Vol. 535
In section 4. Extragalactic astronomy

Molecules at z=0.89: A 4-mm-rest-frame absorption-line survey toward PKS1830-211

Gravitational lensing gives rise to a number of surprising phenomena, and one of these is the possibility of observing molecular absorption lines towards normal molecular clouds in normal spiral galaxies at high red shift. This possibility is exploited by Muller et al. in the 7mm (or 4mm in the rest frame) survey of molecular lines using the Australia Telescope Compact Array. The authors use this data both to measure the cosmic microwave background temperature at this red shift, as well as putting limits on the variations in fundamental constants. They additionally measure molecular abundances remarkably close to those found in the Milky Way.