The cosmos is a dark, spooky place. More so when you realize that most of the matter in it actually lurks in voids.
If there was a dark alley in space, it would be the intergalactic medium (IGM)—the cold, diffuse gas that inhabits these shadows between galaxies and emits almost zero light. No human brain can even begin to grasp in what dead zone you would find yourself by following it to the end (if it even has one).
NASA is finally going to illuminate at least some of what lies in the IGM, even if the space agency won’t literally be shining a flashlight on it. The space agency just blasted a sounding rocket that uses ultraviolet optics, aka the Dual-channel Extreme Ultraviolet Continuum Experiment (DEUCE) into space to investigate the mysteries out there. Ultraviolet starlight from star-forming galaxies is thought by many scientists to be what ionized the universe. Unfortunately, this UV radiation cannot be studied from Earth because it is blocked by our atmosphere, so something needs to capture it from above our planet. Sounding rockets like DEUCE can zero in on it without putting the same dent in NASA’s budget as space telescopes like Hubble.
“DEUCE is about being able to better understand if and how star-forming galaxies ionized the early universe,” said researcher Nicholas Erickson, a graduate student who is also a collaborator on the mission. “This ionizing light has never been measured accurately in hot stars, and DEUCE will make the first calibrated measurement of it, telling us the contribution stars could have had to helping ionize the universe.”
The rocket has just taken off to its first destination, star Beta Canis Major, and will be exploring Epsilon Canis Major this December. These stars are young (around 12 and 23 million years old is nothing in star terms) and blazing hot. They are also close enough to Earth for their light to touch down on our planet before interstellar gas devours it, which is important for scientists who are looking to measure it to see if there is enough radiation there to prove that the IGM contains a significant amount of starlight. DEUCE will use the largest microchannel plate detector ever launched into space to make this measurement. Not that it’s going to be easy.
“It's a hard measurement to make, because there still is neutral hydrogen between stars that is extremely effective at absorbing the starlight at these wavelengths,” Erickson admitted.
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