Euclid is a European space telescope that was launched last summer and will create a three-dimensional map of the universe. Euclid must reveal the true nature of two elusive cosmic mysteries: the true nature of dark matter and dark energy, the ‘something’ that makes up about 95 percent of the universe, but of which no one knows exactly what it is.
Unlike the ‘normal’ matter from which everything we know is made – from people to stars – you cannot see dark matter. Astronomers discovered it indirectly, for example because galaxies such as the Milky Way would spin themselves apart without the ‘extra’ gravity of dark matter. Without that gravity, stars would fly out of the system like water out of a salad spinner.
Dark energy, in turn, serves as a kind of cosmic bicycle pump that inflates the universe at a measurably accelerated rate. But no one knows exactly what the true nature of that bicycle pump is.
Euclid must collect fresh measurement data with which astronomers, at least the hope goes, can unveil the true nature of dark matter and dark energy. To this end, the instrument will photograph and analyze many billions of galaxies and the stars in those galaxies.
That is also one of the main differences with that other space telescope that provides beautiful images of the cosmos: James Webb. Where Webb can zoom in on very distant cosmic details with his instruments, Euclid takes a much broader view. In one observation, the space telescope captures a portion of the sky more than a hundred times larger than Webb.
On Tuesday afternoon, ESA unveiled the first color images of the cosmos taken by Euclid. “Never before has a telescope been able to make such razor-sharp astronomical images of such a large part of the sky and to look so far into the distant universe,” ESA said. The images show five mesmerizing vistas that, above all, illustrate that the instrument is working properly.
1. The Perseus Cluster of galaxies
This composition of spots of light conceals the elusive grandeur of the universe. In the foreground – the brighter dots – are visible about a thousand galaxies that are clustered in the so-called perseus cluster, stuck together by their gravity. Each of these systems is comparable to the Milky Way, in which the sun and roughly a hundred billion other stars live out their lives.
About a hundred thousand other galaxies then appear in the background of this image, many of which had not been seen before until recently. It is these kinds of measurements of staggering numbers of galaxies that Euclid needs to reveal how dark energy continues to pump up the universe.
2. The Hidden Galaxy
The spiral galaxy IC 342 is a galaxy nicknamed ‘the hidden galaxy’ because, as seen from Earth, it is hidden behind the brightest part of our own Milky Way. Euclid nevertheless managed to take a photo that, according to the astronomers involved, already reveals new information about the stars in this system.
Euclid must image billions of these galaxies in total to reveal the influence that dark matter has on the stars at their core.
3. The cosmic horse head
This famous nebula, about 1,375 light-years away from Earth, is the closest region in which young stars are forming on a large scale. Although this area has been imaged many times, this photo already reveals more detail than previous images.
The image also illustrates that Euclid can do more than just research dark matter and energy. Scientists hope to use the instrument to discover newborn stars and Jupiter-like planets in this nebula.
4. The ‘irregular’ galaxy
The deeper you go into the universe, the more often you come across galaxies that do not look like a spiral like the Milky Way. This also applies to this galaxy, the so-called Barnard galaxy, which is irregular in shape and relatively small. Euclid will photograph these types of galaxies up to about 10 billion light-years from Earth. This is, by the way, close by cosmic standards: ‘only’ 1.6 million light years away.
5. The ball of stars
This sphere is much smaller than a galaxy and is part of the Milky Way. Such a so-called globular star cluster contains several hundred thousand stars, held together by their gravity. Astronomers hope that detailed observations of these types of star spheres can disentangle the influence of the invisible ‘extra’ gravity of dark matter.