"I was not looking for the largest spiral - it just came as a gift, " Mr Eufrasio told BBC News.

BBC: Galaxy crash sparks biggest spiral

"It's been known to be among the largest for two decades, but it's much larger than we thought, " explained Mr Eufrasio.

BBC: Galaxy crash sparks biggest spiral

Rafael Eufrasio of the Catholic University of America and Nasa's Goddard Space Flight Center and colleagues from the University of Sao Paulo in Brazil and the European Southern Observatory in Chile were interested in a number of regions away from the galaxy.

BBC: Galaxy crash sparks biggest spiral