To find out why the cosmos is expanding so quickly, a brand-new space observatory called Euclid, an ESA (European Space Agency) mission with significant assistance from NASA, is scheduled to launch in July. Scientists call the unknown cause of this cosmic acceleration “dark energy.”
By May 2027, NASA’s Nancy Grace Roman Space Telescope will join Euclid to explore this puzzle in ways that have never been possible before.
“Twenty-five years after its discovery, the universe’s accelerated expansion remains one of the most pressing mysteries in astrophysics,” said Jason Rhodes, a senior research scientist at NASA’s Jet Propulsion Laboratory in Southern California. Rhodes is a deputy project scientist for Roman and the U.S. science lead for Euclid. “With these upcoming telescopes, we will measure dark energy in different ways and with far more precision than previously achievable, opening up a new era of exploration into this mystery.”
Whether the universe is expanding more quickly because of an additional energy source or because our concept of gravity has to be altered in some manner is unknown to scientists. Astronomers to simultaneously test both hypotheses will use Roman and Euclid, and it is anticipated that both missions will provide crucial insights into the fundamental principles governing the nature of the cosmos.
Both Euclid and Roman are intended to examine cosmic acceleration, but they do it using various, complementary methods. In order to respond to fundamental inquiries about the universe’s structure and history, both missions will create 3-D maps of the cosmos. Together, they will be much more powerful than either individually.
In comparison to Roman, Euclid will survey a much greater portion of the sky roughly 15,000 square degrees, or nearly one-third of it in infrared and optical wavelengths. It will peer back 10 billion years to when the universe was about 3 billion years old.
Roman’s greatest core survey will cover a smaller area of around 2,000 square degrees, or one-twentieth of the sky, but it will be able to probe the universe with considerably higher precision and depth. With a greater number of fainter galaxies visible, its infrared vision will portray the universe as it was 2 billion years ago.
Twenty-five years after its discovery, the universe’s accelerated expansion remains one of the most pressing mysteries in astrophysics. With these upcoming telescopes, we will measure dark energy in different ways and with far more precision than previously achievable, opening up a new era of exploration into this mystery.
Jason Rhodes
Roman will examine nearby galaxies, identify and research planets throughout our galaxy, study objects on the boundaries of our solar system, and much more whereas Euclid will just concentrate on cosmology.
The dark energy hunt
The universe has been expanding ever since its birth a fact discovered by Belgian astronomer Georges Lemaître in 1927 and Edwin Hubble in 1929. But scientists expected the gravity of the universe’s matter to gradually slow that expansion.
Scientists found that dark energy started expanding its effect on the universe around 6 billion years ago, but no one understands how or why, by studying a certain type of supernova in the 1990s. The fact that it is speeding up indicates that a crucial component is lacking from our current understanding of the universe.
Roman and Euclid will each offer a distinct stream of fresh, intriguing information to close knowledge gaps. They’ll attempt to pin down cosmic acceleration’s cause in a few different ways.
First, both Roman and Euclid will study the accumulation of matter using a technique called weak gravitational lensing. This light-bending phenomenon occurs because anything with mass warps the fabric of space-time; the bigger the mass, the greater the warp.
Additionally, light passing through these warps produces distorted images of a distant source. Background sources may look smeared or split into numerous images when those closer “lensing” objects are large galaxies or galaxy clusters.
Less concentrated mass, like clumps of dark matter, can create more subtle effects. Roman and Euclid will each produce a 3-D dark matter map by examining these minor aberrations. That will provide hints regarding cosmic acceleration since dark matter’s gravitational pull opposes the universe’s expansion by acting as a cosmic glue to hold galaxies and galaxy clusters together. Understanding the push-and-pull feeding into cosmic acceleration will be made easier for researchers by tallying up the dark matter of the universe across cosmic time.
The two missions will also study the way galaxies clustered together in different cosmic eras. Analyses of the local cosmos have shown a pattern in the distribution of galaxies. We are nearly twice as likely to discover a galaxy 500 million light-years away from any galaxy we know of today than one that is a little closer or farther.
This distance has grown over time due to the expansion of space. Astronomers can examine the ideal separation between galaxies at various stages in the universe’s history by gazing farther into the cosmos, to earlier cosmic times. The history of the universe’s expansion will be revealed through observing how it has altered.
A precise test of gravity will also be possible by observing how galaxy clustering changes over time. This will make it easier for astronomers to distinguish between an unidentified energy component and distinct modified gravity theories as causes of cosmic acceleration.
Roman will conduct an additional survey to discover many distant type Ia supernovae a special type of exploding star. These explosions have a comparable inherent brightness peak. As a result, astronomers can gauge the supernovae’s distance by observing how bright they seem.
Roman will be used by astronomers to analyze the supernovae’s light in order to determine how swiftly they appear to be departing from Earth. Scientists will be able to chart the evolution of cosmic expansion by measuring how quickly objects are expanding at various distances. This will make it easier for us to determine whether and how dark energy has changed over the course of the universe’s existence.
A powerful pair
The two missions’ surveys will overlap, with Euclid likely observing the whole area Roman will scan. That means scientists will be able to use Roman’s more sensitive and precise data to apply corrections to Euclid’s, and extend the corrections over Euclid’s much larger area.
“Euclid’s first look at the broad region of sky it will survey will inform the science, analysis, and survey approach for Roman’s deeper dive,” said Mike Seiffert, project scientist for the NASA contribution to Euclid at NASA’s Jet Propulsion Laboratory.
“Together, Euclid and Roman will add up to much more than the sum of their parts,” said Yun Wang, a senior research scientist at Caltech/IPAC in Pasadena, California, who has led galaxy clustering science groups for both Euclid and Roman. “Combining their observations will give astronomers a better sense of what’s actually going on in the universe.”
