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Star-rich galaxies are polluting the cosmos

Star-rich galaxies are polluting the cosmos
According to a new study, galaxies pump out rather dirty gas exhausts. Photo by James Josephides/Swinburne Astronomical Productions

Aug. 30 (UPI) -- Star factories, like many factories here on Earth, are major polluters, according to a new survey.

Using spectral instruments at Hawaii's W.M. Keck Observatory in Hawaii, researchers measured the gas inflows and outflows from a galaxy about 500 light-years from the Sun.

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The analysis, published Monday in the journal The Astrophysical Journal, showed the gas leaving star-forming galaxies is a lot dirtier than the gas coming in.

To produce new generations of stars, galaxies rely on a steady influx for molecular gas clouds from intergalactic space.

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"On its way in it is made of hydrogen and helium," study co-author Deanne Fisher, associate professor at the Center for Astrophysics and Supercomputing at Swinburne University in Australia, said in a press release.

"By using a new piece of equipment called the Keck Cosmic Web Imager, we were able to confirm that stars made from this fresh gas eventually drive a huge amount of material back out of the system, mainly through supernovas. But this stuff is no longer nice and clean -- it contains lots of other elements, including oxygen, carbon, and iron," Fisher said.

How a galaxy takes in, processes and expels material -- or the rates of accretion and outflow -- dictates a galaxy's mass and growth.

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Until now, scientists have relied on rough estimates of accretion and outflow rates to study this important galactic cycle.

For the new study, researchers used the Keck Cosmic Web Imager to measure the streams of gas flowing into and out of a disk galaxy named Mrk 1486, which is located 500 light-years from Earth.

Because Mrk 1486 lies edge-on in relation to Earth, astronomers were able to easily observe gas flowing in and out of the galactic disk.

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"We found there is a very clear structure to how the gases enter and exit," said Alex Cameron, who recently left the University of Melbourne to work as a postdoctoral research assistant at the University of Oxford.

"Imagine the galaxy is a spinning frisbee. The gas enters relatively unpolluted from the cosmos outside, around the perimeter, and then condenses to form new stars. When those stars later explode, they push out other gas -- now containing these other elements -- through the top and bottom," Cameron said.

The early universe was home to relatively few elements. But each new generation of galaxies and stars generated novel elements.

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Most of the elements on the Periodic Table -- including many that are essential to life on Earth -- are forged by nuclear fusion deep inside a star's core.

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When stars grow old and collapse, they sometimes erupt in a fiery explosion, expelling gas, dust and new elements out into the cosmos. These novel elements become incorporated into stars, planets and asteroids.

"This work is important for astronomers because for the first time we've been able to put limits on the forces that strongly influence how galaxies make stars," said Fisher. "It takes us one step closer to understanding how and why galaxies look the way they do -- and how long they will last."

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