Title: NASA/ESA/CSA James Webb Space Telescope Detects Water Vapor in Protoplanetary System
Date: 24/07/2023
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The NASA/ESA/CSA James Webb Space Telescope’s Mid-InfraRed Instrument (MIRI) has made a groundbreaking discovery, detecting water vapor in the inner disc of the PDS 70 system, located 370 light-years away. This remarkable finding marks the first detection of water in the terrestrial region of a disc known to harbor multiple protoplanets.
Water, an essential component for life as we know it, has long mystified scientists regarding its origins and whether it exists on distant exoplanets. Clues to these questions may be revealed through the study of the PDS 70 system, which consists of an inner disc and an outer disc separated by a distance of eight billion km and known to host two gas-giant planets. MIRI’s detection of water vapor in the inner disc at distances less than 160 million km from the star suggests the potential formation of rocky, terrestrial planets, similar to Earth’s orbit around the Sun.
Lead author Giulia Perotti of the Max Planck Institute for Astronomy (MPIA) hailed the discovery as groundbreaking, explaining, “We’ve seen water in other discs, but not so close in and in a system where planets are currently assembling. We couldn’t make this type of measurement before Webb.” MPIA director Thomas Henning, also a co-author, described the finding as extremely exciting, as it probes the region where rocky planets similar to Earth typically form.
The PDS 70 system, a K-type star cooler than the Sun, is estimated to be 5.4 million years old, relatively old for stars with planet-forming discs. This makes the detection of water vapor particularly surprising since previous studies failed to detect water in similar-aged discs’ central regions. Astronomers had suspected that the harsh stellar radiation would prevent the survival of water, leading to a dry environment for rocky planet formation.
While astronomers have yet to detect any planets forming within the PDS 70 inner disc, the presence of silicates indicates the raw materials needed for rocky planet formation. The detection of water vapor implies that if rocky planets are indeed forming, they will have water available to them from the beginning.
The origin of the water detected in the PDS 70 system raises intriguing questions. The MINDS team, responsible for the research, considered two possible scenarios. The first involves water molecules forming in place, as hydrogen and oxygen atoms combine. The second possibility is the transportation of ice-coated dust particles from the cool outer disc to the hot inner disc, where the water ice sublimates and turns into vapor. However, this transport mechanism would require the dust to cross the large gap between the two giant planets, which presents a surprising challenge.
Furthermore, the discovery prompts the question of how water can survive so close to the star, where its ultraviolet light should break apart water molecules. The team suggests that surrounding materials, such as dust and other water molecules, likely act as a protective shield, allowing the water to survive.
In their continued efforts to unravel the mysteries of the PDS 70 system, the team plans to use two additional instruments on Webb, the Near-InfraRed Camera (NIRCam) and the Near-InfraRed Spectrograph (NIRSpec). These instruments will provide further insights into the composition and dynamics of the system.
The observations leading to this discovery were made as part of the Guaranteed Time Observation program 1282 and have been published in the journal Nature.
The James Webb Space Telescope, launched under an international collaboration between NASA, ESA, and the Canadian Space Agency (CSA), is the largest and most powerful telescope ever deployed in space. The European Space Agency (ESA) played a crucial role in the development, validation, and launch service of the telescope.
As scientists continue to unravel the mysteries of the universe, this discovery brings us closer to understanding the origin of water and the potential for habitable planets beyond our solar system.
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