Euclid Telescope Maps More Than 900m Galaxies and 15,000 Cosmic Lenses

The European Space Agency's Euclid mission has published its first major batch of data, and it contains more than 900m galaxies, The Guardian reported. The release also includes about 15,000 potential cases of strong gravitational lensing, a phenomenon researchers hope will help them understand the "dark universe."

Euclid was launched in July 2023 to build the largest cosmic map ever made, covering a third of the sky and more than 10bn years of cosmic history.

What is Euclid trying to do?

The mission aims to shed light on dark energy and dark matter, two of the biggest mysteries in science. They are thought to make up about 70% and 25% of the universe respectively, according to The Guardian.

Prof. Andy Taylor of the University of Edinburgh, who leads the UK science ground segment for the mission, said other surveys of the sky are bigger, but none matches Euclid's detail and information content.

What is in the new data release?

The release covers about 14% of the total sky area Euclid will eventually map. Within it are more than 900m galaxies and more than 60m potential quasars, which are bright objects at the centers of distant galaxies powered by supermassive black holes.

Taylor described it as the biggest high-resolution image of the universe ever produced. He contrasted it with the Hubble telescope, which delivers images of remarkable resolution but covers a much smaller area of sky. Euclid, he said, keeps that sharpness while mapping huge volumes of the universe.

What is strong gravitational lensing?

It happens when one galaxy, often inside a galaxy cluster, sits in front of a more distant one. As Einstein predicted, the foreground galaxy's gravity distorts space-time and bends the light of the background galaxy, producing bright arcs or rings.

Dark matter strongly boosts the effect because it adds to a galaxy's mass and therefore its gravitational pull.

Why does it matter?

Lensing offers a way to test ideas about what dark matter is. Taylor said that because the effect depends on how dark matter is spread through a galaxy, which in turn depends on its properties, studying lenses may allow scientists to rule out some theories.

Stephen Serjeant, a professor of astronomy at the Open University, agreed. He said lensing reveals how dark matter clumps, which is a strong clue to its type, because different kinds of matter clump differently. He said there is a good chance, though not a certainty, that the next breakthrough on dark matter will come from strong lensing.

The scale is a leap from earlier work. Researchers previously knew of about 1,000 cases of strong lensing, while the Euclid release holds about 15,000 probable ones. Taylor said an estimated 170,000 are expected to be found by the end of the mission. These are candidates, not confirmed cases.

What comes next?

Taylor said another data release is expected next summer. It is due to include results on how galaxies are distributed and on weak gravitational lensing, the subtle distortion of distant objects by dark matter in the foreground.

Scientists can use that pattern of distortion to map where dark matter lies across the universe, Taylor said, then work out its statistical properties and compare them with different theories. Different types of dark matter and dark energy should leave slightly different patterns on the sky.

The sheer volume of data is also a challenge. Taylor said the dataset has grown too large for any person to inspect it all, which means many objects and phenomena remain to be discovered.

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Around Prague, based on reporting by The Guardian