Astronomers have discovered a remarkable rocky exoplanet called GJ 523b that challenges our understanding of planetary formation. The planet is 23 times more massive than Earth but only 2.5 times wider, making it one of the densest rocky worlds ever observed.
The discovery, published in a new study, identifies GJ 523b as a "mega-Earth" — a category of planet that sits between super-Earths and mini-Neptunes in terms of mass and composition. At nearly 170 million years old, the planet is relatively young in astronomical terms.
What makes GJ 523b particularly intriguing is its density. While it packs 23 times Earth's mass into a body only 2.5 times our planet's width, this suggests an extremely dense interior, likely composed primarily of heavy elements and rock rather than the gaseous envelopes found on larger planets.
The study also found that GJ 523b likely orbits its host star in a polar trajectory — meaning it passes over the star's poles rather than orbiting around its equator. This unusual orbital configuration could provide clues about the violent gravitational interactions that shaped the planet's early history.
The discovery adds to the growing catalog of exotic planetary types that astronomers have found beyond our solar system, expanding our understanding of the diverse ways planets can form and evolve.
