Superfast Stars Have Five-Minute Orbits
Binary pair circle each other at 310 miles a second, study confirms
Two extremely dense stars in an intimate dance are spinning around each other in just 5.4 minutes—making them the fastest known stellar partners in the galaxy, astronomers have confirmed.
To have such a speedy orbit, the stars must be moving at about 310 miles (500 kilometers) a second, the team calculates.
The whirling duo, known as HM Cancri, also has the tightest orbit of any known "binary" star system. (Related: "First Proof 'Tight' Double Suns Can Have Planets.")
Both stars are white dwarfs—the dense, white-hot remnants left behind when sunlike stars die. The stellar corpses are separated by no more than three times the width of Earth.
In such tight
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