Get ready to embark on an exciting journey into the cosmos! We're about to uncover some incredible discoveries that will leave you in awe.
Unveiling New Worlds: A Revolutionary Telescope's First Findings
An international team of astronomers has made a groundbreaking announcement, revealing the discovery of two extraordinary substellar companions orbiting distant stars. This revelation marks the initial results from the Subaru Telescope's OASIS (Observing Accelerators with SCExAO Imaging Survey) program, a mission dedicated to exploring and characterizing massive planets and brown dwarfs.
But here's where it gets controversial... only about 1% of stars host these massive celestial bodies that can be directly photographed by current telescopes. Even in young planetary systems where these objects are still glowing hot, they remain elusive due to their faintness compared to their host stars.
So, where do we look? That's where OASIS steps in. By utilizing measurements from the European Space Agency's Hipparcos and Gaia missions, OASIS identifies stars influenced by the gravity of unseen companions. It then employs the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system to capture these hidden companions, providing the precision and technology needed for this challenging task.
"With OASIS, we're uncovering a whole new world of massive planets and brown dwarfs around stars we never thought to explore," says Thayne Currie, the Principal Investigator of OASIS at The University of Texas at San Antonio (UTSA).
Figure 1: A time-lapse movie showcasing the Subaru Telescope's images leading to the discovery of HIP 54515 b. The planet's host star is blocked, with its position marked by a star symbol. The dotted line outlines the mask used to block the star. High-resolution images from December 30, 2022, and February 20, 2024, are available via the provided links. (Credit: T. Currie/Subaru Telescope, UTSA)
The first discovery, HIP 54515 b, is a gas giant with a mass nearly 18 times that of Jupiter, orbiting a star twice the mass of our Sun. This planet orbits its star at a distance similar to that between Neptune and the Sun, which is an impressive feat considering the system's distance from Earth - a whopping 275 light-years!
"HIP 54515 b was captured just 0.15 arc-seconds from its star. That's like trying to see a baseball from 100 km away! It required the sharpest images enabled by Maunakea and SCExAO's advanced technology," Currie explains.
HIP 54515 b's orbit is slightly less circular than those of lower-mass Jupiter-like planets, suggesting a unique formation history compared to our Solar System's gas giants.
The second discovery, HIP 71618 B, orbits a similar two-solar-mass star but is a brown dwarf - an object that forms like a star but lacks the mass to sustain nuclear fusion. HIP 71618 B is about 60 times more massive than Jupiter, follows an elongated, elliptical orbit, and is crucial for future searches for Earth-like planets.
And this is the part most people miss... HIP 71618 B meets the requirements for the Roman Space Telescope's Coronagraph Instrument technology demonstration, planned for 2027. This experiment will be the first of its kind, testing advanced planet imaging technologies to suppress the glare of Sun-like stars and reveal rocky, Earth-like planets that are ten billion times fainter.
The discoveries of HIP 54515 b and HIP 71618 B highlight the power of combining space-based precision star-tracking with ground-based direct imaging. The OASIS program continues its survey, with more discoveries expected to deepen our understanding of planet and brown dwarf formation and atmospheric evolution. These findings will also contribute to the development of technologies for detecting habitable, Earth-like worlds.
"Subaru Telescope, with its innovative instruments and world-leading observing conditions on Maunakea, will remain a preeminent observatory, making groundbreaking discoveries for years to come," says Dr. Masayuki Kuzuhara (Astrobiology Center), who co-leads OASIS with Currie.
These groundbreaking results were published in Currie & Li et al. and El Morsy et al. on December 3, 2025, in the Astronomical Journal and Astrophysical Journal Letters, respectively.
OASIS is an international collaboration supported by the National Science Foundation and NASA, involving astronomers from institutions across the United States, Japan, Canada, Chile, and Europe.
The Subaru Telescope, operated by the National Astronomical Observatory of Japan, is a testament to the power of collaboration and innovation in astronomy.
