Apr 9, 2019 - Science

"Cosmic cartography" gets a jump start

This is an image of the whirpool galaxy, which looks purple here with a bright orange and yellow center.

The Whirlpool Galaxy as seen by DESI. Photo: DESI Collaboration

A new telescope instrument saw first light on April 1, a step toward untangling the mystery of dark energy — the invisible, mysterious force thought to drive the expansion of the cosmos.

The big picture: The instrument, called the Dark Energy Spectroscopic Instrument (DESI), is made up of six large lenses that — once fully operational — are expected to help astronomers measure the distances between galaxies in order to clock the expansion of the universe propelled by dark energy.

"DESI is the greatest cosmic cartography experiment we've ever done," Arjun Dey, staff astronomer at the National Optical Astronomy Observatory in Arizona said in a video.

  • "So we're trying to map out where all the galaxies are in the universe out back in time for the last 12 billion years of its history."

DESI's first task was to take a look at the Whirlpool Galaxy, located about 31 million light-years away. This target was chosen as a test to be sure that the lenses were functioning as expected.

How it works: The light taken in by the telescope will be broken up into thousands of colors, allowing scientists to figure out the distances to those galaxies and how quickly they're moving.

  • Astrophysicist Tamara Davis tells Axios that DESI can measure 5,000 galaxies at a time.
  • "By mapping the universe this way, we can measure its expansion rate and how large structures (galaxies and clusters) grow within that expansion. Since these depend on dark energy and dark matter, it means we will be able to measure the properties of the dark components of our universe with unprecedented precision," she says.

What's next: By the end of the year, DESI should be able to measure galactic distances by looking at thousands of light sources instead of just one big picture of the sky.

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