Water Vapor Detected in Protoplanetary Disk: James Webb Telescope Observations

JAKARTA – Astronomers have detected water vapor in the interior of a protoplanetary disk, where rocky planets may have formed for the first time, thanks to data from NASA’s James Webb Telescope.

Located 370 light years away, the planetary system, dubbed PDS 70, was discovered thanks to new measurements from the Webb Telescope’s Mid-Infrared Instrument (MIRI), which houses an inner and outer disk of gas and dust.

The two disks, separated by a gap 5 billion miles wide, and within the gap are two gas giant planets, a sign that matter is uniting to create new worlds.

They, astronomers also say, have seen water vapor in the inner disk area before the rift, where rocky terrestrial planets may have been born.

“We’ve seen water on other disks, but not as close and within systems where planets are currently clustered. We weren’t able to make measurements like this before Webb,” said lead author of the study Giulia Perotti from Max Planck Institute for Astronomy (MPIA), quoted from NASA’s official website, Monday, July 31.

PDS 70 is a K-type star, cooler than the Sun and estimated to be 5.4 million years old. This star, relatively old in terms of stars with planet-forming disks, is what made the discovery of water vapor surprising.

Over time, the gas and dust content of the planet-forming disc decreased. Either the central star’s radiation and winds blew the material away, or the dust grew into larger objects, eventually forming planets.

“This discovery is very exciting, because it investigates the region where rocky planets similar to Earth usually form,” said MPIA director Thomas Henning, co-author of the paper which has been published in the journal Nature, recently.

Because previous studies failed to detect water in a similarly aged central disk region, astronomers suspect it may not have survived the harsh radiation of stars, leading to a dry environment for the formation of any rocky planets.

Astronomers have yet to detect any planets forming within the inner disk of PDS 70. However, they do see the raw material for building rocky worlds in the form of silicates.

The water vapor detection implies that if rocky planets formed there, they would have had water available from the start. The discovery raises the question of where the water comes from.

Next, the astronomers then considered two different scenarios to explain their findings. First, water molecules form on the spot, which they detect when hydrogen and oxygen atoms combine.

Second, it could be that ice-coated dust particles are transported from the cold outer disk to the hot inner disk, where water ice sublimates and turns to steam. Such a transport system would be surprising, as the dust has to pass through the huge gap carved by the two giant planets.

Another question raised by this discovery is how water can survive so close to a star, when the star’s ultraviolet light has to break up water molecules.

Apparently, the surrounding materials such as dust and other water molecules serve as a protective shield. As a result, the water detected in the inner disk of the PDS 70 can survive destruction.

For follow-up research, astronomers will use two more Webb Telescope instruments, the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) to study the PDS 70 system in an effort to gain greater understanding.

Tags: james webb telescope astronomy

2023-07-31 20:05:00
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