A Spectroscopic Fingerprint.
Using data from Hubble's Cosmic Origins Spectrograph (COS), the elements that make up 30 Dor #016's stellar winds can be analyzed (top line). By comparing the star's spectrum with a similar star in the nebula (bottom line), astronomers realized 30 Dor #016 must be very young, much like the stars found in the R136 cluster.
By gathering all of this evidence, astronomers are certain that the speedy stellar rogue originated in the R136 cluster. It also seems likely that it was flung out of the cluster by some kind of gravitational interaction with its more massive stellar siblings.
And the drama hasn't finished for 30 Dor #016. Very massive stars live fast and die young and this particular star will explode as a supernova in a few million years time, forming a black hole. It's likely that the black hole will continue flying through the galaxy, eventually getting ejected from the Large Magellanic Cloud all together.
For more details, read "Hubble Spies Trailblazing Star Ripped from Stellar Nursery" on Discovery News.