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2h ago

Astronomers Find 'Inside-Out' Four-Planet System Around Red Dwarf LHS 1903

A peer-reviewed study argues the worlds formed one by one in a gas-starved disk, a testable claim that researchers say now needs atmospheric checks with the James Webb Space Telescope.

NASA's Transiting Exoplanet Survey Satellite, or TESS, was launched in 2018 to find new planets orbiting other stars.
A conceptual view of a red dwarf star, the same type as LHS 1903 and the most common type of star in the universe.
Artist impression of the planetary system around the star LHS 1903

Overview

  • From the star outward, the planets follow a rocky–gaseous–gaseous–rocky order, with the outer world LHS 1903 e about 1.7 times Earth’s radius and consistent with a rocky composition.
  • LHS 1903 lies roughly 116 light-years away; its four planets have compact orbits under 30 days and sizes spanning about 1.4 to 2.5 Earth radii.
  • NASA’s TESS first flagged the system, and ESA’s Cheops plus additional observatories refined the planets’ radii, orbits and inferred densities.
  • Dynamical simulations reported in Science disfavor scenarios such as giant impacts, atmospheric stripping or planet swapping as primary causes of the odd architecture.
  • The authors propose sequential, inside-out formation in a gas-depleted disk, and independent experts highlight the need for JWST spectroscopy to probe atmospheres and formation histories.