Frequently asked questions about Euclid
Why are we interested in dark matter and dark energy?
Scientists discovered that the distribution and movement of objects in the Universe, like stars and galaxies, are affected by the presence of two invisible entities that they named dark matter and dark energy. These names indicate that the scientists do not know what these forms of matter and energy are. If we want to understand the Universe we live in, we need to learn more about the details of these ‘dark’ entities and uncover their nature.
What can Euclid do that the James Webb Space Telescope cannot?
Where Webb can observe extremely far back in time and zoom into the details, Euclid can go fast and wide. In a single observation Euclid can record the data from an area of the sky more than one hundred times bigger than that imaged by Webb’s camera, NIRCam. This means that Euclid can map a third of the sky to the required sensitivity in six years in space – a feat that would be impossible with Webb.
What will Euclid’s image quality be?
Euclid’s images will be at least four times sharper than those achieved by ground-based sky surveys. In the absence of Earth’s atmosphere, and with optics of the highest quality, the angular resolution of a telescope is determined by the size of its primary mirror. Since Euclid has a smaller primary mirror than the Hubble Space Telescope, it will resolve fewer fine details, but the image quality will be outstanding and the lower resolution will be adequate to achieve its scientific goals. The telescope and its optics are designed to deliver a large field of view and a stable image quality throughout the survey.
Why must Euclid observe so many (billions of) galaxies?
This is necessary to build a detailed map of the distribution of matter in the Universe. It is also needed to record how fast all these cosmic objects are receding from each other, over a large area of the sky and across distances of 10 billion light years. Only with such an extensive map of the large-scale structure of the cosmos can we pin down the characteristics of dark energy and dark matter, and possibly spot deviations from the laws of gravity as we currently know them (described by the theory of General Relativity).
Will Euclid build on the results of ESA’s Planck mission?
Planck’s results are a fundamental starting point for the investigations enabled by Euclid. Using the observations made by the Planck mission of the temperature fluctuations of the Cosmic Microwave Background and of its polarisation properties, scientists were able to fundamentally improve our understanding of the initial phase of the Universe and gain further evidence of the presence of dark energy and dark matter. But the question of what these entities are, remains. Euclid is about to pick up the baton from Planck and help us further our understanding of the Universe we live in.
Will Euclid study black holes?
Euclid will be able to study giant black holes at the centre of galaxies by observing the magnified and distorted shapes of background galaxies whose light passes in the vicinity of the black hole and is affected by strong gravitational lensing. Additionally, thanks to its observations of the effects of weak lensing and galaxy clustering, Euclid will be able to test theories that predict the existence of primordial black holes. These are hypothetical smaller black holes that could have formed soon after the Big Bang and could be (partially) the origin of dark matter.
What is the relation between the Euclid mission and ground-based surveys with similar scientific goals?
Thanks to its vantage point outside Earth’s atmosphere, Euclid will be able to perform the most comprehensive study of dark energy and dark matter. There are, however, mutual benefits between the Euclid mission and ground-based surveys, and scientists in the Euclid collaboration will also make use of observations from partners ground-based surveys for the study of the Universe. In particular, the area of the Euclid survey has been defined to achieve great overlap with the 10-year Legacy Survey of Space and Time that will be conducted by the Vera C. Rubin Observatory in Chile.
Why is the nominal mission duration six years?
To accomplish its scientific goals and build a detailed map of the large-scale structure of the Universe, Euclid needs to examine billions of galaxies. This can only be achieved by observing a very large area of the sky (approximately a third of the sky). Euclid needs six years to observe the designated area of sky with the required sensitivity.
Can Euclid serve other scientific investigations besides cosmology?
Definitely! Euclid will provide a gigantic catalogue of billions of galaxies by imaging these at different wavelengths of visible and near-infrared light, and of foreground stars in our galaxy. This treasure trove of data can be used to improve our understanding of many aspects of astronomy. Some examples include the detection of cool stars in our galaxy such as brown dwarfs, the study of the merging history and evolution of galaxies, the investigation of stellar populations, the study of supernovae and variable sources, and even the detection of exoplanets or meteoroids (as illustrated on the website of the Euclid Consortium).
How far can we see with Euclid?
In the main (wide) survey Euclid will detect objects as far as 10 billion light years from us (corresponding to a redshift of 2 to 2.5). In the deep survey it will be able to detect objects as far as 13 billion light years (redshift 6 to 8) away. In this infographic, you can see the areas of the sky that Euclid will observe for the wide and deep surveys.
Do dark matter and dark energy affect my everyday life?
No. If dark matter is indeed made of particles, it interacts so rarely with normal matter (that we, animals, plants and the entire planet are made of) that it can be completely and safely ignored. The effects of dark energy can only be perceived by astronomical sources over distances of 100 million light years, so again it can be safely ignored at the human scale (but also at the scale of our Solar System). However, it is because of dark matter and dark energy that the Universe has evolved the way it has, so if we want to understand the Universe we live in, we need to uncover their nature.
What does ‘Euclid is an ESA mission’ mean?
Euclid is a mission developed and operated by ESA, with Thales Alenia Space as prime contractor for the construction of the satellite and its service module. Airbus Defence and Space developed the payload module, including the telescope.
The Euclid Consortium provided the two onboard scientific instruments VIS and NISP and will lead the scientific data analysis. NASA provided the near-infrared detectors of the NISP instrument.
More than 2000 scientists from 100 institutes are part of the Euclid Consortium and will participate in the scientific harvest of the mission. The Consortium comprises scientists from many European countries: Austria, Belgium, Denmark, France, Finland, Germany, Italy, the Netherlands, Norway, Spain, Switzerland, Portugal, Romania and the UK. The Consortium also includes teams of scientists from the US, Canada and Japan.