Particle.news

Download on the App Store

Giant Exoplanet Circling Tiny Red Dwarf Challenges Formation Theories

JWST’s upcoming study of its methane-dominated atmosphere could reveal how such a massive world emerged around a star one-fifth the Sun’s mass.

Image
An artist's illustration of an exoplanet and its star

Overview

  • TOI-6894b is a low-density gas giant with a radius just above Saturn’s and roughly half its mass, orbiting at a temperature near 420 K.
  • The host star, TOI-6894, is only 20 percent the Sun’s mass, making it the smallest known star to carry a transiting giant planet.
  • Astronomers spotted TOI-6894b in TESS data among over 91,000 low-mass red dwarfs and confirmed it with ESO’s Very Large Telescope, publishing the finding in Nature Astronomy on June 4, 2025.
  • The planet’s existence undermines standard core accretion theory and points toward alternative formation processes such as gravitational instability.
  • Within the next year, the James Webb Space Telescope will observe TOI-6894b’s atmosphere to detect methane and ammonia that can distinguish between rival formation models and reassess the prevalence of giant planets in the galaxy.