The Nicholas U. Mayall Telescope that was made operational forty-five years ago has been entrusted with a new task – solving the dark energy mystery.
The telescope has been given the job of creating the largest 3-D map of the universe that astronomers intend to use to solve dark energy mystery thereby finding answers to some of the most puzzling questions including secrets behind accelerating expansion of the universe.
The telescope is currently going the largest overhaul in the telescope’s history. The telescope will be fitted with Dark Energy Spectroscopic Instrument (DESI), which has seen involvement from more than 465 researchers from about 71 institutions. DESI will use an array of 5,000 swiveling robots, each carefully choreographed to point a fiber-optic cable at a preprogrammed sequence of deep-space objects, including millions of galaxies and quasars, which are galaxies that harbor massive, actively feeding black holes.
The fiber-optic cables will carry the light from these objects to 10 spectrographs, which are tools that will measure the properties of this light and help to pinpoint the objects’ distance and the rate at which they are moving away from us. DESI’s observations will provide a deep look into the early universe, up to about 11 billion years ago.
The cylindrical, fiber-toting robots, which will be embedded in a rounded metal unit called a focal plane, will reposition to capture a new exposure of the sky roughly every 20 minutes. The focal plane, which is now being assembled at Berkeley Lab, is expected to be completed and delivered to Kitt Peak this year.
DESI will scan one-third of the sky and will capture about 10 times more data than a predecessor survey, the Baryon Oscillation Spectroscopic Survey (BOSS). That project relied on a manually rotated sequence of metal plates – with fibers plugged by hand into pre-drilled holes – to target objects.
All of DESI’s six lenses, each about a meter in diameter, are complete. They will be carefully stacked and aligned in a steel support structure and will ultimately ride with the focal plane atop the telescope.
Each of these lenses took shape from large blocks of glass. They have criss-crossed the globe to receive various treatments, including grinding, polishing, and coatings. It took about 3.5 years to produce each of the lenses, which now reside at University College London in the U.K. and will be shipped to the DESI site this spring.
As part of the overhaul, the entire top end of the telescope will be removed and replaced with DESI instruments. A large crane will lift the telescope’s top end through the observing slit in its dome.
Besides providing new insights about the universe’s expansion and large-scale structure, DESI will also help to set limits on theories related to gravity and the formative stages of the universe, and could even provide new mass measurements for a variety of elusive yet abundant subatomic particles called neutrinos.
Some of the achievements of the Mayall Telescope include carrying out of measurements supporting the discovery of dark energy and establishing the role of dark matter in the universe from measurements of galaxy rotation. Observations from the telescope has helped determine the scale and structure of the universe.
It was one of the world’s largest optical telescopes at the time it was built, and because of its sturdy construction it is perfectly suited to carry the new 9-ton instrument.
The expansion of the telescope’s field-of-view will allow DESI to map out about one-third of the sky.