Class M — M-type (Red)

M-type stars, commonly called red dwarfs, are the coolest and most common main-sequence stars, with surface temperatures of 2,400 to 3,700 K. They make up about 76% of all main-sequence stars, yet none are visible to the naked eye from Earth due to their low luminosity. Proxima Centauri (M5.5Ve), the closest star to the Sun, is an M-type star. Red dwarfs have extremely long lifetimes — trillions of years — far exceeding the current age of the universe. Many host exoplanets, including Proxima Centauri b and the TRAPPIST-1 system.

M-type stars are the coolest, smallest, and by far the most abundant stars in the universe. With surface temperatures below 3,700 K and masses from 0.08 to 0.45 solar masses, red dwarfs constitute approximately 76% of all main-sequence stars — yet not a single one is visible to the naked eye from Earth, despite Proxima Centauri (M5.5Ve) being the nearest star beyond the Sun at just 4.24 light-years. Their extreme longevity (trillions of years) means no M dwarf has ever died of old age in the history of the universe.

Characteristics

M-type spectra are dominated by titanium oxide (TiO) molecular absorption bands, which create their characteristic deep red color. M dwarfs are fully convective below about 0.35 solar masses — meaning they mix their entire hydrogen supply, greatly extending their lifetimes. However, this convection drives powerful magnetic fields that produce frequent, intense flares — some M dwarfs can brighten by factors of 100 in minutes. Their habitable zones lie very close to the star, meaning potentially habitable planets are likely tidally locked. The M class also includes red giants and supergiants — evolved massive stars like Betelgeuse (M1-M2Ia-Iab).

Notable Examples

Proxima Centauri (M5.5Ve) hosts Proxima b, an Earth-mass planet in the habitable zone of our nearest stellar neighbor. TRAPPIST-1 (M8V) has seven Earth-sized planets, three in the habitable zone — the most Earth-like system known. Barnard's Star (M4Ve) is the fastest-moving star in Earth's sky and a target of exoplanet searches since the 1960s. Betelgeuse (Alpha Orionis, M1-M2Ia-Iab) is an M-type red supergiant whose Great Dimming event in 2019-2020 captivated global attention — it will eventually explode as a supernova visible in daylight.

HIP 75054 HIP 7506 HIP 75143 HIP 75144 HIP 75170 HIP 75175 HIP 75187 HIP 7520 HIP 75202 HIP 75207 HIP 75286 HIP 75337 HIP 75393 HIP 75456 HIP 75485 HIP 75497 HIP 7554 HIP 75556 HIP 75584 HIP 75620 HIP 75674 HIP 75686 HIP 75697 HIP 75710 HIP 75727 HIP 75813 HIP 75815 HIP 75847 HIP 75878 HIP 7592 HIP 75943 HIP 7598 HIP 75992 HIP 76 HIP 76022 HIP 76036 HIP 76044 HIP 76047 HIP 76074 HIP 76075 HIP 76107 HIP 76111 HIP 76152 HIP 7620 HIP 76202 HIP 76207 HIP 76215 HIP 76279

Frequently Asked Questions

What is a class M star?

Class M (M-type (Red)) stars are red stars. M-type stars, commonly called red dwarfs, are the coolest and most common main-sequence stars, with surface temperatures of 2,400 to 3,700 K. They make up about 76% of all main-sequence stars, yet non

How hot are class M stars?

Class M stars have surface temperatures between 2,400 K and 3,700 K.

What color are class M stars?

Class M stars appear red.

How many class M stars are in the StarFYI database?

StarFYI currently catalogs 5,834 class M stars.

How luminous are class M stars?

Very dim, less than 0.08 solar luminosities

Class M — M-type (Red)

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Characteristics

Notable Examples

Frequently Asked Questions