ONE OF THE CLOSEST GALAXIES TO THE MILKY WAY MAY BE HIDING A SECOND GALAXY

New observations of the Small Magellanic Cloud show that it might actually be two galaxies disguised as one

The Small Magellanic Cloud (SMC) is a nearby galaxy that’s very familiar to astronomers, or so they thought. New research suggests that the satellite galaxy of the Milky Way, located around 199,000 light years from Earth, seems to have been hiding a secret – it’s actually two galaxies, one behind the other. To make the discovery, a team led by Claire Murray, an astronomer at the Space Telescope Science Institute in Maryland, tracked the movement of gas clouds and young stars being born within them around the SMC. They found that the small galaxy, which is around 18,900 light years wide – less than one-fifth the width of the Milky Way – contains two distinct stellar nurseries thousands of light years apart. Both the SMC and the Large Magellanic Cloud (LMC) are dwarf galaxies that are gravitationally bound to the Milky Way and are being steadily drawn towards our galaxy for a collision and merger in the far future.

While the LMC exhibits a disc-like shape similar to that of the Milky Way, the SMC is more irregular.

The SMC has only one-third the mass of the larger dwarf galaxy, which has a mass equivalent to around 7 billion times that of the Sun. Although the SMC was previously thought to consist of multiple

The SMC and LMC alongside the Milky Way components, it’s somewhat obscured by interstellar clouds of gas and dust, meaning these features have been hard to distinguish.

Murray has previously determined that the SMC is a ‘train wreck’ of a dwarf galaxy, full of gas disrupted by gravitational interactions with the Milky Way and the Large Magellanic Cloud. For the new investigation of the SMC, Murray and her colleagues zoomed in on radio waves emitted by hydrogen gas in the dwarf galaxy using the Australian Square Kilometre Array Pathfinder radio telescope, which comprises 36 dish antennae. The team followed up these observations by using the European Space Agency’s (ESA) Gaia spacecraft, which is currently building a 3D map of stars in the Milky Way, to track the speed and direction of thousands of stars in the Small Magellanic Cloud that are younger than 10 million years old.

Working with the assumption that these young stars are moving in conjunction with the large clouds of gas that birthed them, the researchers spotted two distinct star-birthing patches of gas and dust. The two clouds have different abundances of metals, meaning elements heavier than hydrogen or helium, and one cloud seems to be more distant from Earth than the other, though their exact separation isn’t yet clear.