The Large Magellanic Cloud is encircled by bright, young stars NASA/JPL-Caltech/STScI

An intergalactic scuffle seems to have resulted in the birth of new stars. Astronomers have spotted a large ring of young stars around our galactic neighbour the Large Magellanic Cloud, that probably formed when the Small Magellanic Cloud smashed past its larger sibling.

Located just 160,000 and 200,000 light years away, respectively, the Large and Small Magellanic Clouds are the most luminous of the more than 50 galaxies that orbit the Milky Way. As the clouds revolve around us, they have also orbited each other.

Right now, they are 75,000 light years apart. But they passed close together 200 million years ago. The Small Magellanic Cloud may even have smashed right through its big sibling.


Now Christian Moni Bidin of the Catholic University of the North in Antofagasta, Chile, and his colleagues have spotted what they believe are the glowing remains of this skirmish: six young stars on the fringe of the Large Magellanic Cloud, each part of a vast ring some 80,000 light years in diameter. One star shines between the Magellanic clouds, where young stars were already known, but the other five reside where only older stars had been seen.

“It was surprising,” says Moni Bidin. “There was no indication of recent star formation in this region.”

The young stars at the galaxy’s edge share the same speed as older stars there, indicating the youngsters belong to the galaxy.

“It’s quite an interesting and plausible result,” says David Nidever of the National Optical Astronomy Observatory in Tucson, Arizona.

A collision between the two galaxies would have compressed their gas, making it collapse and spark new stars. The stars are between 10 and 50 million years old, and Nidever says a time lag between the galactic encounter 200 million years ago and the subsequent star birth is reasonable.

Moni Bidin suspects the ring harbours additional young stars. “We studied the tip of the iceberg,” he says: the six stars are all hot, blue, and luminous, making them easy to see. “There could be many fainter stars.”

Journal Reference: Monthly Notices of the Royal Astronomical Society, in press. ArXiv: https://arxiv.org/abs/1612.03072