Subaru Telescope's OASIS Program Unveils New Worlds, Paving Way for NASA's Roman Mission

Astronomers utilizing the advanced Subaru Telescope in Hawaiʻi have announced their initial breakthroughs from the Observing Accelerators with SCExAO Imaging Survey (OASIS) program, according to a December 4, 2025, report from the National Astronomical Observatory of Japan (NAOJ). This groundbreaking effort has successfully identified a massive new planet and a brown dwarf orbiting distant stars, marking a significant step in exoplanet research.

The discoveries include a massive new planet designated HIP 54515 b and a brown dwarf named HIP 71618 B. These celestial bodies were found through a novel combination of space-based astrometry and high-contrast imaging, as detailed by Space Daily on December 5, 2025.

These findings are particularly crucial for advancing technologies destined for NASA's upcoming Nancy Grace Roman Space Telescope, which is slated for launch by May 2027, nasa confirmed in a December 4, 2025, press release. The Roman mission aims to directly image Earth-like exoplanets, and these new discoveries provide vital test targets.

The OASIS program, an international collaboration, leverages data from European Space Agency missions like Hipparcos and Gaia to pinpoint stars exhibiting gravitational tugs from unseen companions, astrobiology reported on December 8, 2025. Subsequently, the Subaru Telescope's advanced SCExAO system is employed to capture precise images of these hidden objects.

Notably, the brown dwarf HIP 71618 B possesses properties that make it an ideal candidate for testing the Roman Space Telescope's Coronagraph Instrument, as highlighted by NAOJ. Prior to this, astronomers lacked a confirmed target that met the stringent requirements for this critical technology demonstration.

The success of the OASIS program underscores the effectiveness of combining diverse observational techniques to uncover worlds previously obscured by stellar glare. These initial discoveries promise to deepen our understanding of planetary formation and atmospheric evolution, according to a December 3, 2025, article from UT San Antonio Today.

• The Subaru Telescope, operated by the National Astronomical Observatory of Japan (NAOJ), is an 8.2-meter optical-infrared telescope situated atop Maunakea, Hawaiʻi. Known for its wide field of view and advanced adaptive optics system, it is a premier instrument for exoplanet research, as described on the NAOJ website. Its location on Maunakea provides exceptional viewing conditions due to high altitude and stable atmospheric conditions.

• The OASIS program, or "Observing Accelerators with SCExAO Imaging Survey," represents a sophisticated approach to exoplanet detection. It begins by analyzing astrometric data from ESA's Hipparcos and Gaia missions, which measure minute shifts in stellar positions caused by the gravitational pull of orbiting companions, as explained by The Daily Galaxy on December 5, 2025. These "tugged stars" are then targeted by the Subaru Telescope's Coronagraphic Extreme Adaptive Optics (SCExAO) system, which uses advanced techniques to suppress the overwhelming brightness of the host star, allowing for direct imaging of faint companions.

• The newly discovered planet, HIP 54515 b, is a gas giant with a mass nearly 18 times that of Jupiter, orbiting a star approximately twice the mass of our Sun. Located about 275 light-years away in the constellation Leo, it maintains an orbit similar in distance to Neptune's path around our Sun, according to naoJ. Its close angular separation from its host star, akin to viewing a baseball from 100 kilometers away, pushed the limits of current direct imaging technology, requiring the SCExAO system's exceptional precision.

• HIP 71618 B is classified as a brown dwarf, an object intermediate in mass between giant planets and stars, with approximately 60 times the mass of Jupiter. Brown dwarfs are substellar objects that are not massive enough to sustain hydrogen fusion in their cores but can briefly fuse deuterium, as noted by Britannica. This particular brown dwarf, located 169 light-years away, orbits a two-solar-mass star with a high eccentricity and an average distance slightly larger than Saturn's orbit, according to naoJ.

• The discoveries are pivotal for NASA's Nancy Grace Roman Space Telescope, particularly for its Coronagraph Instrument (CGI). The CGI is designed to block out the intense light from host stars, enabling direct observation of exoplanets, a technology demonstration crucial for future missions aiming to image Earth-like worlds, nasa stated in a January 31, 2024, update. HIP 71618 B is an ideal target for this demonstration due to its suitable brightness, separation from its star, and faintness at Roman's operating wavelengths, providing a realistic test for these advanced imaging techniques.

• Directly imaging exoplanets presents immense challenges because host stars are millions to billions of times brighter than their orbiting planets, making the faint planetary light difficult to discern, as explained by NASA Science. Overcoming this "firefly next to a spotlight" problem requires sophisticated tools like coronagraphs and adaptive optics to suppress starlight and correct for atmospheric distortions, according to a November 12, 2025, video from Physics Frontier. The OASIS program's success in identifying these objects demonstrates significant progress in addressing these technical hurdles.

• These initial findings from the OASIS program are expected to be followed by many more discoveries, further clarifying how planets and brown dwarfs form and evolve, as reported by UT San Antonio Today. The validation of coronagraph technologies using targets like HIP 71618 B will directly contribute to the Roman Space Telescope's ability to search for and characterize potentially habitable Earth-like planets, pushing the boundaries of humanity's quest to understand our place in the universe.