The Small Magellanic Cloud, one of our closest galactic neighbours, is dying. New observations show that for every sun-sized star that the galaxy forms, it blows away almost ten times as much mass in the form of cold hydrogen gas.
Theories have predicted that dwarf galaxies like the Small Magellanic Cloud (SMC) should be constantly leaking gas, but we have never studied those gas leaks in detail before. Now, Naomi McClure-Griffiths at the Australian National University and her colleagues have used a relatively new radio observatory called the Australian Square Kilometre Array Pathfinder (ASKAP) to see clouds and looping filaments of hydrogen gas blowing out of the nearby galaxy.
鈥淭he SMC is sort of like an extremely volcanic little island, blowing itself apart,鈥� says McClure-Griffiths. 鈥淭he galaxy is literally erupting and we see the enormous gas plumes like the ash plumes from volcanic eruptions.鈥�
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These outflows of gas are caused by massive stars, which can create powerful winds that accelerate the gas away 鈥� and blow off even more gas when they go supernova.
If the SMC continues to lose gas at the rate that it is doing so now, McClure-Griffiths says that within a billion years the galaxy will not have enough gas to form new stars. 鈥淭he SMC will be a pile of old stars, rather than an active star-forming galaxy,鈥� she says. 鈥淚t鈥檚 a sort of slow death.鈥�
As the gas flows out of the SMC, it feeds the Magellanic Stream, a vast river of gas flowing from the SMC and its partner, the Large Magellanic Cloud or LMC, and beneath the Milky Way.
鈥淓ventually that gas is going to fall down onto the Milky Way disk and is going to help produce more stars here,鈥� says David Nidever at Montana State University. 鈥淭he Small Magellanic Cloud鈥檚 loss is our gain.鈥�
The gas isn鈥檛 the only thing that鈥檚 falling into the Milky Way: both the Small and Large Magellanic Clouds are expected to fall into our galaxy in the distant future. The SMC is already starting to interact with the edge of the Milky Way, which may accelerating the gas loss process, says David Law at the Space Telescope Science Institute in Maryland. 鈥淎s it falls deeper into the Milky Way, even the stars will be shredded out of the galaxy,鈥� he says. 鈥淭he gas is just the first casualty.鈥�
Nature Astronomy
