A stellar system has just revealed a planet with unprecedented characteristics. Its right-angle orbit around two stars is a first.
Configuration of 2M1510 and naming convention for the different bodies.
The brown dwarfs are in red and the planet in blue. The direction of Earth relative to the binary is indicated.
This discovery, made using the ESO's Very Large Telescope, involves a planet orbiting a pair of brown dwarfs. Unlike known exoplanets to date, this one follows a polar trajectory, perpendicular to the orbital plane of the stars.
These brown dwarfs, intermediate objects between giant planets and stars, form a rare binary system. The exoplanet, named 2M1510 (AB) b, was detected through the gravitational disturbances it induces on their orbits. This indirect method confirmed its presence and unusual orbit.
The international team, led by Thomas Baycroft from the University of Birmingham, published their findings in
Science Advances. Their study highlights the importance of this discovery for understanding the diversity of planetary systems. Brown dwarfs, less luminous than stars, provide an unusual environment for planet formation.
This serendipitous discovery opens new perspectives on planet formation. Binary systems, already known to host planets, reveal an extreme configuration here. Researchers now plan to search for other exoplanets with similar orbits, which could uncover previously unknown formation mechanisms. Future observations will target other binary systems to determine whether this configuration is unique or widespread.
Animation showing the polar orbit of the exoplanet around the two brown dwarfs.
Credit: ESO What is a polar orbit?
A polar orbit is a trajectory where an object, such as a planet, revolves around another by passing over its poles. Unlike equatorial orbits, which follow the plane of the central object's equator, polar orbits are perpendicular to this plane.
In the case of exoplanet 2M1510 (AB) b, this configuration is particularly rare because it involves two stars. The planet does not orbit in the same plane as the stars but at a right angle.
This discovery suggests that planetary formation mechanisms can result in highly diverse orbital configurations. Theoretical models will now need to incorporate this possibility, which could lead to a better understanding of the dynamics of multiple systems.
Why are brown dwarfs special?
Brown dwarfs occupy an intermediate position between gas giant planets and stars. Too massive to be planets, they lack sufficient mass to initiate hydrogen nuclear fusion, a characteristic of stars.
Their low luminosity and relatively cool temperatures make them difficult to study. Yet, they play a key role in understanding the formation of stellar and planetary systems.
The discovery of a planet in a polar orbit around a pair of brown dwarfs shows that these objects can host planets.