Using the Mid-InfraRed (MIRI) instrument aboard the Webb Space Telescope, astronomers have detected hot water vapor in the inner part of the disk of gas and dust around the young star PDS 70. Thus, any rocky planets in this part of the disk could benefit from an important local water reservoir and be supplied with water during their formation (natureJuly 24).
With an estimated age of 5.4 million years, PDS 70 is the first relatively ancient disk in which astronomers have discovered water. The gas and dust content of the planet-forming disks decreases over time. Dust and gas surrounding a star are expelled by radiation or winds from the central star or gather together into larger fragments that eventually form planets. Since there was no water in previous studies of similar disks, astronomers suspected that water in the central part of a planet-forming disk could not withstand the star’s intense radiation, leading to a very dry environment where rocky planets form.
MIRI observations show that the central parts of the old, dust-poor disks aren’t so dry after all. And if this is true, then many of the terrestrial planets that form in these regions could be born with an essential ingredient for sustaining life.
It should be noted that no planets have been discovered in the central part of the disk around PDS-70 yet. However, astronomers beyond that have two so-called Gas giants Discover: PDS 70 b and c. These planets accumulated dust and gas around them as they orbited their parent star, creating a wide ring hole in the disk where almost no matter could be found.
Since the presence of water was somewhat unexpected, scientists are now exploring different scenarios to explain their discovery. One possibility is that the water is the remnant of the water haze that preceded the disc stage. Another source could be gas ingress from the outer parts of the PDS 70 disc. Under certain conditions, oxygen and hydrogen gas can combine there to form water vapor. This vapor can then be trapped by icy dust particles migrating from the outer dust ring. The central star is still too dim to vaporize the water ice in the outer parts of the disk. Only when the dust particles get close to the star does the ice they carry with them turn into gas. (EE)
Water detected in the rocky planet formation region provides evidence of habitability
