Using a combination of the Subaru Telescope, Keck Observatory and ESA's Gaia mission, astronomers photographed a brown dwarf companion around the M dwarf star LSPM J1446+4633.
NIRC2 image of J1446 taken in August 2023; the white arrow indicates the location of the new J1446B companion. Image credit: Uyama etc.., doi: 10.3847/1538-3881/ae08b6.
LSPM J1446+4633 (hereinafter J1446) is one of the closest medium-M dwarfs at a distance of 17 parsecs (55 light years).
The newly discovered brown dwarf orbits the star at a distance approximately 4.3 times the distance between Earth and the Sun, completing one orbit every about 20 years.
The object, dubbed J1446B, has a mass 20 to 60 times that of Jupiter.
“The key to this discovery was the combination of three complementary observing techniques: (i) radial velocity (RV) measurements from long-term infrared spectroscopic monitoring using the Subaru IRD instrument, (ii) high-resolution near-infrared imaging from the W.M. Keck Observatory using advanced adaptive optics with a pyramidal wavefront sensor; and (iii) precise astrometric acceleration measurements with ESA's Gaia mission,” said California State University astronomer Taichi Uyama and colleagues.
“By integrating these data sets and applying Kepler's laws“We were able to determine the dynamic mass and orbital parameters of J1446B with unprecedented accuracy.”
“Radial velocity data alone cannot resolve the degeneracy between mass and orbital inclination, but the addition of direct imaging and Gaia astrometry resolves this ambiguity.”
“The Subaru IRD-SSP program provided critical RV data, and state-of-the-art Keck adaptive optics enabled direct detection of the satellite at a very close distance from its parent star.”
“Previous studies have demonstrated the effectiveness of combining Hipparcos and Gaia astrometric acceleration with direct imaging for satellite detection and characterization.”
“However, Hipparcos was unable to measure the positions of dim red dwarfs such as J1446.”
“Our study is the first to apply Gaia-only acceleration data to such a system, successfully constraining the orbit and dynamical mass of a brown dwarf companion.”
Near-infrared observations of J1446B revealed brightness changes of about 30%, indicating dynamic atmospheric phenomena such as clouds or storms.
“This discovery provides a critical benchmark for testing brown dwarf formation scenarios and atmospheric models,” the astronomers said.
“Future spectroscopic observations may even allow researchers to map the weather patterns of this intriguing object.”
“The result highlights the potential of combining ground-based and space-based observatories to discover hidden worlds beyond our solar system.”
teams paper was published in Astronomical Journal.
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Taichi Uyama etc.. 2025. Direct imaging studies for satellites from the Subaru/IRD II strategic program; Discovery of a brown dwarf companion around the neighboring medium-M dwarf LSPM J1446+4633. A.J. 170, 272; two: 10.3847/1538-3881/ae08b6
