NASA’s James Webb Space Telescope scientists have made an important discovery about how planets form. By observing water vapor in “protoplanetary disks”, the disks of dust and gas that swirl around young stars, Webb has confirmed a physical process key to planet formation.

Scientists have long thought that small icy pebbles that form in the cold outer parts of protoplanetary disks, similar to where comets come from in our solar system, are important for building planets.

The theories say these pebble seeds should slowly drift inward through the gaseous disk due to friction. This inward movement provides solid material and water to developing planets closer to the star.

An important prediction is that when icy pebbles cross the “snow line” – where it’s warm enough for ice to turn to vapor – they should release a lot of cold water vapor. This is exactly what Webb saw in two compact protoplanetary disks!

The researchers used Webb’s MIRI instrument, which is good at detecting water, to look at four disks around stars like our Sun.

Two disks were compact without gaps, while two had spreading rings. They expected more efficient inward pebble drifting and extra inner water for the compact disks.

Webb’s powerful observations clearly showed excess cold water in the compact disks inside the snow line, right where planet seeds are forming. This confirms that icy pebbles bring water from the outer to inner disk regions during planet formation.

Before, scientists thought planet-forming regions didn’t interact much. Now we see icy pebbles drifting long distances, just like what probably happened to bring water to Earth.

Jupiter may have blocked drifting pebbles from reaching our inner planets, keeping them drier.

Webb’s amazing images give us the clearest view yet of how water and rocky planets form together in swirly disks around young stars. Its discoveries will help reveal more secrets of planetary nurseries across the galaxy.


NASA | Andrea Banzatti, Klaus M. Pontoppidan, et al., JWST Reveals Excess Cool Water near the Snow Line in Compact Disks, Consistent with Pebble Drift. The Astrophysical Journal Letters, vol.957, no.2. DOI 10.3847/2041-8213/acf5ec

  • Share this article:

Discover more from LBV Magazine English Edition

Subscribe to get the latest posts sent to your email.

Something went wrong. Please refresh the page and/or try again.