Science

Astronomers witness slow death of nearby galaxy

Pictured: The Small Magellanic Cloud viewed from the VISTA telescope. Source: European Southern Observatory (via Flickr)

by Kammy Bogue

The large majority of galaxies in our universe are believed to be not much at all like our own Milky Way, a big spiral galaxy, but instead much smaller objects, known as dwarf galaxies. Their behaviour is usually influenced by larger galaxies that surround them, though they outnumber these larger bodies. In fact, out of the over 30 galaxies that are considered to be part of our local group, there are only two others that are of a similar scale to the Milky Way; the Andromeda and Triangulum galaxies.

Given that these dwarf galaxies make up so much of our universe, we are particularly keen to know more about them, but this is not an easy task. Generally, in astronomy we are restricted in our observations to objects which are relatively bright, that is have reasonably strong emission in some part of the electromagnetic spectrum, with the only exception being gravitational waves. This problem is certainly present for dwarf galaxies, which are not exceptionally luminous, and so we are only able to observe dwarf galaxies that are relatively close.

Another consistent issue that astronomers face are the large timescales over which the events we want to study take place. This is especially true in the case of galactic evolution; a true insight into how galaxies evolve has continually eluded the scientific community and is a hotly debated area of research.

That is why one special dwarf galaxy, the Small Magellanic Cloud (SMC), is an exciting topic at the moment. A peer reviewed study recently published by astronomers from The Australian National University (ANU) and Commonwealth Scientific and Industrial Research Organisation (CSIRO) has been able to view this dwarf galaxy in much more detail than ever before, with some very intriguing results. The SMC is one of two irregular galaxies that interact with the Milky Way, and new observations suggest that its lifetime is currently coming to a close. The new radio images, which provide detail three times finer than the previous images, show evidence of a strong outflow of Hydrogen from the dwarf galaxy. Hydrogen is of course the most abundant element in the universe and is also the key ingredient for forming a star. When the SMC has lost enough gas it will be unable to form any more stars, which is a point of no return for galaxies; it’s ‘death’. For dwarf galaxies it usually means being consumed by their larger neighbours.


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