BBC Science Focus looks up at the heavens and sees two nearby galaxies — the Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC) — that, instead of peacefully spinning in cosmic circles, are apparently whipping into each other like universal buzzsaws:
And what the researchers found was striking. This once-cordial cosmic neighbour is being rather rudely torn apart by the gravity of the Large Magellanic Cloud (LMC) – another nearby dwarf galaxy that’s slightly larger and apparently not above throwing its weight around.
“The SMC is an interacting galaxy, gravitationally bound to the LMC,” Satoya Nakano, the study’s first author, told BBC Science Focus. “The stars on the side of the SMC closer to the LMC are experiencing a stronger gravitational force and are moving towards the LMC, while the stars farther away experience a weaker pull.”
This gravitational tug-of-war – along with a possible nudge from our own Milky Way, which looms some 200,000 light-years away – is slowly pulling the SMC apart.
So, why does this matter?
For one, the team discovered that the SMC isn’t rotating the way astronomers had assumed. Spiral galaxies like our own typically rotate, with stars and gas processing around a central axis. But not all galaxies do – and the SMC, it turns out, might be one of them.
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The lack of rotation doesn’t just change our understanding of the SMC’s structure – it could also throw off estimates of its mass.
“Because the SMC is not rotating, our past estimates of its mass could be wrong,” Prof Kengo Tachihara, another of the study’s authors, told BBC Science Focus.
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You can read more of Nakana’s and Tachihara’s study here, in The Astrophysical Journal’s Supplement Series.