The Invisible Partner in the Tarantula Nebula
In the Tarantula Nebula, where thousands of stars are born, one bright blue star is behaving strangely. It moves toward us and then away, as if something is tugging it on an invisible string. That 'something' completes an orbit every 17 days, but telescopes can't see it.
Astronomers observed the star 30 times with a spectrograph, which splits light into colors like a prism.