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Binary star ‘odd couple’ spotted by ALMA

16 Dec 2018, 16:22 UTC
Binary star ‘odd couple’ spotted by ALMA
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An artist’s impression of a binary star system featuring a huge 80-solar-mass sun and a tiny companion star that formed after the original protoplanetary disc fragmented. Image: J. D. Ilee / University of Leeds
The Atacama Large Millimeter/submillimeter Array has spotted two stars forming in the same protoplanetary disc 11,000 light years from Earth. But they are far from identical twins.
On star is huge by even stellar standards, 40 times more massive than the Sun. The other is just one-eightieth that size, indicating a very different history. The larger star, known as MM 1a, formed by traditional means when a dense cloud of gas collapsed under its own gravity, triggering fusion reactions in the high-density, high-temperature core.
But at some point, a portion of the swirling disc apparently broke away, or fragmented, forming the core of the diminutive companion.
“Astronomers have known for a long time that most massive stars orbit one or more other stars as partners in a compact system, but how they got there has been a topic of conjecture,” said Crystal Brogan, an astronomer with the National Radio Astronomy Observatory in Charlottesville, Virginia. “With ALMA, we now have evidence that the disc of gas and ...

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