Durham Physics helps Euclid telescope see the invisible

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On 7th November, the European Space Agency (ESA) released five images from the Euclid telescope. Euclid, launched on a SpaceX Falcon 9 rocket in July 2023, is set to make an extensive 3D map of our universe by imaging over one third of the sky.

Named after Euclid of Alexandria, a Greek mathematician often known as the ‘father of geometry’, the telescope is set to explore the geometry of the universe by mapping the distribution of galaxies. Euclid is made up of a 1.2-metre telescope, and two cameras which are sensitive to different wavelengths to allow scientists to see different structures.

The ‘regular’ matter (ourselves, stars, planets etc.) that we see in day-to-day life makes up only 5% of the content of the Universe. Dark matter outweighs its visible counterpart by nearly six times, taking up 27% of the Universe. Dark energy takes up the highest proportion, 68%, and is responsible for the acceleration of the universe’s expansion. Euclid is studying our dark universe by investigating the spread of galaxies within it, to find the distribution of matter.

Dark matter is an invisible form of matter meaning galaxies do not fall apart as they spin; without an extra contribution from ‘invisible’ matter, galaxies currently spin at a speed that would cause them to fly apart. We cannot directly see dark matter as it does not emit, reflect, or absorb light but we know of its existence due to the gravitational effect it has on things we can see.

Dark matter may exist in different forms akin to the periodic table of elements

A recent paper, published in October, has proposed a theory to suggest that dark matter particles may exist at different masses, speeds and with varying interactions forming a group akin to the periodic table of elements. Though experimental evidence of this is a long way off, it is suggested that different species of dark matter formed in different phases of the early universe.

The Euclid Consortium, made up of 13 European countries as well as the US, Canada, and Japan, alongside ESA will be running the mission over the course of its six- year lifetime. Professor Richard Massey of Durham’s Department of Physics is a founding member of the Euclid Consortium who has been involved in the design and development of the mission for about 20 years.

Durham has aided the mission by using supercomputer simulations to create mock data to train the analysis software which will be compared against the real observations from Euclid. Additionally, Durham has contributed to the radiation monitoring and mitigation strategy of the mission by improving Euclid’s cameras’ tolerance to high radiation environments.

An image of the Perseus cluster of galaxies has been published in unprecedented detail with over 100,000 galaxies in the background, some of which are over 10 billion lightyears away. This cluster would not exist without the existence of dark matter because if dark matter did not exist, galaxies would be evenly distributed throughout the universe. Gravity causes dark matter to form thread-like structures which cross over to make up the cosmic web and causes galaxies to stick together, forming a cluster.

Euclid will unlock a wealth of information by mapping our dark universe, including objects we have never seen before

Over the course of the mission, Euclid will image billions of galaxies. In this image release, the ESA have published new images of spiral galaxy IC 342 (below) and irregular galaxy NGC 6822. By observing many galaxies along the cosmic web, we will be able to map the dark matter distribution within our universe.

Euclid is the only telescope that is currently able to observe a whole globular cluster, a group of stars that is held together by gravity, while maintaining distinguishability between many stars within it. This has been demonstrated by the image of globular cluster NGC 6397. Being able to distinguish the stars within the cluster helps shed light on where dark matter may be located as well as the history of the Milky Way.

Additionally, a new image of the horsehead nebula, a cloud of dust and gas acting as a star nursery, has been released. Not only is this new image captivating, but it also gives scientists hope at finding previously unseen Jupiter-mass planets, brown dwarfs, and young stars. The region containing the nebula is of immense interest to scientists as star formation takes place in unique conditions.

The five images released show a range of cosmological structures showcasing how Euclid is performing its job to a very high level. Over the next six years, or potentially longer, depending on the amount of fuel left, Euclid will unlock a wealth of information by mapping our dark universe, including objects we have never seen before.

Image: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO

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