2024-01-07 12:00:39
The Small Magellanic Cloud is a galaxy close to the Milky Way and known to scientists, but new research has found that it hides a secret that lies in the fact that it is two galaxies, one behind the other.
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To make this discovery, a team led by Claire Murray, an astronomer at the Space Telescope Science Institute in Maryland, tracked the movement of gas clouds and the young stars being born within them around the Small Magellanic Cloud, located about 199,000 light-years from Earth.
Scientists found that the small galaxy, which is about 18,900 light-years across (or less than one-fifth the width of the Milky Way), contains two distinct star nurseries separated by thousands of light-years.
The Small Magellanic Cloud and the Large Magellanic Cloud are two dwarf galaxies that are gravitationally bound to the Milky Way, and are steadily attracted towards our galaxy with the aim of eventually colliding and merging in the distant future.
While the Large Magellanic Cloud has a disc shape similar to the shape of the Milky Way, the Small Magellanic Cloud is more regular, and the mass of the latter is one-third of the mass of the larger dwarf galaxy, whose mass is equivalent to about 7 billion times the mass of the Sun.
Although the Small Magellanic Cloud was previously thought to be composed of multiple components, it is somewhat obscured by interstellar clouds of gas and dust, meaning it has been difficult to distinguish between these components.
Murray has previously determined that the Small Magellanic Cloud is filled with gas that has been disrupted by gravitational interactions with the Milky Way and the Large Magellanic Cloud.
To investigate the Small Magellanic Cloud, Murray and her colleagues in the study in The Astrophysical Journal amplified radio waves emitted by hydrogen gas in the dwarf galaxy using the Australian Pathfinder Square Kilometer Array, which consists of 36 antenna dishes.
The team followed up these observations using the European Space Agency’s (ESA) Gaia spacecraft, which is currently building a 3D map of the stars in the Milky Way, to track the speed and direction of thousands of younger stars in the Small Magellanic Cloud, which are more than 10 million years old.
Working on the assumption that these young stars were moving in sync with the large gas clouds they generated, scientists observed two distinct patches of gas and dust generating stars.
The two clouds contain different abundances of “metals,” that is, elements heavier than hydrogen or helium, and one cloud appears to be farther from Earth than the other, although the exact separation between them is not yet clear.
One of the mysteries that scientists hope to solve is whether the two objects were held together by gravity or whether one consists of gas that separated from the other through gravitational interactions with the Large Magellanic Cloud.
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