Astronomers have announced the first discoveries from the Observing Accelerators with SCExAO Imaging Survey (OASIS), a new program utilizing the Subaru Telescope in Hawai’i to identify massive planets and brown dwarfs orbiting distant stars. The findings, detailed in a study published in The Astronomical Journal in December 2025, include the detection of a planet, HIP 54515 b, and a brown dwarf.
HIP 54515 b orbits a star located 271 light-years away in the constellation Leo. Researchers estimate the planet has a mass nearly 18 times that of Jupiter and orbits its star at a distance comparable to Neptune’s orbit around our sun. The proximity of the system to Earth – described by astronomers as being comparable to viewing a baseball from a distance of 100 kilometers – aided in the observation.
The OASIS program addresses a significant challenge in exoplanet detection: the extreme faintness of planets and brown dwarfs compared to their host stars. Only about 1% of stars are estimated to host massive planets and brown dwarfs bright enough to be directly imaged with current telescopes. Even in young planetary systems, where these objects retain heat from their formation, they remain difficult to distinguish from stellar glare.
OASIS, led by Thayne Currie and Masayuki Kuzuhara, employs a two-step process. First, it analyzes data from the European Space Agency’s Hipparcos and Gaia missions to identify stars exhibiting subtle movements caused by the gravitational pull of unseen companions. When a star shows evidence of being “tugged” or “wobbled,” the Subaru Telescope is then directed towards that target.
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system is then used to capture high-resolution images, directly photographing these hidden objects. The system’s precision was crucial in observing HIP 54515 b despite the challenges of separating its light from the host star.
These discoveries also have implications for NASA’s upcoming Roman Space Telescope. The data gathered by OASIS will help test critical technologies for the Roman Space Telescope’s coronagraph, which is designed to directly image Earth-like planets around other stars.
Astronomers anticipate that the Subaru Telescope will continue to play a key role in astronomical discoveries as new, advanced telescopes come online.
