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 63752 HIP 61362 HIP 63937 HIP 63942 HIP 63998 HIP 61495 HIP 61543 HIP 61563 HIP 61652 HIP 61658 HIP 61667 HIP 61686 HIP 61706 HIP 64245 HIP 64267 HIP 64334 HIP 64339 HIP 64391 HIP 61903 HIP 6191 HIP 61975 HIP 6453 HIP 64530 HIP 62030 HIP 64561 HIP 62064 HIP 6207 HIP 64640 HIP 64645 HIP 62168 HIP 62247 HIP 64768 HIP 62355 HIP 64880 HIP 64935 HIP 65006 HIP 65011 HIP 65012 HIP 65016 HIP 62556 HIP 62588 HIP 65080 HIP 65120 HIP 65122 HIP 62687 HIP 62767 HIP 62772 HIP 65248

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