Herschel will reveal the young universe in new detail (Image: ESA)



Video: See animations of the telescope and launch Video: See animations of the telescope and launch

FROM an astronomer’s perspective, the universe is a pretty cool place. In fact it’s positively chilly, with more than half the energy emitted by normal matter coming from clouds of gas and dust too cold to radiate visible light – and which therefore cannot be seen with traditional telescopes. The same problem plagues observations of the chilled-out photons of the cosmic microwave background left over from the big bang. Closer to home, cool, dark objects litter our immediate cosmic neighbourhood.

To obtain a complete picture of our surroundings, astronomers must resort to the equivalent of night-vision goggles or a thermal-imaging camera. These are specialised space telescopes that scan the sky at infrared and microwave wavelengths much longer than those of visible light, allowing them to spy out the faint traces of heat that dark bodies imprint on the sky.

On 29 April [Note: this date has been postponed to mid May since the time of writing], the European Space Agency (ESA) will launch two such instruments from its base on the coast of French Guiana. Piggy-backing in the nose of a single Ariane V rocket will be the Planck microwave telescope and an infrared telescope, the Herschel Space Observatory. Once in space, the two will go their separate ways: Planck to study in detail the cosmic microwave background, and Herschel to spy on the cool gas and dust clouds that are the nurseries of stars and galaxies.

This second satellite will incorporate the largest space telescope ever launched, named …