Hypervelocity binary star puzzles astronomers

PB 3877 is a hypervelocity binary star that races through the outer edges of our galaxy. The origin of this star is a puzzle for researchers. The image shows its current location in relation to the position of our sun. (Image: Thorsten Brand)

A traveller from a distant galaxy

Could the star with the cryptic name PB 3877 be an intruder from a distant galaxy? FAU astronomers who – in collaboration with colleagues at the California Institute of Technology (USA) – discovered the star and have observed it closely for year think this may be the case. However, it is not just the origin of the star that is puzzling to the researchers.

PB 3877 races through the outer edge of our galaxy at around around two million kilometres per hour – fast enough, the researchers believe, to overcome the gravitational pull of the Milky Way and leave the galaxy. It is one of the approximately two dozen hypervelocity stars that are currently known.

Does PB 3877 come from another galaxy?

The animation below by Thorsten Brand, a research associate at the Institute of Astronomy, shows the possible paths the binary star PB 3877 may have taken to reach its current position. Does it come from a different galaxy at the edge of the Milky Way or was it catapulted out from the centre of our galaxy?