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How James Webb is peering into galaxies to see stars being born

Georgina Torbet
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Recently astronomers used the James Webb Space Telescope to look at the structures of dust and gas which create stars in nearby galaxies. Now, some of the researchers have shared more about the findings and what they mean for our understanding of how galaxies form and evolve.

The project, called Physics at High Angular resolution in Nearby Galaxies, or PHANGS, used James Webb to observe several galaxies which are similar to our own Milky Way to see how stars are forming within them.

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“We’re studying 19 of our closest analogues to our own galaxy,” explained one of the researchers, Erik Rosolowsky of the University of Alberta, in a statement. “In our own galaxy, we can’t make a lot of these discoveries because we’re stuck inside it.”

By using Webb’s infrared instruments, the researchers can look through clouds of dust and gas which could be opaque if viewed in the visible light range. As objects get warmer, they give off more infrared light, so Webb’s instruments can see where pockets of warmer dust and gas sit, and how this relates to areas where stars are forming.

“At 21 micrometers [the infrared wavelength used for the images collected], if you look at a galaxy you will see all of those dust grains heated with light from the stars,” said Hamid Hassani, another of the researchers. “The infrared light is really key to tracing the cold and distant universe.”

The team has so far examined 15 galaxies, out of a total of 19 that they will examine for their project. For the galaxies imaged so far, the researchers took information about the distribution and warmth of stars and worked out the ages of those stars. That came with some surprises, as many of the images they were observing showed bright stars that were younger than they were expecting.

“The age of these [stellar] populations is very young. They’re really just starting to produce new stars and they are really active in the formation of stars,” said  Hassani.

It is the process of star formation which makes a galaxy grow and thrive. Star formation is a delicate balance of having enough material for new stars to form, and the stellar winds created by young stars blow this material away.

“If you have a star forming, that galaxy is still active,” Hassani said. “You have a lot of dust and gas and all of these emissions from the galaxy that trigger the next generation of the next massive star forming and just keep the galaxy alive.”

The research is published in The Astrophysical Journal Letters.

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