Euclid Mission

Two concepts for Euclid Satellite

Shirley Ho

Rachel Mandelbaum

Carnegie Mellon University astrophysicists Shirley Ho and Rachel Mandelbaum are part of a team tasked with chasing down some of the universe's most mysterious phenomena: dark matter and dark energy. The Euclid mission, to which they have been appointed, is an initiative to build a space-based telescope to better study how dark matter and dark energy manifest themselves.

Ho and Mandelbaum are assistant professors of physics and members of CMU's Bruce and Astrid McWilliams Center for Cosmology. They are among 40 researchers newly selected to join the elite U.S. team that will participate in both building and launching the space-based telescope.

Euclid is part of the European Space Agency (ESA). NASA is working in conjunction with the ESA, and will support the researchers from 2013 to 2028 as they prepare for and carry out collaborative scientific research using the data gathered by Euclid, which is planned for launch in 2020.

Though they make up 95 percent of the matter and energy in the universe, dark matter and dark energy cannot be seen; their presence can only be detected by their effects on things we can see and measure, like stars and galaxies. Euclid would not only be a telescope, but would also be outfitted with imaging and spectroscopic instruments to study the "expansion history" of the universe in various ways. This is where the expertise of Ho and Mandelbaum come into play.

Mandelbaum studies the slight distortions in the images of galaxies through telescopes, which are caused by the gravitational pull of dark matter, called weak gravitational lensing. This type of measurement allows researchers to derive how much dark matter lies between galaxies and how it is distributed throughout space.

"With lensing we can learn about the large scale distribution of all of the matter of the universe — even the dark matter we can't see. If we truly want to understand the structure and evolution of the universe, we need a tool like lensing that reveals the presence of all of the matter," Mandelbaum said.

Ho specializes in redshift space distortions — changes in light wavelength as the object emitting light moves away from the observer — and baryon acoustic oscillations (BAOs), which are essentially echoes of sound waves. These faint reverberations can be measured and used to determine the universe's expansion over time.

Of the capabilities of the mission, Ho said, "Euclid scientists can combine what is learned from these probes to test our understanding of what the universe is made of and how the universe works."