M45 Pleiades (Seven Sisters)

is one of the most iconic DSO targets — a young open cluster dominated by hot B‑type stars embedded in a blue reflection nebula. The distance is about 444–445 light‑years, the total brightness ~1.6 mag, and the apparent size ~2° (~4 Moons). It sits in Taurus, best observed from late autumn to winter.

The cluster is dominated by hot blue and luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars were once thought to be left over material from the formation of the cluster, but are now considered likely to be an unrelated dust cloud in the interstellar medium through which the stars are currently passing.

Object: key facts

• RA/Dec (J2000): ~03h 47m, +24° 07′ (Taurus).
• Distance: ~444–445 ly (Gaia/HST; literature varies slightly).
• Age: ~100 Myr (range 75–150 Myr depending on method).
• Size & mag: ~2° across; ~1.6 mag.
• Reflection nebulae: NGC 1432 (Maia) and NGC 1435 (Merope); the dust is unrelated to the cluster’s formation — the stars are passing through an interstellar cloud.
• Evolution: the cluster will disperse in ~250 Myr due to galactic interactions.

 

New research (2025): Using TESS + Gaia, astronomers identified a Greater Pleiades Complex — a dispersed family of >3,000 related stars spanning ~1,900 ly, tripling the known membership context. This doesn’t change the visual M45 appearance but reframes cluster dynamics.