The coolest of the common spectral types, typical of stars whose surface temperature is less than about 3,500 Kelvin, and characterised by a red colour.
The supergiant Betelgeuse, marking the eastern shoulder of Orion, is usually the brightest M-type star in the sky. In late 2019, Betelgeuse ejected a vast plume of material that caused the star to temporarily dim as seen from Earth, and during this period its place as the sky's brightest red star was taken by Antares in Scorpius. Imagery provided by Aladin sky atlas
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