PHILADELPHIA — NASA has nominated three U.S. science teams to participate in the European Space Agency's planned Euclid mission, a space telescope designed to probe the mysteries of dark energy and dark matter and scheduled to launch in 2020.
The University of Pennsylvania’s Gary Bernstein and Bhuvnesh Jain, both professors in the School of Arts and Science’s Department of Physics and Astronomy, are in the ESA-selected group of 43 astronomers who form the largest U.S. team, which is led by the Jet Propulsion Laboratory’s Jason Rhodes.
“The pristine conditions in space will allow Euclid to take pictures with exquisite clarity, which is evident if you’ve seen images from Hubble Space Telescope,” Jain said. “But Euclid can take pictures faster than Hubble and get infrared images which are simply impossible to obtain from the ground.”
Euclid will observe up to 2 billion galaxies occupying more than one-third of the sky with the goal of better understanding the contents of the universe. Despite the seeming preponderance of the stuff, everyday matter makes up only a few percent of everything in the cosmos. The remaining contents are sometimes referred to as the “dark universe,” as it is made up of phenomena that can’t be directly observed.
About 24 percent of the universe consists of dark matter, an invisible substance that does not reflect or emit any light but exerts a gravitational tug on other matter. And the majority of the universe — about 73 percent — is thought to be filled with dark energy. Whereas dark matter pulls on objects through its gravity, dark energy is thought to be a repulsive force pushing matter apart. It is that force that may account for why the expansion of the universe is accelerating, rather than slowing down due to gravity, an observation that earned the Nobel Prize in 2011.
Euclid scientists will use two different methods to make the most precise measurements of the dark universe to date. The first method, called weak lensing, involves analyzing the shapes of billions of galaxies. While dark matter can’t be directly seen, it can distort the light emitted by a galaxy’s stars. The more dark matter between a galaxy and the telescope, the more pronounced the observed distortion will be. By measuring these minute distortions, scientists can understand the amount and distribution of dark matter. Changes in these dark matter structures over time are governed by an interplay between the attractive force of gravity and the repulsive dark energy. Thus, studying galaxy shapes reveals information about both dark matter and dark energy.
Bernstein and Jain have been leaders in the theory and observations of gravitational lensing. Bernstein has been on a number of influential panels reports advising NASA and other agencies on the best course for U.S. research into the dark universe.
Jain is co-leader of the dark energy investigation for the Large Synoptic Survey Telescope, a ground-based project that could be an important complement to the Euclid mission.
Jain and Bernstein also have leadership roles in the Dark Energy Survey, an international collaboration to study the mysterious force using a new imaging system recently installed at an observatory in the Chilean Andes. Euclid will expand upon the Survey’s scope, adding smaller and more distant galaxies that can’t be resolved by ground-based telescopes.
“Looking through the air, you can’t tell whether small galaxies have been distorted or not, because they just look like blurry dots,” Bernstein said. “If one can put a satellite in space and take pictures with it, we’ll be able to add new information from over a billion small, distant galaxies to the analysis.”
Beyond weak gravitational lensing, Euclid will also use a second method, called galaxy clustering or baryon acoustic oscillations, to serve as an independent measurement of dark energy. By making precise measurements of the distances between millions of galaxies, the scientists will be able to chart the expansion of the universe and learn more about the dark energy driving it.
Euclid is a European Space Agency mission with science instruments built by the Euclid Consortium of more than 100 European and international institutions and with participation from NASA. NASA's Euclid Project Office is based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. JPL will contribute the infrared flight detectors for one of Euclid's two science instruments. NASA’s Goddard Space Flight Center in Greenbelt, Md., will perform detailed testing on the infrared flight detectors prior to delivery. Three U.S. science teams, led by JPL, Goddard and the Infrared Processing and Analysis Center at Caltech, will contribute to science planning and data analysis. Caltech manages JPL for NASA.