A 3-D sky-mapping project by Moore Foundation grantees at Lawrence Berkeley National Laboratory that will measure the light of millions of galaxies has received formal approval from the U.S. Department of Energy to move forward with construction.
Installation of the project, called DESI (Dark Energy Spectroscopic Instrument), is set to begin next year at the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz., with observations starting up in January 2019.
DESI will provide a more detailed look at the patterned clustering of visible matter in the night sky across a larger range of distances. This clustering was set in motion by a cooling process in the early universe that produced sound wave-like oscillations through a combination of pressure and gravitational forces.
DESI will also provide a more precise measure of how the universe has spread out over time, and help us understand galaxy evolution and dark matter, which is invisible but inferred from its gravitational effects on normal matter.
This latest DOE approval step, known as Critical Decision 3, triggers spending for major components of the project, including the remainder of the 5,000 finger-width, 10-inch-long cylindrical robots that will precisely point the fiber-optic cables to gather the light from a chosen set of galaxies, stars, and brilliant objects called quasars. The spending will also be used to complete the set of 10 fiber-fed spectrographs that will precisely measure different wavelengths of incoming light.
This light will tell us about the properties of the galaxies, stars, and quasars, and most importantly, how quickly they are moving away from us -- light from objects that are moving away from us is shifted to redder wavelengths ("redshift"). These details can help us learn more about the nature of dark energy that is driving the accelerating expansion of the universe. DESI's observations will provide a deep look back in time, up to about 11 billion years ago.
"We're very excited -- ecstatic -- that we've gotten to this step," said DESI director Michael Levi of Lawrence Berkeley National Laboratory's Physics Division.
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