Now There's a Map of the Milky Way's "Galactic Atmosphere" 

Researchers at the University of Wisconsin-Madison have created the deepest, most comprehensive survey of the ionized hydrogen that permeates the Milky Way.

To create the map, the group used the Wisconsin H-Alpha Mapper (WHAM), an observatory based in Cerro Tololo, Chile that houses a massive X-ray and ultraviolet light spectrometer that can detect interstellar gas by measuring the light shining between stars. The main mission of WHAM is to figure out where energy produced from stars go?

The project has taken nearly ten years. The completed map is helping scientists understand how the Milky Way has evolved over time. The strip of ionized hydrogen in question is 75,000 light years in diameter and 6,000 light years thick, the entire size of the Milky Way plane. Scientists working on the project believe the strip might play a part in the galaxy’s direction and rotation.

“It’s kind of like a galactic atmosphere,” Matt Haffner, a senior scientist at UWM’s astronomy department and developer of WHAM, said in a news release.

This “atmosphere” plays a huge rule in the life cycle of stars: When stars die, the remaining gas and dust feeds right back into the strip to help form new stars.

A survey image of ionized hydrogen gas in the Milky Way, depicted in red.

WHAM/UW–Madison/Space Science Institute/National Science Foundation

What perplexed Haffner and his team most was how other stars could form thousands of light-years away from the plane. Their best guess is that other larger stars classified as O-types are so large and highly ionized that their emissions are enough to feed new star life throughout the galaxy. (O-type stars are about 15 to 90 times larger than the sun and typically form deep in the galaxy’s plane.) The group hopes this map and WHAM can help further inform other nearby galaxies like the Large and Small Magellanic Clouds.

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