Using the Subaru Telescope and the Keck II telescope at the W. M. Keck Observatory, astronomers have discovered and directly imaged a brown dwarf orbiting HD 33632Aa, a Sun-like star located 86 light-years away in the constellation of Auriga.
HD 33632Ab detections in 2020 (top panels) and 2018 (bottom panels). Image credit: Currie et al., doi: 10.3847/2041-8213/abc631.
Brown dwarfs are cool, dim objects that have a size between that of a gas giant and that of a Sun-like star.
Sometimes called failed stars, these objects are too small to sustain hydrogen fusion reactions at their cores, yet they have star-like attributes.
Typically, brown dwarfs have masses between 11-16 Jupiters (the approximate mass at which deuterium fusion can be sustained) and 75-80 Jupiters (the approximate mass to sustain hydrogen fusion).
“This is the first time we have found a brown dwarf by looking around a star that is being tugged across the sky,” said Dr. Timothy Brandt, a researcher in the Department of Physics at the University of California, Santa Barbara.
“Finding a brown dwarf always involves luck, but this time we were able to stack the odds.”
Dr. Brandt and colleagues observed the HD 33632 system using powerful adaptive optics (AO) technology at Subaru Telescope’s state-of-the art exoplanet imaging system, SCExAO/CHARIS, and Keck Observatory’s advanced AO paired with its Near-Infrared Camera (NIRC2).
“These technologies remove the atmospheric blurring that distorts astronomical images, resulting in sharper images,” the astronomers said.
The images of the HD 33632 system show a brown dwarf about 20 AU (astronomical units) from the host star.
Named HD 33632Ab, the object has a mass of about 46 Jupiters and likely contains water and carbon monoxide in its atmosphere.
“Thanks to SCExAO/CHARIS’s incredibly sharp images, we can not only see HD 33632Ab but get ultra-precise measurements for its position and its spectrum, which gives important clues about its atmospheric properties and its dynamics,” said lead author Dr. Thayne Currie, an astronomer at the National Astronomical Observatory of Japan.
“Keck Observatory’s NIRC2 thermal infrared data allowed us to better understand how HD 33632Ab’s atmosphere compares to those of the first directly imaged exoplanets, HR 8799bcde, which were discovered in part by Keck.”
“By studying HD 33632Ab and the HR 8799 exoplanets, we hope to learn more about how atmospheric conditions of planets and brown dwarfs are tied to the diversity of their age and compositions, such as mass, temperatures, and chemical properties.”
The findings were published in the Astrophysical Journal Letters.
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Thayne Currie et al. 2020. SCExAO/CHARIS Direct Imaging Discovery of a 20 AU Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star. ApJL 904, L25; doi: 10.3847/2041-8213/abc631
