A new space telescope called Euclid, an ESA (European Space Agency) mission with NASA, is scheduled to launch in July to investigate why the expansion of the universe is accelerating. Scientists call the unknown cause of this cosmic acceleration “dark energy”. In May 2027, NASA’s Nancy Grace Rome Space Telescope will join Euclid to explore this mystery like never before.

“Twenty-five years after its discovery, the accelerating expansion of the universe remains one of the most pressing mysteries in astrophysics,” said Jason Rhodes, senior scientist at NASA’s Jet Propulsion Laboratory in Southern California. Rhodes is assistant scientist of the Rome project and scientific director of the Euclidean project. “With these future telescopes, we will usher in a new era of research into this mystery by measuring dark energy in many different ways and with greater precision than ever before.”

Scientists aren’t sure whether the accelerating expansion of the universe is due to an extra energy component or whether it indicates that our understanding of gravity needs to change somehow. Astronomers will use Roman and Euclid to test both theories simultaneously, and scientists expect both missions to reveal important information about the fundamental workings of the universe.

Euclid and Roman were designed to study cosmic acceleration, but they use different and complementary strategies. Both missions will create 3-D maps of the universe to answer fundamental questions about the history and structure of the universe. Together, they will be much stronger than each of them.

Euclid will observe a much larger area of ​​the sky — about 15,000 square degrees, or about a third of the sky — in both the infrared and optical bands, but with less detail than Roman. It will look back 10 billion years when the universe was about 3 billion years old.

The largest probe in the Roman core will be able to explore the universe with much greater depth and precision, but in a much smaller space – about 2,000 square degrees, or one-twentieth of the sky. Its infrared vision would have opened up the cosmos when it was 2 billion years old, revealing even more faint galaxies. While Euclid focuses solely on cosmology, Roman will also explore nearby galaxies, find and explore planets in our galaxy, study objects on the outskirts of our solar system, and much more.

Hunting for dark energy

A fact discovered by Belgian astronomer Georges Lemaître in 1927 and by Edwin Hubble in 1929 is that the universe has been expanding since its birth. But scientists hoped that the gravity of the universe’s matter would gradually slow this expansion. In the 1990s, scientists looking at a particular type of supernova discovered that dark energy began to increase its impact on the universe about 6 billion years ago, and no one knows how or why. Accelerating means something fundamental is missing from our picture of the cosmos.

Romanus and Euclid would separately provide compelling new data streams to fill gaps in our understanding. They will try to identify the cause of the cosmic acceleration in several different ways.

First, both Roman and Euclid will study the deposition of matter using a technique called weak gravitational lensing. This phenomenon of light bending occurs because anything with mass deforms the fabric of space-time; the greater the mass, the greater the distortion. Images of a distant source produced by light passing through these deformations also appear distorted. When the closest “lensing” objects are large galaxies or galaxy clusters, background sources can appear blurry or create multiple images.

Less concentrated mass, such as dark matter clumps, can produce more subtle effects. Roman and Euclid will study these smaller perturbations to create a three-dimensional dark matter map. This will provide clues about cosmic acceleration as the gravitational force of dark matter, which acts as the cosmic glue holding galaxies and galaxy clusters together, counteracts the expansion of the universe. Counting the universe’s dark matter against cosmic time will help scientists better understand how push and pull feeds cosmic acceleration.

The two missions will also examine how galaxies came together in different cosmic eras. Using measurements of the nearby universe, scientists have discovered a pattern for how galaxies merge. For any given galaxy today, we are about twice as likely to find another galaxy a little closer or further away, about 500 million light-years away.

This distance has increased over time due to the expansion of space. Looking deeper into the universe, into early space ages, astronomers can study the preferred distance between galaxies in different ages. You will see the history of the expansion of the universe by looking at how it has changed. Observing how clusters of galaxies change over time will also provide a definitive test of gravity. This will help astronomers distinguish between the unknown energy component and various modified theories of gravity as explanations for cosmic acceleration.

Roman will do additional research to find many Type Ia supernovae, a special type of exploding star. These bursts peak at similar intrinsic brightnesses. This allows astronomers to determine how far away supernovae are simply by measuring how bright they are.

Astronomers will use Roman to study the light from these supernovae to see how fast they are moving away from us. Scientists will track cosmic expansion over time by comparing how quickly they recede at different distances. This will help us better understand whether and how dark energy has changed throughout the history of the universe.

a strong couple

The investigations of the two missions will overlap, and Euclid will likely observe the entire area Roman will scan. This means that scientists can use Roman’s more sensitive and accurate data to apply corrections to Euclid’s data and spread the corrections over a much larger area of ​​Euclid.

“Euclid’s first glimpse into the vast sky area he will explore will provide a scientific approach to analysis and research for Roman’s deeper dive,” said NASA Project Scientist Mike Seifert for NASA’s Jet Propulsion Laboratory Euclidean Contributions.

“Together, Euclid and Roman will be much more than the sum of their parts,” said Yun Wang, a senior scientist at Caltech/IPAC in Pasadena, California, who leads the galaxy clustering science teams for Euclid and Roman. “Combining their observations will give astronomers a better idea of ​​what’s really going on in the universe.”

The Euclidean mission includes three NASA-backed science teams. JPL spearheaded the purchase and delivery of NISP detectors, as well as designing and manufacturing electronics for the Near Infrared Spectrometer and Euclidean Photometer (NISP) sensor chip. These detectors were tested at NASA’s Goddard Space Flight Center. The Euclidean Science Center (ENSCI) at IPAC at NASA’s California Institute of Technology will support research in the US using Euclidean data. Source