spaceSpace and Physics

Two Nearby Galaxies Are Locked In A "David vs Goliath" Fight To The Death


Jonathan O'Callaghan

Senior Staff Writer

The SMC (left) and LMC, seen by NASA's Swift satellite. Axel Mellinger, Central Michigan University

Astronomers have found that two of our neighboring dwarf galaxies are locked in a heated battle, continuously landing blows on each other as they fight for survival.

The study, published in the Astrophysical Journal Letters and led by The Australian National University (ANU), found that the nearby Large and Small Magellanic Clouds (LMC and SMC), both of which are visible to the naked eye in the Southern Hemisphere, have been ripping chunks from each other for billions of years.


“This fight is a lot like the one that David and Goliath could have had if the little guy didn’t have such good luck with his slingshot,” said Dr Dougal Mackey from the ANU, the study’s lead author, in a statement.

The researchers found that the distribution of stars of different ages in the SMC suggested it had had numerous interactions with the LMC over billions of years. Parts of the SMC were found to be being either pushed towards or pushed away from the SMC.

However, the LMC has not escaped unscathed either, noted Dr Mackey. He said that the parts of it that were closest to the SMC were “heavily warped and pruned,” while other parts also showed signs of “major distortions.”

The team made their discovery using the Dark Energy Camera on the Blanco telescope in Chile. They found that much of the material was being flung into the region between the two dwarf galaxies, which is known as the Magellanic Stream.

A map of the SMC and LMC, and their interactions. Dougal Mackey/ANU

It was also discovered that an even smaller galaxy, called Hydrus 1, was located within this bridge between the SMC And LMC. It’s only about 326 light-years across, relatively tiny compared to our Milky Way, which is 100,000 light-years across. The LMC and SMC, for comparison, are about 14,000 and 7,000 light-years across, respectively.

“This galaxy is part of a class known as ultra-faint dwarfs, the existence of which was only discovered about 10 years ago,” said Dr Mackey. “These are extremely low-brightness dwarf galaxies, but they still have lots of dark matter.”

Ultimately, both the LMC and SMC will be eaten by the Milky Way, possibly in a few hundred million years. Until then, it looks like these two competitors will continue to land blows on each other, as they fight for supremacy on the cosmic battlefield.

Another recent study, using data from ESA's Gaia telescope, also found evidence for a recent collision between the two galaxies. Unfortunately for the SMC, however, it doesn’t look like it’s faring quite as well as David in this latest battle.


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