Euclid, an ESA-NASA collaboration, and Nancy Grace Roman Space Telescope will join forces to investigate the accelerated expansion of the universe caused by enigmatic “dark energy.”
In an ambitious mission to unravel the enigma behind the universe’s accelerated expansion, a new space telescope named Euclid, developed by the European Space Agency (ESA) with significant contributions from NASA, is set to launch in July. It will be followed by the Nancy Grace Roman Space Telescope in May 2027. Together, these cutting-edge observatories will embark on an unprecedented exploration of cosmic acceleration, aiming to shed light on the elusive force known as “dark energy.”
“After twenty-five years since its discovery, the accelerated expansion of the universe remains one of the most intriguing mysteries in astrophysics,” remarked Jason Rhodes, senior research scientist at NASA’s Jet Propulsion Laboratory. Rhodes, who serves as the deputy project scientist for Roman and the U.S. science lead for Euclid, added, “With these upcoming telescopes, we will measure dark energy in different ways and with far greater precision than ever before, ushering in a new era of exploration into this cosmic puzzle.”
The nature of the universe’s accelerated expansion poses two primary hypotheses: either an additional energy component is at play, or it signifies a need to revise our understanding of gravity. Euclid and Roman will concurrently investigate both theories, and scientists anticipate that these missions will yield vital insights into the underlying mechanisms of the universe.
Euclid and Roman have been specifically designed to examine cosmic acceleration using distinct and complementary strategies. By constructing 3D maps of the universe, both telescopes aim to address fundamental questions concerning the universe’s structure and history. In combination, their collective power will far surpass the capabilities of each instrument individually.
Euclid’s extensive sky coverage spans approximately 15,000 square degrees, equivalent to about a third of the sky, capturing both infrared and optical wavelengths. Although it provides less intricate details compared to Roman, Euclid will peer back 10 billion years to the early stages of the universe, when it was approximately 3 billion years old.
On the other hand, Roman will conduct a more in-depth exploration over a smaller area, approximately 2,000 square degrees or one-twentieth of the sky, with its superior infrared vision. It will unlock the secrets of the universe at around 2 billion years old, enabling the observation of a larger number of faint galaxies. Roman’s scientific endeavours will extend beyond cosmology to encompass the survey of nearby galaxies, planetary investigations within our own galaxy, the study of celestial objects in the solar system’s outskirts, and more.
The pursuit of dark energy Since its discovery by Belgian astronomer Georges Lemaître in 1927 and later confirmed by Edwin Hubble in 1929, the universe’s expansion has been an ongoing phenomenon. However, scientists initially expected that the gravitational influence of matter would gradually decelerate this expansion. In the 1990s, researchers studying a specific type of supernova made an astonishing observation: approximately 6 billion years ago, dark energy began to exert an increasingly dominant effect on the universe’s evolution. The nature and origins of this dark energy remain shrouded in mystery, creating a fundamental gap in our understanding of the cosmos.
Euclid and Roman will generate distinct streams of valuable data to bridge the gaps in our knowledge. Employing a technique called weak gravitational lensing, both telescopes will investigate the accumulation of matter. This phenomenon occurs when mass warps the fabric of space-time, distorting the appearance of distant sources of light. By analyzing these distortions, Euclid and Roman will each construct a 3D map of dark matter, offering insights into cosmic acceleration. Dark matter’s gravitational pull acts as a cosmic adhesive, counteracting the universe’s expansion and providing valuable clues to understanding the forces at play.
Furthermore, the two missions will explore the clustering of galaxies across different cosmic eras. By examining how galaxies group together, astronomers can trace the expansion history of the universe. This analysis will also facilitate precise gravity tests, enabling scientists to distinguish between modified gravity theories and the presence of an unknown energy component as explanations for cosmic acceleration.
Roman’s additional survey will focus on the discovery of distant type Ia supernovae, a unique class of exploding stars. Since these supernovae exhibit a similar intrinsic brightness, astronomers can determine their distance by measuring their apparent brightness. By comparing the recession velocities of these supernovae at different distances, scientists can trace the cosmic expansion over time, thereby gaining insights into the evolution of dark energy throughout the universe’s history.
In a synergistic collaboration, Euclid and Roman will conduct overlapping surveys, with Euclid likely observing the entire area covered by Roman. This provides an opportunity to employ Roman’s superior sensitivity and precision to refine and enhance the data obtained by Euclid, extending corrections over a significantly larger region.
“The initial observations made by Euclid of the vast sky it will survey will greatly inform the scientific analysis and survey approach of Roman’s more detailed investigation,” explained Mike Seiffert, project scientist for the NASA contribution to Euclid at NASA’s Jet Propulsion Laboratory.
Yun Wang, a senior research scientist at Caltech/IPAC and leader of the galaxy clustering science groups for both Euclid and Roman, emphasized, “Together, Euclid and Roman will exceed the sum of their parts, offering astronomers a more comprehensive understanding of the universe’s inner workings.”
NASA-supported science groups are actively involved in the Euclid mission, contributing expertise and resources. These include the design and fabrication of Euclid’s Near Infrared Spectrometer and Photometer (NISP) instrument sensor-chip electronics by JPL, along with the procurement and delivery of the NISP detectors. Testing of these detectors took place at NASA’s Goddard Space Flight Center. Additionally, the Euclid NASA Science Center at IPAC (ENSCI) will support U.S.-based investigations utilizing Euclid’s data.
For more information about the Euclid mission, visit: https://www.esa.int/Science_Exploration/Space_Science/Euclid/
The Nancy Grace Roman Space Telescope is managed by NASA’s Goddard Space Flight Center, in collaboration with NASA’s Jet Propulsion Laboratory, Caltech/IPAC, the Space Telescope Science Institute, and a science team comprising researchers from various institutions. Major industrial partners include Ball Aerospace and Technologies Corporation, L3Harris Technologies, and Teledyne Scientific & Imaging.
