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Register a new userDetection of the Water Reservoir in a Forming Planetary System
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Added by
Michiel R. Hogerheijde
Publication date
2011
fields
Physics
and research's language is
English
Authors
Michiel R. Hogerheijde
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Icy bodies may have delivered the oceans to the early Earth, yet little is known about water in the ice-dominated regions of extra-solar planet-forming disks. The Heterodyne Instrument for the Far-Infrared on-board the Herschel Space Observatory has detected emission from both spin isomers of cold water vapor from the disk around the young star TW Hydrae. This water vapor likely originates from ice-coated solids near the disk surface hinting at a water ice reservoir equivalent to several thousand Earth Oceans in mass. The waters ortho-to-para ratio falls well below that of Solar System comets, suggesting that comets contain heterogeneous ice mixtures collected across the entire solar nebula during the early stages of planetary birth.
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We report on the detection of a rich water reservoir in the protostellar envelope of the Class 0 source HH211. In striking contrast to all other molecules detected with Herschel/PACS, water emission peaks around the central source where both ortho and para forms are detected. The measured ortho-to-para ratio of just 0.65 indicates formation of water-ice at very low temperatures and a non-destructive photo-desorption process around the protostar. While part of the water emission is likely related to collisional excitation, the centralized morphology around the protostar suggests that radiative excitation is also significant, despite the fact that radiation appears to have a very different impact on the water molecules when compared to the terminal outflow shocks. The very low ortho-to-para ratio suggests that water around the protostar originates from primordial envelope material that has never been thermally processed before.
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