The Milky Way is not the only galaxy in the universe. But as it was quietly orbiting, it somehow captured smaller galaxies, and the two largest of these galaxies are now known as the Small and Large Magellanic Clouds. These twin dusty smears are visible in the Southern Hemisphere of Earth. The Magellanic Stream, an enormous stream of gases, was released over billions of years ago.
Now, the Magellanic Stream stretches across more than half of the night sky, which baffles scientists as the stream has become a billion times more massive than the Sun.
Astronomers from the University of Wisconsin-Madison discovered that Magellanic Clouds are surrounded by a halo of warm gas that acts as a protective layer to it shielding them from the Milky Way’s own halos, which then adds to most of the Magellanic Stream.
The study, published on September 9 in the journal Nature, found that parts of the Milky Way’s halo dispersed and stretched to form the Magellanic Stream as the smaller galaxies entered the influence of the Milky Way.
The first author of the study and graduate student in the UW-Madison physics department, Scott Lucchini, said that the existing models about the Magellanic Stream are outdated because experts cannot account for its mass. Due to that, their team came up with a novel solution that best explains the mass of the stream, said astronomy professor Elena D’Onghia from UW-Madison.
Together with physicists and astronomers from the UW-Madison, the Space Telescope Science Institute in Baltimore, and the University of Sydney, D’Onghia completed the work when she was a scholar at the Center for Computation Astrophysics of Flatiron Institute in New York City.
According to older models of the Magellanic Streams, they are formed due to the gravitational tides and forces of the galaxies pushing against each other as the Magellanic Clouds came into orbit around the Milky Way galaxy. However, this model is rendered outdated as it can only explain the size and shape of the stream and only accounted for just a tenth of its mass.
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In a new simulation of the formation of the Magellanic Stream created by Lucchini, it explains that the formation of the streams is divided into two periods.
First, the Large Magellanic Cloud stripped away its gas from its smaller partner over a billion years ago while the two galaxies were far away from the Milky Way. Ultimately, this stolen gas made up 10 to 20 percent of the stream’s mass.
Later, the corona of the galaxies gave up a fifth of its mass as it fell into the Milky Way, which forms the stream stretching across the sky by interactions between its corona and the Milky Way’s gravity.
This new model is the first to fully explain the full mass of the Magellanic Stream and why it lacks stars as it adapted its filamentous stream.
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Milky Way, Magellanic Stream, Magellanic Clouds, Large Magellanic Cloud, Star, Galaxy
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