Durham scientists go dark with DESI


A team of researchers from Durham have contributed to the construction of a cutting-edge telescope to be used for the creation of the most detailed 3D map of the universe to date. Featuring 5,000 fibre-optic ‘eyes’, the “Dark Energy Spectroscopic Instrument” (DESI) will be able to measure the expansion rate of the universe to an as-yet unreached level of precision. 

The nature of our expanding universe is a relatively recent discovery, with a fascinating story behind it. Celestial objects (such as galaxies) approaching the Milky Way are ‘blue-shifted’ due to the higher frequency of light, whereas objects moving away are ‘red-shifted’, with lower light frequencies. In the early 1900s, when astronomers such as Edwin Hubble were able to use sufficiently advanced telescopes to observe the heavens in detail, it was expected that celestial objects such as galaxies would be moving towards or away from us at random depending on their trajectories. 

However, when Hubble took a look at the sky, he was shocked – everything was red-shifted, indicating the rest of the universe was moving away from us at a rapid pace. Not only that, but galaxies further away were more red-shifted than those closer, suggesting the further away from Earth an object is, the faster it is moving away from us!

DESI is able to cycle through 5,000 galaxies in 20 minutes

This finding indicated that the universe is expanding, with the space between galaxies simply getting larger over time, causing the rapid movement of these objects away from one-another, very similar to any sane person on Jimmy’s dancefloor when a fresher starts chunning. The expanding universe discovery laid the groundwork for the big bang theory, a logical deduction that an expanding space must have originated from a much smaller, single point in its distant past.

The expansion of the universe was a larger surprise than it seems, as the very nature of gravity suggests that objects will be pulled together, rather than pushed apart. What hidden force was powering this rapid expansion? Modern theories suggest that dark energy is the major agent behind this conundrum, with recent demonstrations even showing the universe’s expansion is speeding up (scientists are still stumped as to why!).

DESI seeks to measure the effects of dark energy, hopefully facilitating greater understanding of the universe as a whole.

Installed on the four-metre Mayall Telescope in Arizona, DESI will be able to photograph galaxies up to 11 billion light years away, taking a peek back in time at the early universe.

The researchers were part of a collaboration of scientists from 75 institutions in 13 countries. The Durham team, led by Dr Luke Tyas, focused on the fibre-optic system, critical to splitting observed light into narrow bands, allowing measurements of the distance from Earth of any observed objects.

By looking at how fast and how far galaxies are moving away from Earth, researchers can begin to make precise measurements of how fast the universe is expanding. DESI is able to cycle through 5,000 galaxies every 20 minutes, hopefully collecting ten times more data on galaxies than humans have collected to date.

Researchers can now make precise measurements of how fast the universe is expanding

Professor Carlos Frenk, part of the Durham DESI team, said: “The DESI project epitomizes the best of modern science. It is designed to answer a fascinating question about the fundamental fabric of our universe: what is causing the cosmic expansion to speed up?…Bringing together scientists from 13 countries, DESI shows how people from across the globe can come together to tackle key scientific questions.”

Final testing of DESI has recently begun, with formal observations set to occur in 2020. What will we find by looking so far back into the past of our universe, and what will it mean for the future of dark energy and astronomy as a whole? 

Image by Fan D via Flickr

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