Illustration: ESA - C. Carreau

Scientists from The Open University form part of The European Space Agency (ESA) collaboration to build Euclid, a satellite which will help answer the important question on why the Universe is expanding at an accelerating rate, rather than slowing down due to the gravitational attraction of all the matter in it.

Andrew Holland, Professor of Electro-Optics at The Open University’s Centre for Electronic Imaging, said: “Cosmic acceleration was discovered in 1999, but we still don’t know what causes it. The term ‘dark energy’ often describes this force, and the Euclid collaboration between academia and industry will study the ‘dark Universe’, looking at the evolution and distribution of dark matter and dark energy.

“Scientists have recently come to the startling conclusion that ordinary matter - that is protons, neutrons, electrons and atoms that we understand well - account for only 4% of the known Universe; the remaining 96% is thought to be made up of the mysterious dark energy and dark matter.”

The Euclid spacecraft, a European venture led by ESA, will survey the sky, and a visible imaging instrument known as VIS will measure the shapes of distant galaxies using a digital camera with a large array of detectors called CCDs. The detectors, manufactured by Chelmsford-based e2v technologies PLC, will measure the precise shape of those galaxies. Foreground galaxies warp the space and time around them, according to Einstein's theory of gravity, and the shapes of background galaxies appear subtly distorted by these foreground warps. By measuring these subtle warps, Euclid will enable direct measurements of the amount and nature of dark energy in the Universe.

The harsh radiation environment around the spacecraft arising from the sun, often referred to as ‘space weather’, can adversely affect the CCD detectors, and with funding from the UK Space Agency, The Open University research team will start a five year programme to make detailed measurements of the radiation effects. Working in collaboration with e2v for detector manufacture, the research group will help UK industry achieve the best performance from their detectors. This will enable calibration and correction of the resulting images, so that any elongation measured by Euclid accurately predicts the presence of dark matter.

Euclid has now been adopted as an official ESA mission and solidifies the Euclid Consortium at the forefront of worldwide research into the ‘Dark Universe’. The satellite is due to launch in 2019.

Supplementary Information:

Euclid Mission
Euclid is an M-class mission and is part of the ESA Cosmic Vision programme 2015-2025. Euclid is a 1.2m space telescope, located at 2nd large Sun-Earth Lagrange point, and will perform two major surveys of the sky over at least 5 years. The wide survey will cover 40% of the whole sky and is focused on mapping the locations and shapes of billions of galaxies. The Euclid deep field will cover a patch of the sky approximately 100 times the size of the full Moon (or 15,000 times larger than the Hubble Ultra Deep Field), to unprecedented depths. The combination of depth and sky coverage will enable Euclid to detect very rare sources like extremely high redshift quasars, and maybe the first galaxies that ever formed.

Dark Universe
For nearly 80 years now, astronomers have known about “dark matter”; matter than does not shine or reflect light and can only be detected through its gravitational influence. Scientists still do not know the true physical nature of dark matter, but its existence has been confirmed numerous times over the last few decades. In 1999, astronomers found evidence for an even stranger component to the dark universe, namely “dark energy” that appears to driving the expansion of the Universe faster and faster. This “dark energy” makes up three quarters of the energy budget of the Universe; three times the energy associated with dark matter and over 20 times the energy in normal matter like atoms. There are many ideas of what it could be, but so far there is no compelling explanation for the nature of this mysterious substance in the Universe. Astrophysicists believe that the discovery of its very nature will revolutionize fundamental physics and our knowledge of the physical laws of nature.