New lenses to help in the hunt for dark energy

March 21, 2016 by Matt Williams, Universe Today

Since the 1990s, scientists have been aware that for the past several billion years, the universe has been expanding at an accelerated rate. They have further hypothesized that some form of invisible energy must be responsible for this, one which makes up 68.3% of the mass-energy of the observable universe. While there is no direct evidence that this "dark energy" exists, plenty of indirect evidence has been obtained by observing the large-scale mass density of the universe and the rate at which is expanding.

But in the coming years, hope to develop technologies and methods that will allow them to see exactly how has influenced the development of the universe. One such effort comes from the U.S. Department of Energy's Lawrence Berkeley National Lab, where scientists are working to develop an instrument that will create a comprehensive 3D map of a third of the universe so that its growth history can be tracked.

Known as the Dark Energy Spectroscopic Instrument (DESI), this project plans to start with the present day, pinpointing the locations of galaxies in the universe, and then work backwards into the past. DESI officially kicked off with the recent delivery of two new and improved lenses to the Mayall Telescope at the Kitt Peak National Observatory in Arizona.

The first of six such upgrades, these two new lenses – Corrector Lens 1 and Corrector Lens 4 (C1 and C4) – have been in production since early 2015. Measuring 1 meter in diameter and weighing 201.395 kg (444 pounds) and 236.775 kg (522 pounds), respectively, these lenses are scheduled to undergo a final antireflective coating before being integrated into the Mayall telescope's new steel corrector barrel.

New lenses to help in the hunt for dark energy
The C4 lens after it arrived at the NOAO. The faces of Gary Poczulp, Ron Probst, Dick Joyce and Ming Liang (project scientists for DESI) are reflected in the lens. Credit: Tim Miller/LBL

Each of these lenses comes equipped with 5000 optical fibers, similar to kind of cables used for high-speed data traffic (i.e. internet and telecommunications). They will give the 4-meter telescope a very wide field of view and be able to detect the light coming from 5000 galaxies at a time. This light will then be directed to the 30 cameras and spectrographs that are connected to the Mayall telescope, which the science team will then measure to gauge its redshift.

For many years, the Berkeley Lab has been measuring the redshift of distant galaxies – the ratio of the wavelength that is seen to the wavelength the light had when it left the galaxy – to gauge their distances from our Solar System. However, since light will stretch exactly the way the universe stretches, these measurements have also been giving the Berkeley scientists an idea of how the universe is expanding.

Once the entire DESI package is assembled – which is expected to happen by 2018 – it will begin collecting spectrographic information on a total of 35 million distant galaxies and quasars. This information will then be used to construct the largest 3D map of the universe, one that spans 10 billion light years. This will allow DESI scientists to not only survey the large-scale structure of the universe, but also look back in time and see how the universe changed over the past 10 billion years.

New lenses to help in the hunt for dark energy
A picture of the Berkeley Lab-developed charge-coupled devices (CCDs), light-sensors that allow the Mosaic-3 camera to capture infrared light from distant galaxies. Credit: Tom Hurteau/Yale University Physics Department

However, redshift alone can only provide astronomers with relative distances. In order to create the 3D map with a genuine sense of scale, the DESI scientists will also be relying on baryon acoustic oscillations – which are periodic fluctuations in the density of the visible baryonic matter of the universe. Together, these measurements of the changing distance between galaxies could show us exactly how dark matter influences cosmic expansion.

DESI is undeniably the next wave of innovation when it comes to how we observe the universe, combing high-performance optics with computer-assisted analysis. And when the map is finally complete, scientists may begin to see exactly how this mysterious energy that permeates our has influenced its expansion and evolution.

Another step on the long, winding road from theory to knowing!

Explore further: How a new telescope will measure the expansion of the universe

Related Stories

New galaxy-hunting sky camera sees redder better

February 2, 2016

A newly upgraded camera that incorporates light sensors developed at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) is now one of the best cameras on the planet for studying outer space ...

Explore galaxies far, far away at internet speeds

January 21, 2016

No need for hyperdrive: Scientists have released an "expansion pack" for a virtual tour of the universe that you can enjoy from the comfort of your own computer. The latest version of the publicly accessible images of the ...

An army of tiny robots that tracks galaxies

September 30, 2015

Why is the universe expanding at an increasing rate? Scientists will attempt to gain a better understanding of this phenomenon by mapping the distribution of galaxies in the universe. Astrophysicists and robotics engineers ...

Recommended for you

STEREO—10 years of revolutionary solar views

October 26, 2016

Launched 10 years ago, on Oct. 25, 2006, the twin spacecraft of NASA's STEREO mission – short for Solar and Terrestrial Relations Observatory – have given us unprecedented views of the sun, including the first-ever simultaneous ...

Image: Changing colors in Saturn's pole

October 26, 2016

These two natural color images from NASA's Cassini spacecraft show the changing appearance of Saturn's north polar region between 2012 and 2016.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.