The late autumn sky brings into view two popular open star clusters located about halfway between the constellations Perseus and Cassiopeia. The famous double star cluster in Perseus is well placed for observation near midnight this week. Viewed in a dark sky, these celestial treasures appear as one large, hazy patch about the size of two full moons. But with binoculars or a telescope, you’ll discern hundreds of glittering stars. The majority are blazing hot blue-white super giants, but sprinkled through the field of vision are the yellow and orange of smaller, cooler stars.

Unlike the dense populations of globular star clusters, open star clusters travel through the cosmos loosely gravitationally bound to one another. We perceive the luminous individual stars as gems strewn against the black velvet of space. NGC 869 and NGC 884, as they are formally named, have been acknowledged since ancient times and often appear in Perseus’ story as the jeweled handle of his sword.

Although they are over 7,000 light years away from us, in the adjacent Perseus spiral arm of the Milky Way Galaxy, their distance from each other is only a few hundred light years. And were they as close to us as the more famous open star cluster, the Pleiades, nearly a quarter of our northern sky would be filled with their brilliant stars.

First Published: October 26, 2021, 10:00 a.m.