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Sci Tech
Galactic turbulence
IN A huge river of primordial hydrogen flowing from the neighbouring Magellanic Clouds into our Milky Way galaxy, astronomers have discovered evidence of turbulence and concluded that the invisible, hot mass of gas surrounding our galaxy is much thicker than physicists previously thought.
What causes turbulence in a star-free cosmic stream is unclear, but this finding could be important in understanding the cosmic-cloud and star-formation processes, says Snezana Stanimirovic, an astronomer at National Astronomy and Ionosphere Centre at Arecibo, Puerto Rico.
The large Magellanic cloud and the small Magellanic cloud are the Milky Way galaxy's closest galactic neighbours. Like the Milky Way, the Magellanic Clouds contain millions of stars and possibly planets.
The Magellanic Stream runs through the Magellanic Clouds and into the Milky Way. Ultra-rich in hydrogen gas and surrounded by very hot (about 1 million degrees Kelvin) gas from the Milky Way's Galactic Halo, the Magellanic Stream is thought to be about 160,000 light years long. This means that it would take 160,000 years, travelling at the speed of light — to go from one end of the stream to the other.
Using the radio telescope at Arecibo, astronomers have made rare, direct observations of the Magellanic Stream, which dips into the Galactic Halo, a thin veil of gas surrounding the Milky Way that is visible only through the radio spectrum.
Only the Magellanic Stream's northern portion can be seen by the Arecibo Observatory. The astronomers analyzed the hydrogen emission from the stream sections accessible to the Northern Hemisphere and found numerous cometlike clumps and filaments of gas, suggesting turmoil in the stream.
While the Magellanic Clouds are quite visible from Earth's Southern Hemisphere, the Magellanic Stream virtually invisible to the naked eye- can be observed only through radio telescopes from the Southern Hemisphere and from tropical regions of the Northern Hemisphere.
Observers in those regions, without telescopes, can see the large Magellanic cloud at about zero magnitude, which is bright.
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