Exoplanet GJ 523b discovered with unusual mass and orbit

Astronomers have discovered a massive exoplanet, GJ 523b, that challenges existing models of planetary formation. The rocky exoplanet possesses a mass approximately 23 times that of Earth, yet its radius is only 2.5 times larger, making it roughly 50% denser than Earth.

This discovery is significant because a planet with such high mass and a large rocky or metallic core would typically have enough gravitational pull to retain a thick layer of hydrogen gas during its formation, categorizing it as a sub-Neptune. However, GJ 523b lacks a significant atmosphere. Additionally, the star system is relatively young, having formed only about 170 million years ago, which makes the loss of hydrogen difficult to explain through thermal effects alone.

The planet also exhibits an unusual orbital path. Instead of orbiting on the equatorial plane of its host star like most planets, GJ 523b moves on an orbit that passes near the star's poles. Researchers suggest this extreme inclination could be the result of gravitational influence from a larger, as-yet-undiscovered sibling planet within the system.