GJ 523 b Archives

“Mega-Earths” Are Likely An Artifact Of Stellar Activity

by Keith CowingOctober 14, 2026October 14, 2026

[astro-ph.EP]. Empirical relations and planet formation simulations suggest an upper mass limit for rocky planets of ∼10M⊕, as cores above this will almost certainly undergo runaway gas accretion.

Radius-density diagram of confirmed exoplanets from the NASA Exoplanet Archive with radii below 5 R⊕ and mass and radius measurements significant at better than 4σ. The best-fit Gaussian mixture model, described in Section 6, is shown by the purple contours and has been rescaled for visibility. The model approximately recovers the loci of super-Earths (tan), sub-Neptunes (green), and Neptune-like planets (blue). A fourth component contains planets that do not belong to those main groups, including the mega-Earths (red), such as GJ 523b, and other high-density outliers (black). The observational mega-Earth class is indicated by the red arrows (Rp ≥ 2.1 R⊕, ρp ≥ 5.5 g cm−3). -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

GJ 523b Is A Massive, 170 Myr-old Mega-Earth, Likely On A Polar Orbit

by Keith CowingMarch 29, 2026March 29, 2026

We use WIYN/NEID radial velocity measurements to confirm the planetary nature and measure the mass of the TESS transiting exoplanet candidate around the mid-K dwarf GJ 523 (V=9.23, K=6.525).