Imagine peering into the vast darkness of space and spotting not just stars, but the faint glow of hidden worlds orbiting them. This is exactly what a team of astronomers has achieved, using cutting-edge technology to uncover two remarkable celestial bodies around distant stars. But here's where it gets even more fascinating: these discoveries are just the beginning of a groundbreaking survey that could revolutionize our understanding of how planets and brown dwarfs form and evolve.
An international team of astronomers has announced the detection of two extraordinary substellar companions—one a gas giant planet and the other a brown dwarf—orbiting stars far beyond our solar system. This feat was made possible by the Subaru Telescope’s advanced adaptive-optics imaging system, SCExAO, combined with precise stellar measurements from the European Space Agency’s Hipparcos and Gaia missions. These findings mark the first results from the OASIS (Observing Accelerators with SCExAO Imaging Survey) program, which aims to locate and study massive planets and brown dwarfs in ways we’ve never done before.
But here’s the challenge: Only about 1% of stars host these massive objects, and even when they’re young and glowing brightly from their formation, they’re still incredibly faint compared to their host stars. It’s like trying to spot a firefly next to a searchlight. So, where do you even begin looking? OASIS tackles this problem head-on. By analyzing data from Hipparcos and Gaia, the program identifies stars whose motion suggests they’re being gravitationally influenced by unseen companions. These stars are then targeted with SCExAO, which provides the precision needed to capture images of these elusive objects.
And this is the part most people miss: OASIS isn’t just finding these objects—it’s also measuring their masses and tracking their orbits around stars we never thought to examine. As Thayne Currie, the OASIS Principal Investigator at The University of Texas at San Antonio (UTSA), explains, “With OASIS, we are able to find, weigh, and track the orbits of massive planets and brown dwarfs around stars we never thought of looking at before.”
The first discovery, HIP 54515 b, is a gas giant with a mass nearly 18 times that of Jupiter, orbiting a star twice as massive as our Sun. Located about 275 light-years away, this planet orbits its star at a distance similar to Neptune’s orbit around the Sun. Despite its size, HIP 54515 b appears incredibly close to its star in the sky, making its detection a testament to the power of SCExAO. As Currie notes, “HIP 54515 b was imaged about 0.15 arc-seconds from its star—roughly the size of a baseball seen from 100 kilometers away. This required the sharpest images possible, enabled by Maunakea’s exceptional observing conditions and SCExAO’s advanced technology.”
Interestingly, HIP 54515 b joins a growing trend of superjovian planets with slightly elliptical orbits, hinting at formation histories different from those of gas giants in our Solar System. Could this mean these planets formed under unique conditions? It’s a question that sparks debate among astronomers.
The second discovery, HIP 71618 B, is a brown dwarf orbiting a similarly massive star. With a mass 60 times that of Jupiter, it follows a highly elongated, elliptical orbit around its star. While not a planet, HIP 71618 B is particularly significant because it meets the strict criteria for the Roman Space Telescope’s Coronagraph Instrument technology demonstration, planned for 2027. This experiment aims to test advanced imaging technologies that could one day reveal Earth-like planets orbiting other stars by suppressing the glare of their host stars. Until this discovery, no system in the peer-reviewed literature met these requirements, making HIP 71618 B a game-changer for future exoplanet searches.
These discoveries highlight the power of combining space-based astrometry with ground-based direct imaging to uncover hidden worlds. OASIS continues to survey dozens of candidate systems, with more revelations expected in the coming years. These findings will not only deepen our understanding of planetary and brown dwarf formation but also pave the way for technologies to detect habitable, Earth-like worlds.
But here’s a thought-provoking question: As we push the boundaries of what we can observe, are we getting closer to answering the age-old question of whether we’re alone in the universe? And what other secrets might these newly discovered worlds hold? Share your thoughts in the comments below!
As Dr. Masayuki Kuzuhara, co-leader of OASIS, puts it, “Thanks to innovative instruments like SCExAO and Maunakea’s world-leading observing conditions, Subaru Telescope will remain a preeminent observatory, making breakthrough discoveries far into the future.”
These results were published in the Astronomical Journal and Astrophysical Journal Letters on December 3, 2025, by Currie & Li et al. and El Morsy et al., respectively. OASIS is an international collaboration supported by the National Science Foundation, NASA, and JSPS KAKENHI, involving astronomers from the United States, Japan, Canada, Chile, and Europe.
About the Subaru Telescope: Operated by the National Astronomical Observatory of Japan, the Subaru Telescope is a large optical-infrared telescope supported by the MEXT Project to Promote Large Scientific Frontiers. We are deeply grateful for the opportunity to observe the universe from Maunakea, a site of immense cultural, historical, and natural significance in Hawai`i.
