Herschel telescope tracks water in our near universe

After more than thirty months of operation of the European Herschel satellite, the conference “From atoms to pebbles: Herschel’s view of Star and Planet formation”, jointly organized by CNES and IPAG (CNRS/University Grenoble 1) from 20 to 23 March in Grenoble, reviewed the mission’s contributions to our knowledge of the mechanisms of formation of planetary systems. A major discovery is the omnipresence of water in star and planet formation zones, all pointing to a spatial origin of water on our Earth.

Launched on 14 May 2009 by Ariane 5, the Herschel satellite of the ESA (European Space Agency) is the largest space telescope dedicated to astronomy in the infrared and sub-millimetre spectral range.

After more than 30 months of operation in space, more than 1.5 million kilometers from Earth, CNES, the French space agency, and the Grenoble Institute of Planetology and Astrophysics (IPAG, CNRS/University Grenoble 1) organized a symposium from March 20 to 23 that brought together more than 200 researchers from around the world, experts in star formation and planetary systems.

Among all the research papers presented at the symposium, one observation was in the spotlight: that of water.

Indeed, never before the Herschel satellite had it been possible to observe water in the Universe in such detail, particularly in gaseous form.

Four international research programmes (WISH, CHESS, HSSO and GASPS1), with the strong involvement of French laboratories² have been able to trace and measure the abundance of water and its evolution, from the birth of stars to that of the planets.

For the first time, water was thus detected in prestellar cores, but also in large quantities in protoplanetary disks, and even in young extrasolar planetary systems, in the form of gigantic reservoirs of icy comets. Moreover, these observations have led to a better understanding of the formation of water around young stars, and to a better understanding of the mechanisms of formation of stars similar to our sun or much more massive than it. In addition to acting as a natural cooler, water is a formidable probe of the movement of gas around forming stars.

In addition, a new measure of water abundance, and its variant heavy water, has revived the hypothesis that water is brought to Earth by cometary means.

These observations were made with the three instruments on board: HIFI, a high-resolution spectrometer dedicated to the study of the chemistry of the Universe, PACS and SPIRE spectro-imagers designed to map the infrared emission of dust grains.

Water is thus present throughout the cosmos, in the form of ice or gas. And it’s even the third most abundant species in the Universe. These observations help answer questions that astrophysicists and the general public alike are asking: is there water in the cosmos? Is there water in the solar system outside the Earth? Where does the water on Earth come from? Could it have been there when our planet was formed?

In addition to understanding the mechanisms of water formation around young stars, Herschel’s observations provide a vast panorama of all stellar and planetary formation regions, both from the point of view of visualizing these spaces and understanding the physical mechanisms that govern them: from the filaments structuring molecular clouds to the interactions of dust grains with the planets, to the formation of solar-type or much more massive stars. It is therefore a whole area of astrophysics that will be nourished for many years to come by exploiting the data acquired by Herschel, until the end of operations in early 2013.

The CNES has participated in the financing of the instruments and ensures the follow-up and financing of the French participations committed by the CEA, the CNRS, and many French universities and laboratories.

Notes

1 : WISH : Water In Star-forming regions with Herschel, CHESS : Chemical Herschel Surveys of Star-forming regions, HSSO : Herschel Solar System Observations, GASPS: GAS in Protoplanetary Systems

2 : En particulier le Laboratoire d’astrophysique de Bordeaux (CNRS/Université Bordeaux 1), l’Institut de recherche en astrophysique et planétologie de Toulouse (CNRS/Université Toulouse 3), l’Institut de planétologie et d’astrophysique de Grenoble (CNRS/Université de Grenoble 1), le Laboratoire d’études spatiales et d’instrumentation en astrophysique de Paris (CNRS/Observatoire de Paris/UPMC/Université Paris 7)LAB : Laboratoire d’Astrophysique de Bordeaux – IPAG : Institut de Planétologie et d’Astrophysique de Grenoble – IRAP : Institut de Recherche en Astrophysique et Planétologie de Toulouse, LESIA: Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique de Paris

L’implication de l’Institut de recherche en astrophysique et planétologie de Toulouse
Etude de l’eau dans une région de formation stellaire: origine des océans terrestres.L’eau lourde, ou oxyde de deutérium (D2O), est chimiquement similaire à l’eau (H2O). Grâce à des observations réalisées avec le satellite Herschel, il a été possible de détecter cette forme particulière d’eau, en même temps qu’un grand nombre de transitions d’eau semi-lourde (HDO), dans le nuage moléculaire Rho Ophiuchus de notre Galaxie où une étoile ressemblant à notre Soleil est en cours de fabrication. Ces éléments, combinés aux observations de l’eau sont d’excellents outils de diagnostic physico-chimique et apportent des informations sur les mécanismes de la formation stellaire à travers leur production dans un réseau chimique complexe à l’origine de la Vie telle qu’elle est connue sur la Terre.
IRAP Contacts
Charlotte Vastel – IRAP – Charlotte.Vastel@irap.omp.eu, tél : 05 61 55 75 44
Audrey Coutens – IRAP – Audrey.Coutens@irap.omp.eu, tél : 05 61 55 66 95

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