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Last updated August 29, 2025

Red Dwarfs: The Smallest Stars

Red dwarf

Red Dwarfs

Red dwarfs are M-type stars, much less massive and luminous than the Sun. Their mass typically ranges from 0.08 to 0.6 M☉, and their surface temperature is between 2,400 and 3,800 K. Their energy is produced by the fusion of hydrogen very slowly, giving them an extremely long lifespan.

Main characteristics:

Internal structure of a red dwarf:

Stellar Evolution

Red dwarfs evolve very slowly:

  1. Main sequence: stable hydrogen fusion over very long periods
  2. Final phase: they generally do not become significant red giants and end as small white dwarfs after billions of years

The Most Studied Red Dwarfs

Characteristics of Studied Red Dwarfs
StarSpectral TypeMass (M☉)Radius (R☉)Temperature (K)Remarks
Proxima CentauriM5.5V0.120.143,050Closest star to the Sun
Barnard's StarM4V0.160.203,100Well-studied low-mass star
TRAPPIST-1M8V0.0890.122,550Famous compact planetary system with exoplanets
Luyten's StarM3.5V0.260.353,450Nearby star with detected planets
Wolf 359M6V0.090.122,800Very faint and close to the Sun
Gliese 581M3V0.310.293,200Famous for its potentially habitable exoplanets
YZ CetiM4.5V0.130.163,100Nearby star with a compact planetary system
GJ 667 CM1.5V0.310.423,700Part of a triple system, several detected planets
Ross 128M4V0.170.203,180Nearby and relatively calm, exoplanet in the habitable zone
CHXR 73M3.25V0.320.353,490Young star in the Chamaeleon constellation, age ~2 million years

Sources: NASA – Stellar Data, International Astronomical Union.

Understanding the M5V Notation (Red Dwarfs)
Notation ElementExampleMeaningPhysical Details
Main letterMSpectral typeVery cool red stars, temperature 2,400–3,800 K
Number5Spectral subtype0 = hotter, 9 = cooler. M5 is intermediate
Roman letterVLuminosity classV = main sequence dwarf, stable hydrogen fusion

Source: International Astronomical Union – Stellar Classification

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