Head-to-Head Astrophysical & Observational Comparison

Betelgeuse vs Rigel Supergiant Comparison

Compare Orion's two flagship supergiant stars—red supergiant Betelgeuse (Alpha Orionis) and blue supergiant Rigel (Beta Orionis)—in temperature, size, and mass.

Scientific Rationale for Comparison: Anchored at opposite corners of Orion, Betelgeuse and Rigel offer the night sky's most dramatic naked-eye demonstration of Wien's displacement law and massive-star evolution across the Hertzsprung–Russell diagram.

Compared Celestial Objects

Semiregular red supergiant variable star

Betelgeuse (Alpha Orionis Red Supergiant)

Coordinates, competing optical vs radio distances (168 vs 222 pc), radius, Great Dimming physics, and observing guide for Betelgeuse.

Constellation: Orion · Coords: 05h 55m 10.31s, +07° 24′ 25.4″

Blue supergiant multiple star system (Alpha Cygni variable)

Rigel (Beta Orionis Blue Supergiant)

Coordinates, Hipparcos distance (264 pc), luminosity (120,000 L☉), Rigel BC companion, and observing guide for Rigel in Orion.

Constellation: Orion · Coords: 05h 14m 32.27s, -08° 12′ 05.9″

Normalized Shared Parameter Table

Normalized physical and observational parameters comparing Betelgeuse (Alpha Orionis Red Supergiant) and Rigel (Beta Orionis Blue Supergiant)
ParameterUnit / ScaleBetelgeuse (Alpha Orionis Red Supergiant)Rigel (Beta Orionis Blue Supergiant)
Apparent Visual Magnitude (V)mag+0.50 (variable +0.0 to +1.61)+0.13 ± 0.03
Effective Temperature (Teff)K3,600 ± 66 K (M1–M2 Ia-ab)12,100 ± 150 K (B8 Ia)
B−V Color Indexmag+1.85 ± 0.02 (deep orange-red)−0.03 ± 0.01 (blue-white)
Bolometric LuminosityL☉(1.26 ± 0.22) × 10⁵ L☉(1.20 ± 0.15) × 10⁵ L☉
Photospheric RadiusR☉764 +116/−62 R☉ (~3.5 AU)78.9 ± 7.4 R☉ (~0.37 AU)

Astrophysical & Observational Synthesis

Remarkably, Betelgeuse and Rigel radiate almost identical total bolometric luminosities (~120,000 L☉) and descend from ~18–21 M☉ OB progenitors of the Orion OB1 association. Their starkly different appearances stem from their surface temperatures: Rigel's 12,100 K photosphere radiates intensely in the blue and near-ultraviolet from a 79 R☉ sphere, whereas Betelgeuse has swollen to ~764 R☉—nearly ten times Rigel's diameter—cooling its convective photosphere to 3,600 K and shifting most of its photon output into the near-infrared.

While Hipparcos parallax places Rigel at 264 ± 24 pc, Betelgeuse's bloated, boiling convection cells shift its optical photocentre by more than its parallax angle, producing competing optical (168 pc) vs VLA radio (222 pc) distance measurements.

Practical Visual Observing Takeaway: Glance back and forth between Orion's northeast shoulder (Betelgeuse) and southwest foot (Rigel) with the unaided eye to see an 8,500 K surface-temperature difference directly in starlight color.
Reference Guide

Stellar Spectral Classification (OBAFGKM)

Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.

Reference Guide

Apparent vs Absolute Magnitude Explained

Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.

Reference Guide

Trigonometric Parallax, Parsecs & Gaia DR3

How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.

Primary Catalogs & Scientific Sources

  • Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
  • General Catalogue of Variable Stars (GCVS) & AAVSO VSX (v5.1 (2026 update)): Samus, N. N., et al. 2017, Astronomy Reports, 61, 80 (General Catalogue of Variable Stars: Version GCVS 5.1) — Sternberg Astronomical Institute / AAVSO
  • SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg