Free Astronomy Magazine January-February 2026

6 JANUARY-FEBRUARY 2026 ASTRO PUBLISHING standing the processes of stel- lar and planetary formation and evolution. However, be- cause M dwarfs are intrinsically faint, detailed observations have historically been limited, and early surveys suggested that more than 70% of them were single stars. Recent ad- vances in observational tech- niques have revealed this observation to be incomplete: the frequency of low-mass stel- lar and substellar companions, such as brown dwarfs, may have been significantly under- estimated. Understanding how often such companions occur— and their mass distribution—is essen- tial for distinguishing the similarities and differences between planet for- mation and star formation. The key to this discovery was a three- pronged observational approach in- cluding Keck Observatory, Subaru Telescope and the Gaia Mission: (1) radial velocity measurements from long-term infrared spectroscopic monitoring with Subaru’s InfraRed Doppler (IRD) tracked the subtle from the companion star. By integrating these datasets and applying Kepler’s laws, the team was able to determine the dynamical mass and or- bital parameters of J1446B with unprecedented accuracy. “Keck’s critical contribution was to make direct images of this Brown Dwarf companion which led to characterizing the object’s orbit and physical properties such as mass and temperature,” said Charles Beichman, Executive Director of the NASA Exoplanet Sci- ence Institute (NExScI) at Cal- tech and co-author of the study. The discovery of J1446B pro- vides a critical benchmark for testing brown dwarf formation scenarios and atmospheric models. Combining future Gaia Data Releases and ad- vanced spectroscopic data obtained from follow-up observations with new instrumentation – such as Keck Observatory’s HISPEC (High-resolu- tion Infrared Spectrograph for Exo- planet Characterization) may enable researchers to map weather pat- terns, providing a step toward understanding planet formation and evolution. Perhaps, even, guiding us to a planet like our own. Added Beichman, “Re- markably, two Keck im- ages showed variability in the Brown Dwarf’s brightness suggesting the existence of clouds and weather patterns! This combined ap- proach will become more and more power- ful, reaching down to the realm of gas giant planets like our own Jupiter, as new Keck in- strumentation comes into operation.” I nfrared image of the brown dwarf companion J1446B (marked by the arrow). The host star (J1446) is masked in white during image process- ing. The white bar at the lower right corresponds to an angular distance equiv- alent to 10 astronomical units (roughly the distance between Saturn and the Sun). [Taichi Uyama (Astro- biology Center/CSUN) / W. M. Keck Observatory] O rbit modeling of J1446B. (Left) The projected orbit inferred from W. M. Keck Observatory’s direct imaging (blue dot at upper right) and the acceleration in the host star’s motion measured by Gaia (red arrow). Axes show right ascension and declination in arcseconds. The black curve represents the most probable orbit, while the colored curves indicate other possible orbits; color corresponds to the estimated mass of J1446B (color scale shown on right). (Right) Radial velocity variations of the host star measured by IRD (red points), along with simulated orbital solutions color-coded by com- panion mass. The lower panel shows residuals from the fit. [Qier An (UCSB) / Uyama et al. (2025)] ! wobble of the host star, caused by their mutual gravitational pull; (2) high-resolution near-infrared imag- ing from Keck Observatory’s state-of- the-art adaptive optics on its Near-Infrared camera (NIRC2) en- abled the direct detection of the companion at a very small separa- tion from its host star; and (3) the Gaia mission tracked tiny changes in the star’s position in the sky to fur- ther reveal the gravitational pull