Searching for Life in the Solar System ... And Beyond

A Research Discussion Meeting
London, UK - 31 October 1996


E Chassefiere (LMD/CNRS, France), A Coustenis, R Wittenberg, J Schneider (Obs. de Meudon, France), A Penny (Rutherford Appleton Lab, UK) T Greene (IFA, US)

We have observed 51 Peg with UKIRT and IRTF, seeking to detect absorption lines from the material evaporated from its Jupiter-mass companion by the stellar wind from 51 Peg. Observations were taken on Aug. 18, 19, 27, 29, Sep. 3 and 4, 1996 - nights when the planet was either at quadratures or at transit.

As the companion's orbital plane is thought to be near the line-of-sight, there is some chance that an extended atmosphere would occult the star. This in turn may be detected by comparing the infrared spectrum of the star at on-transit and off-transit times.

Hydrodynamic equations have been solved in the collisional inner part of the corona, whereas the Jeans formulation is used in the exosphere. Enhanced EUV flux conditions have been considered. It has been shown that a large EUV flux may yield the formation of an extended collisional corona of size typically 10 planetary radii.

Due to the bombardment of the fluid corona by stellar wind protons, very high temperatures are expected to prevail in the outer regions of the corona (up to 1 million degrees), and high values of the hydrogen escape flux may be reached (although it is not guaranteed that photochemistry can supply the flow at the required level).

The reduction of the observations is currently under way and this poster given preliminary results.