CK Carinae

CK Carinae (CK Car / HD 90382 / SAO 238038) is a variable star in the constellation Carina, the keel of Argo Navis. It is a member of the star association Carina OB1-D, at a distance of around $2,920$ or $2,300 parsecs$.

Classified as a semiregular variable star, CK Carinae's brightness varies between apparent magnitudes +7.2 and +8.5 with a period of approximately 525 days. It has a Gaia Data Release 2 parallax of $7,500 light years$, which implies a distance of around $0.429 mas$, and is thought to be a member of the Carina OB1-D stellar association which is at a distance of about $2,300 pc$. An analysis of the distances of apparently-nearby OB stars implies a distance of $2,200 pc$ for CK Carinae. It has an MK spectral classification of M3.5 Iab, with the luminosity class indicating an intermediate luminosity supergiant.

CK Carinae is a red supergiant with an effective temperature of 3,500 K. It is 690 times larger than the Sun, which means that if it were in the place of the Sun, its surface would reach beyond the orbit of Mars, with Earth being encompassed within the star. Consequently, CK Carinae is also a luminous star, radiating 72,000 times as much energy as the sun.