Carina (constellation)

Carina (/kəˈraɪnə, kəˈriːnə/ kə-RY-nə, -⁠REE-) is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was the southern foundation of the larger constellation of Argo Navis (the ship Argo) until it was divided into three pieces, the other two being Puppis (the poop deck), and Vela (the sails of the ship).

Carina was once a part of Argo Navis, the great ship of the mythical Jason and the Argonauts who searched for the Golden Fleece. The constellation of Argo was introduced in ancient Greece. However, due to the massive size of Argo Navis and the sheer number of stars that required separate designation, Nicolas-Louis de Lacaille divided Argo into three sections in 1763, including Carina (the hull or keel). In the 19th century, these three became established as separate constellations, and were formally included in the list of 88 modern IAU constellations in 1930. Lacaille kept a single set of Greek letters for the whole of Argo, and separate sets of Latin letter designations for each of the three sections. Therefore, Carina has the α, β and ε, Vela has γ and δ, Puppis has ζ, and so on.

Carina contains Canopus, a white-hued bright giant that is the second-brightest star in the night sky at magnitude −0.72. Alpha Carinae, as Canopus is formally designated, is 313 light-years from Earth. Its traditional name comes from the mythological Canopus, who was a navigator for Menelaus, king of Sparta.

There are several other stars above magnitude 3 in Carina. Beta Carinae, traditionally called Miaplacidus, is a blue-white-hued star of magnitude 1.7, 111 light-years from Earth. Epsilon Carinae (Avior) is an orange-hued giant star similarly bright to Miaplacidus at magnitude 1.9; it is 630 light-years from Earth. Another fairly bright star is the blue-white-hued Theta Carinae; it is a magnitude 2.7 star 440 light-years from Earth. Theta Carinae is also the most prominent member of the cluster IC 2602. Iota Carinae is a white-hued supergiant star of magnitude 2.2, 690 light-years from Earth.

Eta Carinae is the most prominent variable star in Carina, with a mass of approximately 100 solar masses and 4 million times as bright as the Sun. It was first discovered to be unusual in 1677, when its magnitude suddenly rose to 4, attracting the attention of Edmond Halley. Eta Carinae is inside NGC 3372, commonly called the Carina Nebula. It had a long outburst in 1827, when it brightened to magnitude 1, only fading to magnitude 1.5 in 1828. Its most prominent outburst made Eta Carinae the equal of Sirius; it brightened to magnitude −1.5 in 1843. In the decades following 1843 it appeared relatively placid, having a magnitude between 6.5 and 7.9. However, in 1998, it brightened again, though only to magnitude 5.0, a far less drastic outburst. Eta Carinae is a binary star, with a companion that has a period of 5.5 years; the two stars are surrounded by the Homunculus Nebula, which is composed of gas that was ejected in 1843.

There are several less prominent variable stars in Carina. l Carinae is a Cepheid variable noted for its brightness; it is the brightest Cepheid that is variable to the unaided eye. It is a yellow-hued supergiant star with a minimum magnitude of 4.2 and a maximum magnitude of 3.3; it has a period of 35.5 days.

V382 Carinae is a yellow hypergiant, one of the rarest types of stars. It is a slow irregular variable, with a minimum magnitude of 4.05 and a maximum magnitude of 3.77. As a hypergiant, V382 Carinae is a luminous star, with 212,000 times more luminosity than the Sun and over 480 times the Sun's size.

Two bright Mira variable stars are in Carina: R Carinae and S Carinae; both stars are red giants. R Carinae has a minimum magnitude of 10.0 and a maximum magnitude of 4.0. Its period is 309 days and it is 416 light-years from Earth. S Carinae is similar, with a minimum magnitude of 10.0 and a maximum magnitude of 5.0. However, S Carinae has a shorter period—150 days, though it is much more distant at 1,300 light-years from Earth.