Star Constellation Facts: Carina

Carina Constellation
Image Credit: www.davidmalin.com

Carina (“the Keel”) is a large southern hemisphere constellation that is crossed by the Milky Way, making it a rich source of deep sky objects, such as star clusters and nebulae. It is one of three constellations created from a now obsolete ancient constellation called Argo Navis, which represented the ship belonging to Jason and the Argonauts from Greek mythology, with the other two being Puppis (“the poop deck”), and Vela (“the sails”). Carina contains the night sky’s second brightest star, Canopus, a white supergiant situated 313 light years that shines with an apparent magnitude of -0.72.

Location

Carina is the 34th biggest constellation in the night sky, and can be seen by observers located between +20° and -90°, although for southern hemisphere observers, it is most prominent during Autumn to mid-winter, and best seen in March. While most northern hemisphere observers will never see Carina rise above the horizon, those in the southern hemisphere will have no difficulty spotting the constellation and its brightest star, Canopus, which lies south of the bright star Sirius in Canis Major. The two brightest stars make a beautiful sight as they appear together high in the night sky, while to the south of Carina can be found the constellation of Vela, and to its west is situated Crux, also known as “The Southern Cross”.

Heavenly Waters Family

Carina is a member of the Heavenly Waters family of constellations, together with Delphinus, Equuleus, Eridanus, Piscis Austrinus, Puppis, Vela, Pyxis and Columba.

History

Greek astronomer Ptolemy listed 48 constellations in his 2nd century treatise on the stars, of which only the large, unwieldy constellation of Argo Navis has since been made obsolete. In 1752, French astronomer Nicolas Louis de Lacaille, having studied the southern skies of South Africa, subsequently created 14 new constellations, three of which were derived from Argo Navis, including Carina (“the Keel). The breakup of Argo Navis, however, was not formally recognized until the International Astronomical Union (IAU) established the 88 modern constellations in 1930.

Meteor Showers

The two minor meteor showers associated with the constellation of Carina are the Eta Carinids, which occur from January 14th to 27th, and peaks on January 21st with around two to three meteors per hour; and the even less prolific Alpha Carinids, which runs from January 24th to February 9th.

Principal Stars

– Canopus (Alpha Carinae), the night sky’s second brightest star, is a supergiant situated 313 light years distant whose spectral type astronomers have described as being either F0 (yellow-white) or more recently as A9 II (white). It shines with an apparent visual magnitude of -0.72, which would increase to -5.53 if imagined 10 parsecs (32.6 light years) from Earth, which is its measure of absolute magnitude. Canopus is around 65 times bigger than the Sun, 8 times more massive, and 15,000 times brighter.

Stars in Carina ConstellationCanopus is named after the pilot who headed the naval fleet of Menelaus of Sparta on the quest to retrieve the king’s wife, Helen, who had been abducted by Paris and taken to the city of Troy. The legend was written about in Greek writer Homer’s epic poem called The Iliad, which states that on the return journey, having successfully completed the mission, Canopus died after being bitten by a poisonous snake in Egypt. He was then honored by Menelaus, who named the port after him, as well as the bright star that was said to have risen during the king’s dedicatory speech.

– Miaplacidus (Beta Carinae), the night sky’s 29th brightest star, is a blue subdwarf found 111 light-years from our solar system with an apparent magnitude of 1.7. This roughly 260 million year old star is 7 times bigger than the Sun, with 3.5 times its mass, and 288 times its luminosity. It also has a rapid rotational velocity of 146 kms/sec. The name Miaplacidus is a mixture of the Arabic word for water (miyah), and the Latin word for placid (placidus).

– Avior (Epsilon Carinae), the constellation’s third brightest star, is also the 84th brightest star in the night sky. It is a binary system located around 660 light years away of magnitude 1.86, consisting of an orange giant (K0 III) and a blue dwarf (B2 V) fainter companion separated by 4 astronomical units (AU). The pair are believed to eclipse each other once every 785 days, with each eclipse causing a 0.12 change in magnitude.

Eta Carinae– Eta Carinae is one of the most spectacular stars in the Universe, and over the years its has ranged in brilliance from -1 magnitude to 8th magnitude, although it is currently around magnitude 6. Located 7,500 light-years distant, this stellar system is a staggering four million times more luminous than the Sun, with its biggest component, a blue variable hypergiant, around 100 times more massive. Eta Carinae undergoes intermittent powerful outbursts, and while belching out around ten solar masses it created the ten billion mile wide Homunkulus Nebula, and in April 1843 the star was recorded as being the night sky’s second brightest to Sirius, with a minus magnitude. Eta Carinae is expected to go supernova or hypernova at some stage, and being just 7,500 light-years away, while the Earth’s magnetosphere and atmosphere will protect our planet from gamma rays and some cosmic rays, the Earth’s ozone layer, satellites, and spacecraft could be adversely affected.

The southern celestial hemisphere contains three asterisms, namely the Southern Cross in Crux; the False Cross in Carina and Vela; and the Diamond Cross in Carina. The latter is composed of the constellation’s Beta, Theta, Upsilon and Omega stars, all of which are bluish in color.

Other stars of interest in Carina includes the blue variable star AG Carinae, which has an apparent magnitude of +6.96, but an intrinsic bright absolute magnitude of -10.3; the blue-white dwarf stars PP Carinae and Chi Carinae; the blue-white subgiant V357 Carinae; the white supergiants Aspidiske (Iota Carinae) and V533 Carinae; the yellow supergiant HD 84810; the yellow hypergiant V382; and the orange giant star V337 Carinae.

Notable Deep-Sky Objects

The north-eastern region of Carina lies within the Milky Way, making it a treasure trove of deep-sky objects for stargazers.

Carina Nebula– Carina Nebula (NGC 3372) is a huge 300 light-years wide diffuse nebula found 8,000 light-years distant of magnitude +1. It is four times bigger than the Orion Nebula, which is much dimmer at magnitude +4, and would therefore be better well-known if not for being located in the southern hemisphere. It is also called the Eta Carinae Nebula, as it surrounds the two massive stars Eta Carinae and HD 93129A. Contained within the Carina Nebula are a number of open star clusters, such as Trumpler 14 and Trumpler 16, as well as a further two smaller nebulae, namely the Homunculus Nebula and the Keyhole Nebula; and a spectacular stellar nursery of dust pillars called the Mystic Mountain. There can also be found several star systems, including the binary stars WR 22, WR 25, HD 93205, and HD 93250; and the triple star system HD 93129.

– Theta Carinae Cluster (Southern Pleiades) is an open cluster situated 479 light years from Earth that has a visual magnitude of 1.9. It contains around 60 stars, of which the brightest is the blue-white dwarf Theta Carinae, after which the cluster was named.

– Wishing Well Cluster (NGC 3532) is an open cluster found 1,321 light years away that has around 150 stars of magnitude 7 and fainter, including 7 red giants and 7 white dwarfs. It got its rather poetical name because the stars seen twinkling inside the cluster are said to look like silver coins shining at the bottom of a Wishing Well.

Other star clusters in Carina includes NGC 3603, The Diamond Cluster (NGC 2516), NGC 3293; and NGC 2808, a 12.5 billion years old globular cluster containing over a million stars, making it one of the Milky Way’s biggest clusters.

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