In case you didn’t know, a huge – like, on a galactic scale – cloud of gas is now speeding toward our galaxy at 700,000 miles per hour. Other theories maintain that Smith Cloud originated inside the galaxy.
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It was discovered in 1963 by Gail Bieger, who was an astronomy student at Leiden University in the Netherlands at the time. In around 30 million years, the cloud will collide with the galaxy – a long time in human years, but a relatively short period in cosmic terms.
“It’s telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another”. Some thought that the cloud could be a starless galaxy or just a giant body of gas, falling in to the Milky Way from intergalactic space.
Scientists used the Hubble Space Telescope to measure its chemical composition. The gas cloud eerily shaped as a comet stretches 11,000 light-years in length and about 2,500 light-years in width.
In particularly they found it was as rich in sulphur atoms as the Milky Way’s outer disk, which lies around 15,000 light years from our own solar system.
Since astronomers discovered the Smith Cloud, a giant gas cloud plummeting toward the Milky Way, they have been unable to determine its composition, which would hold clues as to its origin. If the cloud were viewable in visible light, it would be 30 times greater than the size of the full moon in the night sky. It’s since been repeatedly observed in radio wavelengths with the NRAO’s Green Bank Observatory in West Virginia and recently with the Hubble Space Telescope, which determined that it does in fact contain heavy elements like sulfur (contrary to some earlier analyses).
A vast formation of hydrogen gas is heading toward the Milky Way galaxy, astronomers from the Hubble Space Telescope say, but it won’t reach our galaxy for about 30 million years. If either of these scenarios proved true, the cloud would contain mainly hydrogen and helium, not the heavier elements made by stars.
Astronomers are now trying to find out how Smith Cloud get to the location it is now and what catastrophic event could have hurled it from the Milky Way’s disk, and how it remained intact. This would not happen if it were pristine hydrogen from outside the galaxy. Could it be a region of dark matter – an invisible form of matter – that passed through the disk and captured Milky Way gas?
The team’s research appears in the January 1, 2016, issue of The Astrophysical Journal Letters.
The Smith Cloud is classified as a high-velocity cloud due to the high speed at which it’s now orbiting the Milky Way.
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But new measurements taken with the Hubble Space Telescope tell a different story.
