One of the missions I talk about in New Eyes on the Universe is the Euclid telescope. When I wrote the book, Euclid was still a mere possibility. Today, Euclid took one step closer to becoming a reality.
The Science Programme Committee of ESA today formally adopted the mission – meaning that the money is in place to proceed. (In the current economic climate that is a significant step. To build, launch and operate Euclid is going to cost ESA in the region of half a billion pounds; you can add an extra 150 million on top of that for the cameras and spectrometers that Euclid will use.)
And what will we get for all this money? Hopefully, a much better understanding of what dark energy is. Euclid will have a 1.2m mirror and three scientific instruments for observing in the optical and infrared. Its observations will cover half of the entire sky and it will map structures from ten billion years ago up to the present day. The idea is that it will measure the distances to objects using three different methods: primarily through baryon acoustic oscillations but also through observations of type Ia supernovae and weak gravitational lensing. By combining this distance data with redshift data, cosmologists can determine the ‘size’ of the universe at different times in its history. In other words, they can determine the expansion history of the universe. And it’s the careful study of this expansion history that will enable cosmologists to learn more about the mysterious quantity – dark energy – that’s causing the expansion to accelerate.
Euclid should launch in 2019. So in ten years or so we might be better able to answer one of the most puzzling questions in science: what’s causing the universe to blow itself apart?