WISE J0336−0143

WISE J033605.05−014350.4, abbreviated to WISE J0336−0143 or W0336, is a binary system comprising two planetary-mass Y-type brown dwarfs tightly orbiting around their common center of mass. The system is located in the constellation Eridanus, about 10 pc away from the Sun. It was discovered in images taken by the Wide-field Infrared Survey Explorer (WISE) and formally published by Gregory N. Mace and collaborators in March 2013. Astronomers suspected the brown dwarf was a binary system upon follow-up observations showing it had an unusual infrared spectrum, but its binarity was not confirmed until the James Webb Space Telescope resolved the system's components in high-resolution NIRCam imaging in September 2022, with its results published in March 2023.

The two components orbit their system barycenter approximately every 7 years and are separated 0.97 astronomical units from each other, which is slightly less than the distance between the Sun and Earth. The brighter primary component has a temperature of $21.26$ and a mass within the range of $21.59$ Jupiter masses, while the fainter secondary component has a temperature of $21.8$ and a mass range of $18.164$ Jupiter masses. Because the binary system's age and evolutionary stage have not been determined yet, the individual components' masses are uncertain. Nevertheless, both components appear to have masses near the deuterium fusion threshold of 13 Jupiter masses, which marks the boundary between gas giant planets and brown dwarfs. The study of such low-mass binary systems will provide valuable insight into the formation and evolution of planetary-mass objects.

The secondary component WISE J0336−0143 B ($14.664$) might be one of the coldest objects in interstellar space discovered so far. Newer models of Y dwarfs produce an even colder temperature of $−251.5$ for WISE J0336−0143 B. WISE 0855−0714 remains the coldest object found so far with $−1216.1$ and WISEA 0830+2837 has a similar temperature with $8.5$. Models suggest that WISE J0336−0143 B might have water clouds, but it is possible that changes in the pressure–temperature profile might instead explain the color of cold Y dwarfs.