Euclid's first data release: A stepping stone to its 3D map of the sky

The ESA's Euclid has already teased us with some early results. In the past, it's given us a small image covering 60 square degrees of the sky, created with a few days of observations. Those images showed individual targets from the Horsehead Nebula to the Perseus cluster of galaxies.

But now we have data from more than one year of the telescope's observations, named DR1-Foundation. DR1-Foundation covers a sky area as large as about 9,500 full moons and captures light from more than 1 billion objects. It took about 13 months to gather all these data.

Understanding dark energy and dark matter means studying as much of the universe as possible. The effects of dark energy and dark matter are felt at large scales, and by constructing an image of galaxy superclusters and the filaments they exist on, as well as the voids between those filaments, Euclid will lead to new insights into both dark energy and dark matter.

There are other efforts to map this structure, some dating back decades. DESI, the Dark Energy Spectroscopic Instrument, has created the largest 3D map so far, but Euclid's will be larger. Euclid's will have more depth and volume, and since it's space-based while DESI is ground-based, it won't have to deal with atmospheric interference and will have a higher resolution.

This data release is from Euclid's Wide and Deep Surveys, two surveys that will form the backbone of its 3D map. Even though the data cover 1,900 square degrees of the sky, they only represent about 14% of the sky the space telescope will cover in its six-year mission.

The Wide Survey is Euclid's primary campaign and will cover almost half of the galactic sky. It's an imaging and spectrographic survey in visible and near-infrared light. It's the telescope's main cosmology survey and will cover a large volume to constrain dark energy and dark matter.

The Deep Survey serves a different purpose. It'll find fainter objects like dwarf galaxies, low-mass galaxies and tidal tails, as well as high-redshift galaxies and quasars. It will serve to calibrate the Wide Survey and will provide its own, separate science based on its higher density of sources.

Basically, the Wide Survey provides the greater volume, and the Deep Survey looks more closely and gives more depth. The two combined are needed for a cosmological survey.

Euclid also delivered an image of NGC 1291, a stunning ring galaxy about 33 million light-years away. It's also called the Golden Eye galaxy, and it has an inner ring and an outer ring, as well as an inner bar. Its inner and outer rings may be the result of a merger with a gas-rich galaxy in the past.

Euclid also captured images of Abell 3128. It's 800 million light-years away and contains hundreds of individual galaxies. Massive clusters like this one are important probes for dark energy and dark matter, but especially for dark matter. They serve as important gravitational lenses and reveal a lot about where dark matter is concentrated. They can help cosmologists test Lambda-cold dark matter, which is the standard big bang theory of the universe. They also help Euclid calibrate itself.

We're only at the appetizer of the visual and scientific feast that Euclid will deliver. By the time it's completed, its 3D map of the sky will be visually entrancing and full of science. It's already discovered a new comet and the most ancient quasar in the universe and produced new images of the Milky Way's overpopulated center.

It's off to a strong start and will only get better.