Constellations: Carina 'the Keel' Content from the guide to life, the universe and everything

Constellations: Carina 'the Keel'

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The shield of the Science, Mathematics and Engineering faculty of the h2g2 University.Constellations: Overview | Andromeda | Antlia | Apus | Aquarius | Aquila | Ara | Aries | Auriga | Boötes | Caelum
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A boat named 'Carina'.
Under the keel nine fathoms deep,
From the land of mist and snow,
The spirit slid: and it was he
That made the ship to go.

– Samuel Taylor Coleridge: The Rime of the Ancient Mariner (1798)

Name:Carina (Latin: 'keel')
Genitive:Carinae
Meaning:'the Keel' or 'the Hull'
Short form:Car
Area:494 sq deg
Co-ordinates1:Right Ascension 09h, Declination −60°
Origin:Modern

Navigating by the Stars

In the days before computers and Global Positioning Systems to aid one's movement around the planet, sea-faring voyagers relied upon the stars for navigation. Therefore astronomy was an important science, otherwise ancient mariners would perish before they even reached their destination (if ever they did). Stars by themselves are meaningless to travellers, and almost impossible to describe in order to tell them apart. So constellations were invented, a group of stars in a certain alignment, as seen from Earth. The stars are at different distances; some are small but close, so they shine brighter than other, more massive stars, which are much further away. In ancient times 48 constellations were used to assist sailors on voyages. One of the most recognised Southern Hemisphere stars to these seafarers was Canopus, which shone like a beacon from the 'masthead' of the enormous group of stars the ancients imagined as a ship, the Argo.

Breaking up the Argo Navis

Argo Navis was one of the original 48 constellations of Ptolemy's time. It represented the fabled ship transporting Jason and the Argonauts in their search for the Golden Fleece. In the 18th Century the massive group of stars which was Argo Navis was split into three separate 'modern' constellations by French astronomer Nicolas Louis de Lacaille2 (1713 - 62). Carina, Vela 'the Sail' and Puppis 'the Stern' collectively commemorate the dismemberment of the constellation which represented the Argonauts' vessel.

Carina the Constellation

Carina (Latin meaning keel) is variously listed as being 'the hull' or 'the keel' in star catalogues and on charts. The constellation actually represents the whole hull of the boat excluding the stern.

Carina spans an area of the sky measuring just under 500 square degrees. It is bordered by Vela, Puppis, Pictor, Volans, Chamæleon, Musca and Centaurus. This Southern Hemisphere constellation boasts the second brightest star viewable from Earth (excluding the Sun) and a hypergiant star which in its death-throes has created an astonishing nebula comparable to Messier42 in Orion.

Stars of Carina

The scientific star names are simple to understand, they use lower case Greek letters combined with the genitive of the constellation name, known as the 'Bayer designation'. Some stars have proper names as well, for example, alpha Carinae is Canopus. Other, unnamed stars are known by their catalogue number. The stars of Argo Navis kept their original Bayer designations when the constellation was broken up, so some Greek letter stars are missing from Carina.

Beta Carinae, Miaplacidus, is a binary star system comprising a white subgiant and a yellow-white dwarf.

Chi Carinae bears the common name Drus meaning 'oak tree'. It represents the wood from which the ancient ship of legend was constructed.

Omega Carinae has the rather striking name Simiram which translates to 'the sunlit sea'.

HD 97950 is a multiple system containing the red hypergiant HD 97950 A-1 on the verge of blowing itself to smithereens.

Theta Carinae

Theta Carinae is a young, silicon-rich blue-white dwarf with a temperature anomaly – it's not hot enough for its class, so it carries the label 'peculiar star'. Theta Carinae is nestled among open star cluster IC 2602, popularly known to northern astronomers as the Southern Pleiades, but southern sky-watchers know it as the Theta Carinae Cluster.

Canopus (Alpha Carinae)

Alpha Carinae is the white supergiant Canopus, one of only four stars viewable from Earth (not including the Sun) registering a minus magnitude. Canopus (also 'Kanopus') in legend was King Menelaus' helmsman when the Spartans were on their way to the Trojan War. When the king became threatened by a snake, Canopus sacrificed himself to save his liege. An Egyptian seaport honours the hero Canopus by carrying the same name, and possibly the word 'canopic' stems from it when referring to the ancient Egyptian funerary equipment known as Canopic Jars.

Eta Carinae

First catalogued by Edmond Halley in 1677, the truly astonishing eta Carinae is a hypergiant peculiar star at the pre-supernova stage. It is well over a hundred times the mass of our Sun3, and four million times brighter. Eta Carinae is possibly the most luminous star known, and it emits the extremely rare astrophysical phenomena called ultraviolet laser4. It underwent an outburst, belching out the equivalent of ten solar masses, creating the bi-polar Homunculus Nebula which measures ten billion miles across. The expelled material is travelling at a velocity of about 1½ million mph. Light from the expulsion reached Earth in April 1843, registering a minus magnitude. For a short while it was the second brightest star in the night sky (after Sirius, alpha Canis Majoris). The Homunculus Nebula is one of the most spectacular sights viewable from Earth.

The star is on the verge of self-destruction; when it blows it is expected to go hypernova. If it does, the gamma ray burst within our own galaxy might cause shockwaves which affect the Earth. It's not known how far in the future this will occur; suffice to say this is one mega ticking-time bomb. It may have already occurred, but the light hasn't reached us yet. What we are looking at is effectively a snapshot of something which happened (in real time) seven and a half thousand years ago. We may not witness the hypernova, because it might not happen for another several hundred thousand years5, then again, it could happen tomorrow. In the meantime it is the cause of intense debate among astronomers and astrophysicists.

Star Table

StarDesignationName or
catalogue number
Brightness (m)Distance
(light years6)
Spectral classification
and/or comments
α Caralpha CarinaeCanopus−0.72 var310White supergiant
β1 Carbeta1 CarinaeMiaplacidus+1.67 var109White subgiant
β2 Carbeta2 CarinaeHD 77370+5.17 var84Yellow-white dwarf
ε1 Carepsilon1 CarinaeAvoir+1.9 var600Orange giant
ι Cariota CarinaeAspidiske+2.2 var620White supergiant
η Careta CarinaeHD 93308+5 var7,500Hypergiant
θ Cartheta CarinaeHD 93030+2.7 var440Blue-white dwarf
υ1 Carupsilon1 CarinaeHD 85123+3 var1,600White supergiant
υ2 Carupsilon2 CarinaeHD 85124+6.2 var1,600Blue-white giant
χ Carchi CarinaeDrus+3.4 var360Blue-white subgiant
ω Caromega CarinaeSimiram+3.3 var350Blue-white giant
HD 97950 Part of NGC 3603+9 var20,000Multiple system

Asterism: Diamond Cross

The southern sky has three 'cross' asterisms in close proximity and it's easy to get them confused. The 'Southern Cross' is the constellation Crux. The 'False Cross' is made up of four stars, two each from different constellations: delta and kappa Velorum, and iota and epsilon Carinae. It is the third cross we are concerned with here: the Diamond Cross. This distinctive shape is formed by the four bright stars: Miaplacidus (beta Carinae), theta Carinae, upsilon Carinae, and Simiram (omega Carinae).

New General Catalogue and Index Catalogue (NGC/IC)

The NGC was compiled by John Louis Emil Dreyer (the director of the Armagh Observatory from 1882 to 1916). This was later expanded to include newer discoveries, and is being continually updated as the NGC/IC Project.

IC 2602 is a stunning open star cluster which was discovered by Lacaille. Due to the close proximity of the star marked theta Carinae, it is known as the Theta Carinae Cluster in the Southern Hemisphere, but northern astronomers refer to it as The Southern Pleiades.

The Great Carina Nebula (NGC 3372) was discovered by Lacaille in 1751. It is a giant diffuse (emission) nebula with star-forming regions. The hypergiant peculiar star eta Carinae was born here. Another catalogued feature of NGC 3372 is the darker Keyhole Nebula, NGC 3324.

The Caldwell Catalogue was compiled by Sir Patrick Moore with the intention to create a list to challenge the 'backyard astronomer' – keen amateurs like himself. NGC 2516 is an open star cluster which also carries the label Caldwell 96.

NGC 3293 is a striking open cluster which has between 60 and 70 stars of different colours and magnitude, including an orange, a blue and a white star lined up through the centre. It has been compared in beauty to the more well-known Jewel Box Cluster of nearby constellation Crux, and bears the enigmatic common name 'Gem Cluster'.

NGC 3114 is a gorgeous collection of blue and blue-white stars with a few orange giants scattered about. Surprisingly this treasure of the southern skies has no common name, so perhaps Dun 297 deserves a good press agent!

NGC 3324 was first catalogued as an open star cluster with nebulosity. However, since the NGC/IC project got underway some revisions have been made, and NGC 3324 is now classified 'diffuse nebula or supernova remnant'. The original NGC data appears in the table below.

NGC 3532 has the glorious, image-provoking common name The Wishing Well Cluster, referring to the stars' likeness to glittering coins reflecting the shining sun through the water at the bottom of a well.

NGC 3603 is a good example of the complete life cycle of stars. This open cluster with nebulosity lies 20,000 light years away, and it contains star-forming regions, a star with a protoplanetary disk, main sequence stars, blue supergiant Sher 25, and also a multiple system containing the red hypergiant HD 97950 A-1 which is building up to the supernova stage.

IC 2220 boasts the more popular name of the Toby Jug Nebula due to its imagined similarity to the drinking mug. This type of nebula shines by reflected light from a nearby star, a sort of interstellar belch. The Toby Jug Nebula is unusual in that its colour is sulphuric yellow. Because it surrounds irregular variable red giant V341 Carinae, perhaps the star is emitting its gas from the wrong end!

NGC 3119 is a bright emission and/or reflection nebula fuelled by a Wolf-Rayet star (these types of star are named after their discoverers Charles Wolf and Georges Rayet). They are blue supergiants, over 20 times the mass of our Sun, which eject stellar wind at a phenomenal speed. They have a high rate of mass loss, equivalent to an Earth mass per year. This shortens the life of the stars and will eventually cause them to go supernova. However, the NGC/IC project has reclassified NGC 3199 as a 'diffuse nebula or supernova remnant', so the star could have already self-destructed.

Three of the planetary nebulae listed below, IC 2501, IC 2448 and IC 2553 were discovered by Scottish astronomer Williamina Paton Stevens Fleming  (1857 - 1911). Though her job was maid to Professor EC Pickering of Harvard College Observatory, she made a better assistant than some of his students, so he ended up giving her a job classifying stars and examining photographic plates. A major find in 1888 was the enigmatic Horsehead Nebula  (Fleming 21/Barnard 33/IC 434) in Orion, but years passed before she finally got credit for its discovery. In 1899 the title of Curator of Astronomical Photographs was awarded to Williamina Fleming, the first time such a position had been given to a female. She was made an honorary member of the Royal Astronomical Society of London in 1906.

NGC and IC Table

CatalogueNameTypeBrightness (m)Distance
(light years)
Remarks
NGC 3372Great Carina NebulaEmission nebula+6.27,500NGC 3372+NGC 3324
NGC 3324Keyhole NebulaDark nebula+6.77,500Part of Great Carina Nebula
NGC 2516Caldwell 96Open cluster+3.81,300Discovered in 1752 by
Nicolas Louis de Lacaille
NGC 3114Dun 297Open cluster+4.22,940Discovered by
James Dunlop (1826)
NGC 3247h 3250Open cluster+7.64,570Discovered by
John Herschel (1834)
NGC 3293Gem clusterOpen cluster+4.78,480Discovered in 1751 by
Nicolas Louis de Lacaille
NGC 3324Dun 322Open cluster
with nebulosity
+6.710,800Discovered by
James Dunlop (1826)
NGC 3532Wishing Well ClusterOpen cluster+3.01,300Discovered in 1751 by
Nicolas Louis de Lacaille
NGC 3603h 3334Open cluster
with nebulosity
+9.120,000Discovered by
John Herschel (1834)
NGC 3059h 3205Galaxy+11.148.25 millionBarred spiral
NGC 2808Dun 265Globular cluster+6.331,200Discovered by
James Dunlop (1826)
NGC 3211h 3242Planetary nebula+11.85,900Discovered by
John Herschel (1834)
IC 2501Fleming 101Planetary nebula+11.35,642Discovered in 1904
by Williamina Fleming
IC 2448Fleming 80Planetary nebula+11.510,100Discovered in 1898
by Williamina Fleming
IC 2553PK 285-5Planetary nebula+1313,400Discovered in 1893
by Williamina Fleming
IC 2602Southern Pleiades/
Theta Carinae Cluster
Open cluster+1.947940+ stars
IC 2714Dun 281Open cluster+8.23,900Discovered by
James Dunlop (1826)

Henize 3-401

The planetary nebula Henize 3-401 doesn't feature in the NGC but is worthy of a mention due to its unusual elongated shape. Considering the star is spinning it is a puzzle why the nebula is such a shape, as if it is being squeezed and the gaseous matter is being ejected from both ends. Even astrophysicists don't know for sure but some educated guesses for the cause are a possible unseen binary companion, or it may be that the star's magnetic field is involved.

Meteor Showers

The space debris which creates a meteor shower comes from the tail of a comet, as the Earth crosses where the comet passed previously on its own orbit. There are two meteor showers connected with this constellation, although neither are prominent. The Eta Carinids last from 14 to 27 January. The second shower is called the Alpha Carinids, which occur between 24 January and 9 February.

Extrasolar Planets in Carina

There have been several extrasolar planetary systems found in the constellation Carina. Figures given in the table below are the length of the planet's orbital period around its parent star, which we know of as a year. The mass of the extrasolar planet is compared to that of Jupiter, our Solar System's largest planet, known by astronomers as the 'Jovian scale'.

The star OGLE-TR-111 has one confirmed planet OGLE-TR-111 b and another is suspected but at the time of writing the data is unconfirmed. Only published planet information appears in the table below.

The star HD 63765 is an insignificant yellow dwarf like our Sun, but it does boast a planet in the system's habitable zone. Unfortunately, HD 63765 b is a gas giant with approximately 2/3rds the mass of Jupiter.

Extrasolar Planets Table

Star name or
catalogue number
Planet
catalogue number
Planet size
(Jovian scale)
Orbital period
(Earth days)
Year of discoveryComments
HD 65216HD 65216 b1.26132003Gas giant; eccentric orbit
OGLE-TR-111OGLE-TR-111 b0.542004Hot subjovian
OGLE-TR-113OGLE-TR-113 b1.41.32004Hot Jupiter
OGLE-TR-132OGLE-TR-132 b1.71.142004Hot Jupiter
OGLE-TR-182OGLE-TR-182 b41.012007Hot Jupiter
OGLE-TR-211OGLE-TR-211 b3.61.032007Hot Jupiter
OGLE2-TR-L9OGLE2-TR-L9 b52.52008Hot Jupiter
HD 63765HD 63765 b0.693562009Gas giant/
habitable zone

Carina Down on Earth

  • There is a suburb of Brisbane in Australia called Carina.

  • Carina is a medical term meaning any sort of a keel-like structure, for example the breastbone of a bird.

  • The 'Carina' is a model of car made by Toyota that was in production from 1970 to 2000.

  • Careening is the process of cleaning the hull of a boat.

  • Carina is a popular Christian name for a girl; a 19th Century invention, derived from the diminutive of 'cara' meaning beloved. eg: Carina Wint is an English photographer based in Panama City, Panama; singer/songwriter Carina Round was born in Wolverhampton, UK, and Carina Karlsson is a poet and freelance writer from Finland.

1Current IAU guidelines use a plus sign (+) for northern constellations and a minus sign (−) for southern ones.2Lacaille's posthumous catalogue Coelum Australe Stelliferum described 14 new constellations and 42 nebulous objects among almost 10,000 southern stars from information garnered on a 1751 – 54 expedition to the Cape of Good Hope.3Robert Zimmermann states that eta Carinae is 120 solar masses in his article in Astronomy, issue February 2000; Professor Jeff Hester of the Arizona State University is on record as estimating the mass as 150x.4The waves from laser light are very precisely aligned, and they only occur at a few specific frequencies.5Such massive stars only have a lifespan of about a million years, a relatively short lifetime for a star.6A light year is the distance light travels in one year, roughly 5.88 trillion miles or 9.46 trillion km.

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