the strength of the parallax effect and the clarity of the observations. WISE 0855−0714's proper motion across the sky is also directly observed over time, which helped lead to its discovery as it "stood out" in the observations, but the proper motion is itself a combination of its speed in the galactic neighborhood relative to the Solar System as well as its proximity to the Solar System. If it were moving exactly as fast but farther away, if it were moving more slowly but closer, or if it were moving more quickly near to the Sun but moving at a high angle towards or away from the Sun, it would have a smaller proper motion.
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 4.6 µm at an apparent magnitude of 13.89±0.05, though it was brighter into the deeper infrared. Infrared images taken with the Magellan Baade telescope suggest evidence of water clouds.
Model-derived understanding
Based on models of brown dwarfs WISE 0855−0714's is estimated to have a mass of 3 to 10 MJup. This mass is in the range of a sub-brown dwarf or other planetary-mass object.
As of 2003, the International Astronomical Union considers an object with a mass above 13 MJup, capable of fusing deuterium, to be a brown dwarf. A lighter object and one orbiting another object is considered a planet. So far this WISE object is alone, though it could be a rogue planet, something first identified in 2004 in the case of Cha 110913-773444.
Combining its luminosity, distance, and mass it is estimated to be the coldest known brown dwarf, with a modeled effective temperature of 225 to 260 K (−48 to −13 °C; −55 to 8 °F), depending on the model.