Hunting Dark Energy

Credit: McDonald Observatory

Ever feel like you’re being pushed around? The whole universe knows exactly how you feel. It’s expanding at an ever-increasing rate, pushed apart by some mysterious force that baffled astronomers have dubbed dark energy.

To help pin down what causes the effect, UT Austin astronomers built one of the most advanced astronomical instruments in the world — the Visible Integral-field Replicable Unit Spectrograph (VIRUS). Based at the university’s McDonald Observatory, it’s enabling scientists with the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) to create the largest 3D map of the cosmos ever. By measuring how fast each galaxy is moving away from us, they can determine how the universe’s rate of expansion has changed over the eons, which is key to determining the nature of dark energy. HETDEX’s lead scientist Karl Gebhardt, Herman and Joan Suit Professor in Astrophysics, broke it down for us.

BY THE NUMBERS

2.5 million

Galaxies in the forthcoming cosmic map

32,000

Spectra (rainbows of light) collected with each pointing of the telescope

10 billion light years

Distance to the nearest surveyed galaxies

40%

Amount of survey completed at end of 2020

2023

Expected end of observations