V399 Carinae

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V399 Carinae: a bright, variable supergiant in Carina

V399 Carinae is a very bright star in the constellation Carina and can be seen with the naked eye, usually shining around magnitude 4.63 to 4.72. It’s a luminous supergiant, with a spectral type that has been listed as A5Iae to F0Ia, and its spectrum shows signs of strong mass loss.

Location and cluster
- It lies near the open star cluster IC 2581 and is the brightest member of the cluster.
- If it is part of IC 2581, it is about 7,500 light-years from Earth (though the exact distance is uncertain).

Size, mass, and brightness
- Size: about 206 times the Sun’s radius.
- Mass: roughly 23 solar masses.
- Luminosity: around 73,000 times the Sun’s brightness.
- Temperature: about 8,000 K.
- Surface gravity is very low, reflecting its extended atmosphere.

Variability
- Its brightness changes slightly, from magnitude 4.63 to 4.72.
- Over the years, studies have suggested different variability periods (roughly 47 to 88 days). It is often classified as a semiregular variable or an alpha Cygni-type variable.

Other names
- It is also known as P Carinae, 195 G. Carinae, HR 4110, HD 90772, and other catalog identifiers.