Procyon vs Sirius
The two dog stars stand only about an hour of right ascension apart and are both among the Sun's nearest bright neighbours — Procyon at 11.46 light-years, Sirius at 8.60. Sirius takes the sky comfortably at magnitude −1.44 against 0.40, a 1.84-magnitude margin worth roughly 5.5 times the light. Intrinsic output runs the same way but far less steeply: absolute magnitudes of +1.45 and +2.67 place Sirius about three times ahead. The F-type Procyon is thus the cooler and the more distant of a genuinely well-matched pair, and the two are among the very few first-magnitude stars close enough for their parallaxes to have been measured in the nineteenth century.
Property comparison
| Property | Procyon | Sirius |
|---|---|---|
| Designation | 10Alp CMi | 9Alp CMa |
| Constellation | N/A | Canis Major |
| Spectral Class | Class F — F-type (Yellow-White) | Class A — A-type (White) |
| Apparent Magnitude | +0.40 | -1.44 |
| Absolute Magnitude | 2.67 | 1.45 |
| Distance | 11.5 ly | 8.6 ly |
| Mass | N/A | N/A |
| Radius | N/A | N/A |
| Temperature | N/A | N/A |
| Luminosity | N/A | N/A |
Full data for each star: Procyon · Sirius
Key differences
Key Differences
- ◆ Procyon (Alpha Canis Minoris) and Sirius (Alpha Canis Majoris) are both among the Sun's nearest stellar neighbours.
- ◆ Sirius is the brightest star at magnitude −1.46; Procyon is the eighth-brightest at magnitude 0.34.
- ◆ Sirius is an A-type star (hotter, more massive); Procyon is an F-type star closer to the Sun in character.
- ◆ Both are binary systems with white dwarf companions (Sirius B and Procyon B).
- ◆ Procyon is 11.46 light-years away; Sirius is slightly closer at 8.6 light-years.
When to Observe
Procyon
Procyon culminates at midnight in mid-January and remains a fixture of evening skies from January into April. Its declination of +5° places it near the celestial equator, so it rises for essentially every inhabited latitude.
Sirius
Sirius culminates at midnight around 1 January, a fortnight before Procyon, and shares the same season. At declination −16° it stands lower in the south for northern observers.