Galaxies launch heavy elements into deep space and run out of raw materials needed to build stars and planets.
Galaxies are filled with star-forming material. Cosmic dust and gas flowing inside intergalactic spaces give birth to a new generation of stars. But recent research has found that galaxies waste a lot of star forming material too. They eject the heavy elements generated during star the formation process to a million light years away into the surrounding halos and deep space. That is how galaxies run out of ingredients needed for building stars and planets.
“Previously, we thought that these heavier elements would be recycled into future generations of stars and contribute to building planetary systems,” said lead researcher Benjamin Oppenheimer from Center for Astrophysics & Space Astronomy said. “As it turns out, galaxies aren’t very good at recycling.”
The reservoir of gas around a galaxy is known as circumgalactic mediumand it is something where large scale inflow and outflow from galaxies take place. Circumgalactic medium is thought to shape galaxies and drive their evolution.
To study the composition of circumgalactic medium or CGM, researchers used observational data from Cosmic Origin Spectrograph (COS). COS is an instrument that is installed on Hubble Space Telescope and uses ultraviolent spectroscopy to investigate the evolution of universe.
Usually spiral galaxies produce stars at exceptionally high rate such as our own galaxy Milky Way heavily form stars and have a bluish color while the red colored elliptical galaxies have a very low star formation rate. But both types of galaxies are enriched with hundreds of billions of stars, meaning they also create heavy elements in abundance. When researchers observed the data, they found that more than half of galaxy’s heavier elements were found outside of galaxies in the CGMs rather than existing within the galaxies themselves. The findings suggest that galaxies may not be as good as retaining their raw material as we thought previously.
Researchers found that the CGM of elliptical galaxies was hotter compared to those of spiral galaxies, topping over one million degrees Kelvin in elliptical ones and reducing the fraction of highly ionized oxygen. The observations were not possible without COS instrument that breaks light into colors and measure the intensity of each color, enabling scientists to learn about the light emitting from the object with pinpoint precision.
“It takes massive amount of energy from exploding supernovae and supermassive black holes to launch all these heavy elements into the CGM,” said Oppenheimer. “This is violent and long-lasting process that can take over 10 billion years, which means that in a galaxy like Milky Way, this highly ionized oxygen we’re observing has been there since before the Sun was born.”
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