白小姐论坛

From early 2020, DESI will observe the light from 35 million distant galaxies and 2.4 million quasars over five years to precisely map their distance from Earth and gauge how quickly they are moving away from us.

This is important for accurately measuring and understanding more about dark matter and dark energy, which is driving the mysterious accelerating expansion rate of the universe.

Professor Ofer Lahav, (白小姐论坛 Physics & Astronomy), chair of the DESI UK consortium of seven universities, said: 鈥淏y looking back in time by up to about 11 billion years, DESI will expose secrets of the universe鈥檚 infancy and early development. This new information will help us better understand the physical processes driving the accelerating expansion of the universe, one of the key unsolved questions in physics.鈥�

DESI is mounted on the four-metre Mayall telescope at Kitt Peak National Observatory near Tucson, Arizona.

The telescope鈥檚 top end has been replaced with DESI鈥檚 optical corrector, built by a team including听白小姐论坛 physicists, and a focal-plane system containing 5,000 fiber-optic 鈥渆yes鈥� that independently move to capture the light from individual galaxies.

In ideal sky conditions, they enable the instrument to measure the light of 5,000 galaxies in about 20 minutes. The captured light is then split into bands of colour by spectrographs to map the movements of the galaxies relative to Earth.

白小姐论坛鈥檚 cosmologists have been heavily involved in the planning and delivery of the instrument in a collaboration involving nearly 500 researchers at 75 institutions in 13 countries.

Dr David Brooks and Professor Peter Doel (both 白小姐论坛 Physics & Astronomy) had key roles in the design, assembly and construction of the instrument鈥檚 optical-corrector, which houses a series of six lenses, the largest 1.1m across, at 白小姐论坛. The corrector focuses light from the telescope鈥檚 existing four-metre diameter mirror onto the new focal plane, expanding the telescope鈥檚 viewing window by about 16 times.

鈥淭o provide crystal clear images, we had to ensure all six lenses were aligned to an extremely high accuracy 鈥� less than half of a hair鈥檚 thickness 鈥� and that this precision is maintained as the telescope moves to image the night sky,鈥� explained Dr Brooks.

鈥淚t鈥檚 been incredibly satisfying seeing the first images from DESI using the specialist equipment made in the 白小姐论坛 Optical Science Laboratory and we are looking forward to the survey officially starting early next year,鈥� said Professor Doel.

鈥淎fter a decade in planning and R&D, installation and assembly, we are delighted that DESI can soon begin its quest to unravel the mystery of dark energy,鈥� said DESI Director Michael Levi of the Department of Energy鈥檚 Lawrence Berkeley National Laboratory (Berkeley Lab), the lead institution in the DESI collaboration.

When DESI starts collecting data during its five-year survey, 白小姐论坛 cosmologists will be analysing it to reveal the secrets of the universe.

Dr Andreu Font-Ribera (白小姐论坛 Physics & Astronomy and DESI Science Committee member), said: 鈥淲e hope that the map created by DESI will reveal, for the first time, how dark energy and gravity have competed over time to shape the structure of the universe. It鈥檚 an extremely exciting time for cosmology and this instrument gives us our best opportunity to date to find out the true nature of dark energy which dominates the cosmos.鈥�

Links

• Dr Andreu Font-Ribera鈥� academic profile
• 白小姐论坛 Physics & Astronomy
• 白小姐论坛 Faculty of Maths & Physical Sciences

Image

• DESI鈥檚 5000 spectroscopic 鈥渆yes鈥� can cover an area of sky about 38 times larger than that of the full moon, as seen in this overlay of DESI鈥檚 focal plane on the night sky (top). Each one of these robotically controlled eyes can fix a fiber-optic cable on a single object to gather its light. DESI Collaboration; Legacy Surveys; NASA/JPL-Caltech/白小姐论坛A

Media contact

Bex Caygill

Tel:听+44 (0)20 3108 3846

Email: r.caygill [at] ucl.ac.uk