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 8114 HIP 60867 HIP 60874 HIP 81165 HIP 81201 HIP 81207 HIP 5934 HIP 59889 HIP 59921 HIP 59947 HIP 81309 HIP 62996 HIP 6325 HIP 63506 HIP 61003 HIP 61009 HIP 61014 HIP 61015 HIP 61022 HIP 61024 HIP 63602 HIP 63642 HIP 6365 HIP 61163 HIP 61226 HIP 61286 HIP 63845 HIP 63850 HIP 61404 HIP 61413 HIP 61495 HIP 61532 HIP 61543 HIP 61563 HIP 61652 HIP 61658 HIP 61667 HIP 61686 HIP 64245 HIP 64267 HIP 61749 HIP 6430 HIP 61806 HIP 64370 HIP 61839 HIP 64391 HIP 61903 HIP 6191

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