The galaxy next to ours is being torn apart, study suggests

‘When we first got this result, we suspected that there might be an error,’ scientist says

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The galaxy next to ours might be getting torn apart, a study has suggested.

The Small Magellanic Cloud, or SMC – a relatively small galaxy that neighbours ours – appears to be getting torn to bits by the gravitational pull of a neighbouring galaxy, the new research suggests.

“When we first got this result, we suspected that there might be an error in our method of analysis,” said Kengo Tachihara, from Nagoya University in Japan. “However, upon closer examination, the results are indisputable, and we were surprised.”

The SMC is one of our nearest neighbours, which allows researchers to keep close tabs on the roughly 7,000 massive stars that make up the galaxy. Those stars are more than eight times the mass of our Sun, and usually last for just a few million years before they explode into supernovae.

As they watched those stars, researchers noticed that they appeared to be getting pulled apart by the Large Magellanic Cloud, or LMC, which itself neighbours the galaxy.

“The stars in the SMC were moving in opposite directions on either side of the galaxy, as though they are being pulled apart,” said Tachihara. “Some of these stars are approaching the LMC, while others are moving away from it, suggesting the gravitational influence of the larger galaxy.

“This unexpected movement supports the hypothesis that the SMC is being disrupted by the LMC, leading to its gradual destruction.”

Researchers also noticed that the SMC does not appear to be rotating. Usually, young massive stars move around along with the gas that they were born from – but the SMC’s stars do not appear to be moving in that way, suggesting that the gas itself is not rotating as expected.

That could lead to a new understanding not only of the SMC but also the way it interacts with galaxies including our own.

Further the research could help us better understand the conditions and story of the early universe. The SMC is useful for understanding the cosmos when it was younger than it is today, because it shares some characteristics with early galaxies.

“We are unable to get a ‘bird's-eye view’ of the galaxy in which we live,” said Tachihara. “As a result, the SMC and the LMC are the only galaxies in which we can observe the details of stellar motion. This research is important because it allows us to study the process of star formation in connection with the motion of stars throughout the galaxy.”

The work is described in a new paper, ‘Evidence of Galactic Interaction in the Small Magellanic Cloud Probed by Gaia-selected Massive Star Candidates’, published in The Astrophysical Journal Supplement Series.