GJ 523b discovery challenges planetary formation theories

Astronomers have discovered a unique exoplanet, informally dubbed GJ 523b or a ‘Mega-Earth’, which challenges existing models of planetary formation. Located approximately 87 light-years away, the planet orbits a mid-K dwarf star every 17.75 days.

Data from NASA’s TESS mission and the WIYN Telescope reveal that GJ 523b has a radius roughly 2.55 times that of Earth, yet its mass is approximately 23.5 times greater. This high density suggests a predominantly rocky composition. Under current scientific theories, a planet of this mass should have accumulated a massive hydrogen and helium atmosphere to become a gas giant, similar to Jupiter or Saturn.

Researchers from the University of Wisconsin-Madison, including graduate student Max Kroft, are investigating why this planet remained rocky. Potential explanations include the stripping of its atmosphere due to high stellar radiation or a massive collision between two protoplanets during its early stages. The system is estimated to be relatively young, at approximately 170 million years old.