Spiral galaxy IC 342: Over its lifetime, our dark Universe detective will image billions of galaxies, revealing the unseen influence that dark matter and dark energy have on them. That’s why it’s fitting that one of the first galaxies that Euclid observed is nicknamed the ‘Hidden Galaxy’, also known as IC 342 or Caldwell 5. Thanks to its infrared view, Euclid has already uncovered crucial information about the stars in this galaxy, which is a look-alike of our Milky Way.
While the James Webb Space Telescope has been delivering incredible new images of the sky, it’s not the only new space telescope on the block.
Launched in 2023, the European Space Agency’s Euclid telescope released its first batch of images in late May which has already resulted in some groundbreaking scientific results.
Its large field of view enables it to cover a wide range of interstellar objects.
Each image covers over 100 times the size of a James Webb image, allowing us to investigate a large part of the sky in a fraction of the time it takes with a ground-based telescope.
Euclid has a 1.2-metre mirror, smaller than the NASA flagships, Hubble, and James Webb space telescopes.
Putting telescopes into space delivers many advantages over ground-based telescopes, where the Earth’s atmosphere blurs and absorbs light.
Still, up in space, that mirror can take images four times sharper than the best ground-based telescopes, where atmospheric distortions limit images to a resolution of 0.3 arcseconds.
The telescope’s principal mission is to measure the ‘dark’ universe by taking images of billions of galaxies over one-third of the entire sky.
The high resolution allows small, faint galaxies to be distinguished from each other more easily and provides more details about closer galaxies than can be seen from the ground.
Euclid will also take spectra of many of these objects, giving details about how fast they move and what elements they are made up of.
Euclid’s eventual sample of a billion galaxies helps investigate dark matter and energy. The visible Universe, consisting of the stars, gas, and dust that we see, is only 5% of the total stuff in the Universe.
By looking at how closely galaxies are clustered together, we can investigate the effect of dark matter on how galaxies evolve over billions of years.
By separating the sample into galaxies at different distances from the Earth, we can investigate this growth directly by looking at how the concentration of different elements changes over time as stars burn and die.
The speed at which galaxies are moving away from us helps to measure how the expansion of the Universe has changed over time. This gives a better understanding of the nature of dark energy, which causes the acceleration of its expansion rate over time.
While we wait for this huge sample of galaxies to build, Euclid produces results in diverse areas, such as galaxy clusters, nebulae, and even rogue planets.
Its wide field of view and deep imaging lets us observe galaxy clusters such as Abell 2390 more ‘zoomed-out’ than Hubble’s view, allowing us to determine how big the clusters are.
Abell 2390 is a galaxy cluster, a giant conglomeration of many galaxies like the Milky Way. More than 50,000 galaxies are seen here, the distances to which can be measured thanks to these new observations. Each image can contain 50,000 galaxies, so determining which is part of the cluster is difficult.
Still, by analysing the spectra of the galaxies, we can determine those at the same distance from us.
Due to the large amounts of dark matter they contain, these clusters also warp the light from galaxies behind them like a giant magnifying glass.
Thus, these images let us study dark matter in two different ways at the same time: by looking at the cluster galaxies themselves and what is happening to the light from the distant galaxies.
Euclid’s first Early Release Observations contains some fascinating results, and the mission is expected to last another five years.
Combined with the incredible resolution of James Webb and Hubble, Euclid is likely to unearth many news sources that will lead to follow-up studies, shedding a whole new light on the deepest, darkest parts of our Universe.
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