Euclid releases data on 900 million galaxies for a 3D cosmos map

Takeaway: The spectra provide the coordinates and properties needed to assemble the cosmic map over time.

Why do the lens candidates matter?

A massive foreground object, such as a large galaxy, can bend the fabric of space-time. That curvature magnifies, distorts and sometimes duplicates light from objects behind it. These arrangements, called Einstein rings after the physicist who predicted them, act like natural magnifying glasses.

Euclid's first release identifies more than 15,000 strong gravitational lensing candidates. Such lenses can give astronomers clearer views into the deep universe than a telescope could provide on its own.

The candidate label matters. This is not yet a final tally of confirmed lenses, and each candidate still requires further study before its properties can be established.

Natalie Lines, a Euclid Consortium member working at the University of Portsmouth in the United Kingdom, said: “Over 10 years ago, we forecast that Euclid would revolutionise the field of strong lens discovery. That day is finally here.”

Takeaway: Euclid has identified a promising population of cosmic magnifying glasses for follow-up work.

What do the first images show?

Messier 81, or M81, is one of the brightest galaxies in the sky. Its fully developed spiral arms extend toward a bright core, earning it the description “grand design spiral.” M81 is close enough to Earth to be seen with a good pair of binoculars.

Euclid's wider view places M81 on the right, the elliptical galaxy NGC 3077 at the lower left and crisp clouds of interstellar dust around them. The image shows how the telescope captures structures at different scales within the same field.

Among the nearly 1 billion galaxies in the release is NGC 1291, also known as the Golden Eye galaxy. It lies 33 million light-years from Earth, the distance light travels in 33 million years. Euclid has captured it at the telescope's highest resolution so far.

Ring galaxies like NGC 1291 have a central bulge separated from a surrounding ring of stars. Astronomers think they form when a smaller galaxy passes through the middle of a larger one.

Takeaway: The images show both nearby structures and distant galaxies that future maps will place within a larger three-dimensional context.

How much of the survey remains?

A survey image in the release shows the entire sector of the Euclid Wide Survey, which maps broad areas of the northern sky. Its companion, the Euclid Deep Survey, will spend about 10% of the telescope's observing time taking repeated observations of three relatively small sky fields.

The two-part design combines breadth with depth: the Wide Survey covers enormous areas, while the Deep Survey revisits smaller regions in greater detail. Euclid remains on track to assemble one of the most comprehensive cosmic datasets ever produced.

The scientific payoff now depends on researchers analyzing these observations, testing the lens candidates and building the 3D map. Much of that work lies ahead.

Takeaway: Most of Euclid's observing time and six-year mission remain, leaving substantial room for new discoveries.