In the summer of 2008, two of the most sensitive space observatories ever launched will lift off from Kourou in French Guiana. On board the Ariane 5 rocket will be Herschel, the world’s most powerful heat-seeking space telescope, and Planck, which will study the faint radiation that filled the Universe immediately after the Big Bang.
Everything about ESA’s Herschel Space Observatory is big. The satellite is about 7 metres high and 4.3 metres wide, with a mass of 3.25 tonnes. Its telescope has a main mirror that measures 3.5 metres across, the largest ever to be built for a scientific spacecraft.
The observatory is named after another scientific giant, the German astronomer and musician William Herschel. In 1800, Herschel was using a glass prism to split white light into a rainbow of colours. To his surprise, a thermometer placed alongside the red light beam showed a rise in temperature. Herschel had discovered the invisible light from the Sun that scientists know as “infrared radiation”. We often just call it “heat”.
Herschel will be located 1.5 million kilometres away, far enough to avoid problems caused by infrared radiation from the Earth interfering with observations. Its three instruments will be cooled by liquid helium so that they are close to absolute zero (-273°C).
Herschel will be used to study the ‘cold’ Universe. Its supercool ‘eyes’ will see though dust clouds to study star forming regions, galactic centres and hidden planets. Above all, it will seek to find out how galaxies and stars formed in the early Universe.
