Messier 99 (M99)

The Pinwheel Cluster's neighbour, a grand spiral notable for hosting three supernovae since 1967.

Core Principles & Analysis

• One of its arms is remarkably prominent, pulled by an unseen companion's gravity.
• Three supernovae — 1967, 1972, 1986 — have been recorded in its disc.
• Méchain discovered it in 1781; Hubble later used it to help establish galaxy distances.

Specifications & Metrics

• GALAXY TYPE: Barred spiral (SAc)
• DISTANCE: ~55 million light-years