Astronomers discover ‘unique inside-out’ planetary system

Astronomers have discovered a peculiar planetary system that could reshape current theories of planet formation, after spotting a rocky planet orbiting beyond two gas giants around a distant red dwarf star.

The system, detected using the European Space Agency’s Cheops space telescope, lies about 117 light-years away in the direction of the Lynx constellation. It contains four planets—two rocky worlds and two gaseous ones—circling a small, dim red dwarf star known as LHS 1903.

What Makes the Discovery Unusual

Scientists were surprised by the planetary arrangement:

• The innermost planet is rocky.
• The next two planets are gaseous.
• The outermost planet—expected to be gaseous—turned out to be rocky.

Current models suggest that rocky planets form close to stars where heat drives away gas, while gas giants form farther out in colder regions rich in gas and ice. This system appears to break that rule.

Why It Matters

Researchers believe the outer rocky planet may have formed after much of the planet-forming material was already used up, or it migrated into its present orbit later. Either scenario challenges existing models of how planetary systems evolve.

For comparison, in our own solar system the four inner planets—Mercury, Venus, Earth, and Mars—are rocky, while the outer planets are gas-rich giants.

Bigger Picture

Since the 1990s, astronomers have discovered more than 6,100 exoplanets, revealing that planetary systems are far more diverse than once imagined. Findings like this suggest scientists may need to refine theories about how planets form and migrate around their stars.

The study was published in journal Science.

Source: Live SCIENCE