Four Planets Solved a 20-Year Mystery About Planet Formation

Four planets around one star just solved a 20-year mystery in exoplanet science.

THE RADIUS VALLEY MYSTERY

When we measure thousands of exoplanets, we see a weird pattern: planets split into TWO groups separated by a gap at 1.6-1.8 Earth radii.

Below the gap → Rocky super-Earths
Above the gap → Gassy sub-Neptunes

But WHY does this gap exist?

TWO COMPETING THEORIES

THEORY 1: Atmospheres get STRIPPED by stellar heat (close planets lose gas, far planets keep it)

THEORY 2: Planets form WITHOUT gas (disk runs out of gas during formation)

Both predict the gap. But they predict OPPOSITE patterns.

🔭 THE DISCOVERY: LHS 1903

Red dwarf star, 158 light-years away. Four planets discovered:

Planet b (2.2 days) → 1.38 R⊕, ROCKY, 6.8 g/cm³
Planet c (6.2 days) → 2.05 R⊕, GASSY, 2.9 g/cm³
Planet d (12.6 days) → 2.50 R⊕, GASSY, 2.1 g/cm³
Planet e (29.3 days) → 1.73 R⊕, ROCKY, 6.1 g/cm³

THE SMOKING GUN

Planet e is the FARTHEST from the star (coldest, 333K).

If atmospheres were stripped by heat → Planet e should be GASSY
If planets formed without gas → Planet e CAN be ROCKY

Result? Planet e is ROCKY with NO atmosphere.

This is the first system with planets on BOTH sides of the radius valley. And the pattern proves gas-depleted formation occurred in this system.

One star. Four planets. Mystery solved.

📄 Published in Science, Feb 12, 2026
DOI: 10.1126/science.adl2348

Data: TESS (discovery) + CHEOPS (follow-up) + HARPS-N (masses)

I'm Nerduino - PhD in astronomy, 10 years at NASA JPL working on the Planck mission. I break down cutting-edge space science.

🔔 Subscribe for more exoplanet discoveries!

#Exoplanets #RadiusValley #PlanetFormation #LHS1903 #Astronomy #Space #Science #TESS #CHEOPS #NASA #Astrophysics #SpaceDiscovery
```

Видео Four Planets Solved a 20-Year Mystery About Planet Formation канала Nerduino