A space telescope is scanning the entire universe to understand dark matter and dark energy

This weekend saw the launch of the European Space Agency’s (ESA) Euclid mission: a space telescope aimed at revealing the mysteries of dark matter and dark energy. The 2.2-ton spacecraft with its 1.2-meter telescope was lifted into space by a SpaceX Falcon 9 rocket and is now on its way to orbit around the sun.

The mission was originally to be launched using a Russian Soyuz rocket from the European Spaceport in French Guiana, but after the Russian invasion of Ukraine, cooperation between ESA and Russia ceased. So instead, the telescope launched from Space Force Station Cape Canaveral in Florida, and blasted off at 12:11 a.m. ET on Saturday, July 1.

The telescope is heading to an orbit called L2, the second Lagrangian point, the same orbit used by the James Webb Space Telescope and other space telescopes. This orbit provides a high stability which is especially important for a mission like Euclid that aims to collect very detailed observations of the universe.

Euclid must reach the second level in four weeks, then make preparations for two months before starting scientific observations around the beginning of October.

Euclid will conduct wide and deep surveys of the universe, piecing together images to create a map of the universe to help identify two mysterious concepts: dark matter, which makes up about 27 percent of everything in existence, and dark energy, which accounts for about 68 percent of the universe. Every atom, molecule, and piece of matter that we can observe makes up the tiny remaining 5 percent known as ordinary or baryonic matter.

We know that dark matter and dark energy must exist because of the motions of galaxies and the way the universe is expanding. However, it is very difficult to study because dark matter does not interact with light and dark energy is an unknown form of energy. So to find evidence of it, we need to look very broadly.

“If you want to do cosmology and observe the universe as a whole, you need to do a big survey,” Giuseppe Racca, ESA’s Euclid Project Manager, explained in a press briefing. “And Euclid specially designed a wide-angle telescope to cover most of the observable universe in a very short time.”

The Euclid telescope will survey 36 percent of the sky during its six-year mission, and to spot a large area the telescope has a very wide field of view. This refers to the amount of sky observable through a telescope, and in Euclid’s case the field of view is 2.5 times the size of the Moon.

Compare that with, say, the Hubble Space Telescope, which has a field of view no more than 1/12 the size of the Moon. The Hubble telescope can image things like galaxies or nebulae in great detail, but it would take about 1,000 years to scan a comparable area of ​​the sky for Euclid.

And if you’re wondering why Euclid surveyed just over a third of the sky, it’s because it’s impossible to see distant galaxies in other regions of the sky, because these distant objects are obscured by the closer stars and dust inside our own. galaxy.

Euclid will have two instruments: the Visible instrument, or VIS, which operates in the visible light wavelength, and the Near Infrared Spectrometer and Photometer, or NISP, which operates in the near infrared. Covering these two wavelengths allows the researchers to see galaxies that are redshifted, which means that as they move away from us, the light from them is toward the red end of the spectrum.

By combining observations from both devices, Euclid’s observations can be used to create a 3D map showing the distribution of visible matter in the universe.

But dark matter is invisible – which is why it’s so hard to study. They cannot be observed directly, but their existence can be inferred by looking at the distribution of matter that we can see.

“Dark energy and dark matter reveal themselves through the very subtle changes they make in the appearance of things in the observable universe,” explained René Lorig, Euclid Project Scientist.

The two main methods for studying dark energy and dark matter that Euclid uses are weak lensing and galaxy clustering. Using two methods to examine the same thing allows the researchers to check their results against each other and, hopefully, yield more accurate results.

Gravitational lensing is an effect in which the gravity of very large objects such as galaxies or galaxy clusters warps space-time, acting like a magnifying glass and altering the light coming from distant objects behind the foreground object.

By seeing how strong this lensing effect is, scientists can calculate the mass of the foreground object — and they can compare this calculated mass with the mass of visible matter in the foreground galaxy. If there is a significant difference between the calculated masses and the observed masses, this indicates the presence of large amounts of dark matter in the foreground.

Another effect, galaxy clustering, refers to how galaxies are distributed in three dimensions across the universe. As the universe expands, galaxies are moving away from us, causing a redshift. Scientists can compare the actual distance to a galaxy with its redshift using a phenomenon called acoustic baryon oscillations, and this can show how fast the universe is expanding — which is directly related to dark energy.

Combined, these methods should help cosmologists learn more about dark matter and dark energy than ever before. To collect the data, Euclid will take about a million images from 12 billion objects during its mission. That should get us one step closer to being able to detect and study these elusive phenomena, and to understanding the make-up of the universe around us.

“It’s more than just a space telescope,” Lorigis said, “it’s really a dark energy detector.”