Cosmologist to help solve one of the Universe’s biggest puzzles

New research led by the University of Portsmouth could solve one of the biggest outstanding puzzles about the universe and also radically rewrite our understanding of our place within it.

Professor Kazuya Koyama from the University’s Institute of Cosmology and Gravitation is leading a project called CosTesGrav, which is using observations of distant galaxies to help develop new theories that modify Albert Einstein’s general theory of relativity so it works on large scales.

A Hubble Space Telescope image of the barred spiral galaxy NGC 1300, located 61 million light years away. Credit: HST / NASA / ESA

The research could solve one of the biggest outstanding puzzles about the Universe.

“General relativity is a very good theory to describe gravity,” said Professor Koyama. “But when we apply it on a large, cosmological scale, we see some very strange things that we need dark energy to explain. The problem is that we have no idea what dark energy is.”

They will use data from a new space telescope called Euclid, which is due to be launched by the European Space Agency in 2021, to capture images of billions of distant galaxies to provide new insights into how gravity works in the depths of space.

The CosTesGrav researchers are using observations of galaxies that are up to 3.3 billion light years (20 sextillion miles) away to look for tiny distortions in their shape caused by gravity.

The general theory of relativity states that light is bent by gravity, meaning that it can leave a distinctive signature in the light emitted by distant astronomical objects like galaxies.

The CosTesGrav team have already used images from the Hubble Space Telescope to look for some of these distortions and found that the signature left by gravity is consistent with general relativity.

But Professor Koyama believes that larger-scale surveys like those conducted by Euclid could allow them to detect distortions that indicate there may be something else at work.

“We need to explain the success of general relativity on small scales but at the same time modify it over very large scales,” he said. “It is a challenge. We have two approaches – one is to come up with theoretical models and use state-of-the art simulations to test them.

“The other is to use the observations and look for the signatures of a deviation from general relativity.”

He says that combining these approaches will enable the researchers to capitalise on Euclid’s highly accurate maps of the distribution of galaxies and test general relativity on a cosmological scale.

Read more about Professor Koyama’s work in the latest issue of Horizon, the EU research and innovation magazine –

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