10 Canis Majoris
10 Canis Majoris is a single Be-type star in the southern constellation Canis Major, about 1,980 light-years away. It can be seen with the naked eye as a faint blue-white star, typically magnitude 5.1 to 5.4.
Key facts:
- Type and variability: Very hot B-type star (B2) that shows emission lines and is classified as Be. It is a variable star with brightness changing from mag 5.13 to 5.44 in a 2.63-day cycle.
- Distance and motion: About 1,980 light-years away (roughly 610 parsecs). It is moving away from us at about 34 km/s.
- Size and brightness: Mass about 19 times the Sun, radius about 10 solar radii, and luminosity around 44,000 times the Sun’s luminosity.
- Temperature and gravity: Surface temperature around 25,000 K; surface gravity (log g) about 3.8.
- Rotation: Spins very fast with a rotation period of 2.63 days and a projected rotational velocity of ~205 km/s. This makes the star oblate, with an equatorial diameter about 5% larger than the polar diameter. The rotation axis is tilted about 45° to our line of sight.
- Age: Approximately 8 million years old.
- Visual companion: There is a fainter star (magnitude ~12.6) about 37 arcseconds away.
- Other names: FT Canis Majoris, HD 48917, HIP 32292, HR 2492, among others.
This page was last edited on 2 February 2026, at 22:19 (CET).