The article said:

For Hubble's electronic cameras, cosmic rays skimming along the detector look like "scratches." But once spectroscopy was done on the oddball streak van Dokkum realized it was really a 200,000-light-year-long chain of young blue stars located over halfway across the universe! van Dokkum and his colleagues believe that it stretches between a runaway monster back hole and the galaxy it was ejected from. The black hole must be compressing gas along its wake, which condenses to form stars. Nothing like it has ever been seen anywhere else in the universe before.