🌟 A brown dwarf and a giant exoplanet observed directly with unprecedented precision

Currently, only about 1% of stars host giant planets or brown dwarfs that our telescopes can photograph directly. This scarcity raises a question: how can we uncover these so discreet objects, drowned in the dazzling light of their host stars? A team of astronomers has just made a breakthrough by using an ingenious method that combines space-based measurements and cutting-edge imaging from the Subaru Telescope.

Two new discreet objects have thus been directly identified, one being a giant planet and the other a brown dwarf. These discoveries are the first from the OASIS program, which aims to spot hidden objects by analyzing stellar motions. According to the study published in The Astronomical Journal, this approach allows for precisely targeting stars whose trajectory is perturbed by the gravity of an invisible companion, before observing them with adaptive instruments.


The planet, named HIP 54515 b, is located 271 light-years away in the constellation Leo. With a mass close to 18 times that of Jupiter, it orbits its star at a distance comparable to that of Neptune from the Sun. Its detection was made possible thanks to the SCExAO system on the Subaru Telescope, which produces extremely sharp images by correcting atmospheric turbulence (see below), allowing the object to be distinguished despite its apparent proximity to the star.

The second object, HIP 71618 B, is a brown dwarf (see below) located 169 light-years away in the constellation Boötes. With a mass equivalent to 60 times that of Jupiter, it represents an intermediate stage between planets and stars, not possessing enough mass to trigger nuclear reactions. These characteristics make it an ideal target for future observation missions.


The brown dwarf HIP 71618 B plays a special role for NASA's future Roman space telescope. Before this discovery, no object perfectly met the strict requirements for testing Roman's coronagraphs, essential systems for imaging Earth-like planets. HIP 71618 B fills this gap, as its brightness and position are suited to the operational wavelengths, thereby validating the technologies necessary for the search for habitable exoplanets.

How Adaptive Optics Works

Adaptive optics is a key technology used in telescopes like Subaru to obtain sharp images from the ground. It corrects in real-time the distortions caused by Earth's atmosphere, which blur the light from celestial objects. Deformable mirrors adjust their surface thousands of times per second, compensating for turbulence and allowing very faint objects near stars to be distinguished.

Without this correction, direct observations of planets or brown dwarfs would be practically impossible, as their light is drowned out by that of their host star. Systems like SCExAO on Subaru exploit this technique to achieve unprecedented precision, essential for studying distant companions. This makes it possible to photograph objects that would otherwise remain hidden.

The application of adaptive optics transforms astronomy by improving image resolution, comparable to what would be obtained from space. It is used in various projects, from hunting exoplanets to studying distant galaxies. Its development continues to push the limits of observation, facilitating discoveries and paving the way for future missions.

The Nature of Brown Dwarfs

Brown dwarfs are celestial objects that lie at the boundary between giant planets and stars. They form like stars, from clouds of gas and dust, but their mass is insufficient to trigger nuclear fusion of hydrogen in their core. This prevents them from shining steadily like stars, leaving them to cool slowly over time.

With masses typically between 13 and 80 times that of Jupiter, they emit faint infrared light due to the residual heat from their formation. This property makes them detectable with sensitive instruments, but they remain much less luminous than stars. Their study helps astronomers understand stellar and planetary formation processes, as they represent a missing link in the evolution of systems.

The discovery of brown dwarfs like HIP 71618 B offers unique opportunities to test astronomical technologies. Their moderate brightness and distance from their host stars make them ideal targets for validating instruments like coronagraphs, essential for searching for Earth-like planets. Thus, they play a central role in advancing space exploration.