Colliding galaxies NGC 520. This jumble of stars,gas and dust,known as NGC 520,or Arp 157,is thought to be the remains of two separate disk galaxies that have collided. Because of this NGC 520 has an unusual tail of stars (lower centre) as well as the more usual looking band of dust (diagonal,centre). It lies about 100 million light years from Earth and spans about 100 thousand light years across. The collision started about 300 million years ago and continues today. Image obtained on the night of July 13-14,2005,by the Gemini Multi-Object Spectrograph (GMOS),at the Gemini North Observatory,Hawaii,USA |