Tau Canis Majoris
Scientific overview
Tau Canis Majoris is a blue supergiant in the constellation Canis Major (Canis Majoris), lying about 2,992.3 light-years from Earth.
Class O. Extremely hot, luminous blue stars. They are massive, short-lived, and rare, pouring out ultraviolet light. Such stars have surface temperatures around ≥ 30,000 K and appear blue to the eye.
Physical properties
| Spectral type | O9Ib |
| Luminosity class | Ib |
| Apparent magnitude | 4.37 |
| Absolute magnitude | -5.44 |
| Luminosity (Sun = 1) | 13,098 |
| Colour index (B−V) | -0.132 |
| Distance | 2,992.3 ly (917.43 pc) |
Values are real catalogue data; fields without a reliable value are omitted, never estimated.
Precision measurements
Astrometry and astrophysics from SIMBAD and Gaia DR3 · Gaia DR3 5616537017987940736 · elevated RUWE
| Parallax | 0.5765 ± 0.7371 mas | SIMBAD · measured |
| Distance | 3216.4 pc | Gaia · estimated |
| Proper motion (RA) | -1.815 mas/yr | SIMBAD · measured |
| Proper motion (Dec) | -0.496 mas/yr | SIMBAD · measured |
| Radial velocity | 49.4 ± 1.4 km/s | SIMBAD · measured |
| Spectral type | O9II | SIMBAD · catalogued |
| Right ascension (ICRS) | 109.7 deg | SIMBAD · measured |
| Declination (ICRS) | -24.9544 deg | SIMBAD · measured |
Full field-level provenance
- Parallax: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · plx_value · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Distance: ESA Gaia astrometric survey · Gaia EDR3 · Bailer-Jones (2021) · external.gaiaedr3_distance · r_med_geo · row 5616537017987940736 · Bayesian estimate · retrieved 2026-07-11
- Proper motion (RA): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmra · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Proper motion (Dec): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmdec · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 1977ApJ...214..759C · direct catalogue measurement · retrieved 2026-07-11
- Spectral type: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · sp_type · 2014ApJS..211...10S · catalogue identifier/value · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
measured = direct catalogue value · estimated = Bayesian inference (Bailer-Jones distance) · modeled = model output (Gaia GSP-Phot). Fields a source did not provide are omitted, never invented.
Evolution
A blue supergiant is among the most luminous stars known — enormous, hot, and massive. Many end their lives as supernovae.
Location in the sky
Knowledge connections
- In constellationCanis Major
Related stars in Canis Major
Sources
The primary and reference sources this topic draws on.
- HYG DatabaseHYG Database (Hipparcos + Yale Bright Star + Gliese), by D. Nash / astronexus
Aggregated, openly-licensed star catalogue combining Hipparcos, the Yale Bright Star Catalogue, and the Gliese Catalogue of Nearby Stars.
- HipparcosESA Hipparcos space astrometry mission
High-precision parallax, magnitude, and position for ~118,000 stars.