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Friday, November 18, 2011

The Galaxy Has Been Doing Recycling

two galaxies
Recycling process does not only happen in everyday human life. Recycle the waste into a new tool is a new knowledge for mankind. But in fact, galaxies have been doing it far longer than human life on earth. NASA through the Hubble telescope has been observing the behavior of galaxies that recycle large volumes of hydrogen and heavy elements. In this way, a galaxy can form new stars to life for billions of years.

This conclusion is based on a series of Hubble Space Telescope observations that flexed the special capabilities of its Cosmic Origins Spectrograph (COS) to detect gas in the halo of our Milky Way and more than 40 other galaxies. Data from large ground-based telescopes in Hawaii, Arizona and Chile also contributed to the studies by measuring the properties of the galaxies. Astronomers believe that the color and shape of a galaxy is largely controlled by gas flowing through an extended halo around it. The three studies investigated different aspects of the gas-recycling phenomenon.

From the observation in mind, a large mass of clouds that fall through the halo giants our Milky Way galaxy, triggering star formation ongoing. These clouds originate from hot hydrogen gas is 20 000 light years from the Milky Way disk and contains enough material to produce 100 million solar. Some of this gas is recycled continuously replenished by star formation, energy of nova and supernova explosions, the chemically enriched gas kicks back into the halo.

Researchers also found that this gas is nearly absent from galaxies that have stopped forming stars. In these galaxies, the “recycling” process ignites a rapid firestorm of star birth which can blow away the remaining fuel, essentially turning off further star-birth activity. This is evidence that gas pushed out of a galaxy, rather than pulled in from intergalactic space, determine a galaxy's fate."

Galaxies are forming stars very rapidly, perhaps a hundred solar masses per year, could push two million-degree gas that is very far into intergalactic space at speeds of up to two million miles per hour. That's fast enough for gas to escape forever and never refuel the parent galaxy.

While hot gas "winds" from galaxies have been known for some time, the new COS observations reveal that hot outflows extend to much greater distances than previously thought and can carry a tremendous amount of mass out of a galaxy. Some of the hot gas is moving more slowly and could eventually be recycled. The observations show how gas-rich star-forming spiral galaxies can evolve to elliptical galaxies that no longer have star formation.

The light emitted by this hot plasma is invisible, so the researchers used COS to detect the presence of the gas by the way it absorbs certain colors of light from background quasars. Quasars are the brightest objects in the universe and are the brilliant cores of active galaxies that contain active central black holes. The quasars serve as distant lighthouse beacons that shine through the gas-rich "fog" of hot plasma encircling galaxies. At ultraviolet wavelengths, COS is sensitive to the presence of heavy elements, such as nitrogen, oxygen, and neon. COS's high sensitivity allows many galaxies to be studied that happen to lie in front of the much more distant quasars. The ionized heavy elements are markers for estimating how much mass is in a galaxy's halo.

Source: NASA

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