A dataset provided by the European Space Agency

Name OT2_mhogerhe_2
Title A deep HIFI search for cold para-water vapor in three protoplanetary disks


DOI 10.5270/esa-eckew4k
Author hogerheijde, m.
Description Using the HIFI spectrometer on the Herschel Space Observatory we have detected the ground state lines of cold water vapor in the outer reaches of the disk around the nearby young star TW Hya. Only UV-induced photodesorption of water molecules off icy grains can explain the presence of water vapor in these cold regions. The lines of ortho-H2O 110-101 and para-H2O 111-000 are weaker than expected, suggesting that up to 80% of the larger, icy grains have settled out of the ultraviolet.s reach toward the midplane, representing a .hidden. reservoir of thousands of Earth Oceans. Analysis of the line strengths revealed a water ortho-to-para ratio of 0.77, much lower than found in Solar System comets (1.5-3), leading us to suggest that comets consist of ice mixtures from across the full extent of the Solar Nebula and implying long-range mixing of icy material in disks. We have been awarded 47 hrs in Herschel OT1 to search three more gas-rich protoplanetary disks for the presence of ortho-H2O 110-101 at 557 GHz with HIFI (DM Tau, HD100546, and AA Tau). These targets represent, after TW Hya, the closest, mostly likely candidates to detect these weak lines. For OT2 we propose an equally deep search for the para-H2O 111-000 line at 1113 GHz to these same three targets. These proposed observations form a unique legacy of Herschel and HIFI: together with our OT1 data, they will provide a complete inventory of cold water in these disks; they will allow us to investigate if low ortho-to-para ratios are common in protoplanetary disks or unique to TW Hya; and they will provide unparalleled insight into the origin of the Earth.s oceans and the possibility of ocean-covered worlds elsewhere.
Instrument HIFI_HifiPoint_dbs
Temporal Coverage 2012-07-24T17:42:46Z/2013-02-26T23:59:13Z
Version SPG v14.1.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 ┬Ám range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/herschel/
Date Published 2013-08-26T18:22:36Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2013-08-26T18:22:36Z, OT2_mhogerhe_2, SPG v14.1.0. https://doi.org/10.5270/esa-eckew4k