New radio image reveals the true grace of nearby dwarf galaxy

Australia’s new radio telescope has revealed the complexity of the Small Magellanic Cloud’s structure


CSIRO’s ASKAP telescope has mapped the atomic hydrogen gas within the Small Magellanic Cloud. Image credit: ANU/CSIRO

The Small Magellanic Cloud, one of the Milky Way’s orbiting dwarf galaxies, has had its radio emission imaged in unprecedented detail. Astronomers at the Australian National University (ANU) used CSIRO’s new radio telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), to decipher clues as to how the galaxy evolved and what will happen to it in the future.

The new and powerful ASKAP telescope consists of thirty-six 12-metre antennas spanning across the Australian Mid West. By using its innovative radio camera technology, also known as phased array feeds, ASKAP was able to collect large amounts of radio observations from the Small Magellanic Cloud, which appears exclusively in the southern hemisphere.

The Small Magellanic Cloud is tiny in size and mass in comparison to the Milky Way, hence the term ‘dwarf galaxy’. However this neighbouring galaxy appears to have a very complex structure as well. This is likely due to interactions with the Milky Way and it’s galactic companion, the Large Magellanic Cloud, according to Professor Naomi McClure-Griffiths of ANU Research School of Astronomy and Astrophysics.

“The new image captured by CSIRO’s Australian Square Kilometre Array Pathfinder telescope reveals more gas around the edges of the galaxy, indicating a very dynamic past for the Small Magellanic Cloud,” says McClure-Griffiths. “These features are more than three times smaller than we were able to see before and allow us to probe the detailed interaction of the small galaxy and its environment.”

The Small Magellanic Cloud is normally visible with the naked eye in the southern hemisphere. Image credit: NASA/ESA/Hubble Heritage Team (STScl/AURA)

This image was created as part of a survey that aims to investigate galactic evolution. It appears that these distortions to the Small Magellanic Cloud are due to prior interactions with much larger galaxies and internal stellar explosions pushing gas out of the galaxy. It is also in for a very turbulent and unpleasant future.

“The outlook for this dwarf galaxy is not good, as it’s likely to eventually be gobbled up by our Milky Way,” explains McClure-Griffiths. “Together, the Magellanic Clouds are characterised by their distorted structures, a bridge of material that connects them, and an enormous stream of hydrogen gas that trails behind their orbit – a bit like a comet.”

Our neighbouring galaxy has been studied extensively in the recent past by infrared telescope such as NASA’s Spitzer Space Telescope and ESA’s Herschel Telescope. However, infrared only reveals the nature of the dust and stars within the galaxy, whereas ASKAP has been investigating the behaviour of the most ubiquitous gas in the universe, hydrogen.

“The new radio image finally reaches the same level of detail as those infrared images, but on a very different component of the galaxy’s make-up: its hydrogen gas,” says McClure-Griffiths. “Hydrogen is the fundamental building block of all galaxies and shows off the more extended structure of a galaxy than its stars and dust.”

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