Herschel, sent in 2009 to over a million km from the Earth, has observed, over a period of more than three years, the birth of stars and the dynamics of matter in the Universe, and has enabled a comparative study of neighbouring and distant galaxies to be made. The mission will end on April 29th 2013.
The data which has been obtained to date will take many years to analyze ; nevertheless, new results were already presented at the conference which was held at ESTEC (ESA’s space research and technology centre at Noordwijk, in Holland).
A number of these results involve directly scientists from the Paris Observatory. Here are some of them :
- Herschel reveals that there are major differences between Uranus and Neptune
Since they have almost the same mass, Uranus and Neptune are often thought of as twin planets. However, we believe that that there are significant differences between them, both from the point of view of atmospheric dynamics and internal structure. Herschel has shown that there are important differences between their chemical compositions ; in particular, methane and carbon monoxide seem to be much more abundant on Neptune than on Uranus. The large abundance of CO in Neptune’s low atmosphere, which would imply that the planet has an extraordinary amount of oxygen, is truly enigmatic.
Presentation of these new results by Emmanuel Lellouch (Paris Observatory /LESIA), on 15.10.2013.
- First deep survey of the Milky Way, by Herschel
The HIFI spectrometer on the Herschel satellite has mapped with unprecedented accuracy the distribution of the diffuse interstellar gas in the Milky Way. The various clouds which are on the line of sight could be distinguished from each other using the Doppler effect, since they have different velocities ("tachygraphy"), and their properties (size, temperature, density, molecular fraction) were determined very accurately. The coldest gaz occupies a very small fraction of the volume (on the order of 5%), but constitutes most of the mass. Its gradual condensation determines star formation in our galaxy.
Presentation of these results by Maryvonne Gérin (Paris Observatory / CNRS / LERMA), on 15.10.2013.
- A fresh view of interstellar chemistry
The conditions which reign in the interstellar medium would seem at first sight to be hostile to the survival of molecules : the very low mean temperature (-200°C) should suppress many chemical reactions ; the ultraviolet radiation emitted by neighbouring stars should destroy the rare molecules which manage to to appear... Measurements made by the HIFI instrument have helped solve the 70 year old enigma of how the chemical richness of this medium came about : in fact, turbulent motions produce intermittent blasts of heat which help switch on the reactions and recreate continuously the stock of molecules, in spite of their destruction of the UV photons. This discovery reveals a hitherto hidden facette of the diffuse, heterogenous and out-of-equilibrium interstellar medium.
Concerning this news item, read also : http://sciencesetavenir.nouvelobs.com/espace/20131031.OBS3513/tornades-interstellaires-des-usines-a-molecules.html
Presentation of these new results by Benjamin Godard (LUTH) and Edith Falgarone (Paris Observatory / CNRS / LERMA),on 16.10.2013