What does infrared reveal about the Universe that optical light does not?
We used to summarise infrared astronomy as ‘the old, the cold, and the dirty’. The old because the cosmic expansion redshifts light from distant objects into the infrared; this is some of the oldest light in the Universe. The cold because in the infrared we can see objects which are too cool to radiate much visible light. The dirty because much of the infrared light that we see is radiated by particles of interstellar and circumstellar dust, and also because dust clouds that are opaque at visible wavelengths may be quite transparent in the infrared.
What do you think have been Spitzer’s highlights?
First would be the identification of seven Earth-sized exoplanets – at least several of which are potentially habitable – orbiting the same star some 40 lightyears from Earth. This is one example of our work on exoplanets, which has certainly been a high point of the mission. Another area of major impact has been our study of the earliest, most distant galaxies. Working in tandem with the Hubble Space Telescope, we have identified galaxies that are seen as they were when the Universe was no more than a few per cent of its current age and size. One-off results, such as the spectrum of the interior material of Comet Tempel I as revealed by the Deep Impact mission, or the discovery of C60 (interstellar buckyballs) in space have been very exciting as well.
Michael Werner is a senior research scientist at the NASA Jet Propulsion Laboratory, California Institute of Technology. He has been the lead scientist for the Spitzer Space Telescope since 1984.