LHS 1903 System | 16 Feb 2026

Source: TH 

Astronomers utilizing the European Space Agency’s Cheops Space Telescope have discovered a unique four-planet system orbiting the red dwarf LHS 1903, featuring a planetary arrangement that challenges current planet formation theories. 

• System Overview: The system consists of four planets - two Super-Earths (rocky) and two mini-Neptunes (gaseous) orbiting a red dwarf star located 117 light-years from Earth. 
• The Formation Paradox: Conventional models suggest rocky planets form near the star, while gas giants form farther away. 
  • However, the outermost (fourth) planet of LHS 1903 is rocky, despite being positioned beyond its gaseous siblings. 
  • Researchers suggest the planets formed one after another, depleting the available gas before the fourth planet formed, or that the fourth planet lost its atmosphere in a catastrophic event, leaving behind a rocky outer planet. 
• Rocky planets: The rocky planets are classified as Super-Earths, possessing a composition similar to Earth but with a mass two to ten times greater. 
• Sub-Neptunian Neighbors: The two middle planets are mini-Neptunes, which are larger than Earth but smaller than Neptune, characterized by thick gaseous envelopes. 
• Habitability Potential: The fourth planet is of particular scientific interest due to its estimated surface temperature of 60°C, placing it within a range that could potentially support habitability. 
• Star Characteristics: The host star, LHS 1903, is a red dwarf with only 50% of the Sun's mass and 5% of its luminosity, representing the most common type of star in the Milky Way.