Stephan’s Quintet

• wikipedia image
• Édouar Stephan who observed it visually using the 40-cm refractor of the Observatoire de Marseille in 1877.
• 位于飞马座
• 视觉上是五重奏，其实应该是4个星系构成的compact group

NGC 7320 indicates a small redshift (790 km/s) while the other four exhibit large redshifts (near 6600 km/s).

• 类似的著名compact group还有有Seyfert's Sextet(1948)