Astronomers Find 23.5-Earth-Mass Gliese 523b on Likely Polar Orbit

3 articles · Updated · Sci.News · Aug 22

Gliese 523b emerged as a rare “mega-Earth” after U.S. astronomers confirmed a planet 2.55 times Earth’s radius but 23.5 times its mass, making it unusually dense for its size.
NEID radial-velocity measurements combined with earlier TESS transit data pinned down the world’s mass, size and 17.75-day orbit around Gliese 523, a mid-K dwarf 87 light-years away.
Ages inferred from Gliese 523 and companion stars put the system at about 169 million years old, while the planet’s orbit appears tilted by at least 71 degrees to the star’s equator.
That mix of youth, high density, scant atmosphere and steep misalignment strains standard formation models, pointing to possibilities such as giant impacts, atmospheric stripping or perturbations from an unseen outer companion.