Thursday, 19 June 2025

A little ramble through Carina the Keel

 The constellation of Argo Navis no longer exists as one constellation. It was at one time the largest constellation in the sky but in the 1750s the French astronomer Nicolas -Louis de Lacaille 1713-1762 divided it up into three smaller constellations, Carina the Keel Puppis the Poop and Vela the Sails.

 The original constellation was built by Glaucus for Jason and his 50 argonauts on their quest for the Golden Fleece. This fleece had come from a magical ram which was able to fly and which has rescued two royal children from a cruel stepmother, carrying them to the land of king Aetes. After the ram died the fleece was placed in a tree in a scared grove guarded by a particularly nasty dragon. Much to the annoyance of King Aetes Jason managed to kill the dragon and took the fleece back to his own country.

Among the heroes concerned in this expedition were Hercules and the heavenly twins Castor and Pollux. We will meet them in the sky later.

 An Egyptian story connected with Argo Navis said that it was the ark that carried Isis and Osiris over the great flood. In India the Hindus thought that the ship did the same thing but carried Ise and Iswara who were their versions of Isis and Osiris.

Carina is the brightest of the three parts of the old Argo Navis, its brightest star Canopus is the second brightest star in the sky, but unfortunately it cannot be seen from Britain. The name Canopus appears to mean at least according to some references as ‘But of Yesterday’

The Egyptians called the star Kaji Nub which means Golden Earth, this may refer to the brightness of the star and its nearness to the horizon. while the general Arabic name is Suhail meaning the Plain. This word was a personal title in Arabia the symbol of what is brilliant, glorious and beautiful.

To the Persian astronomers the name Suhail means wisdom and is seen in their name for the star, Al Anwar I Suhail, which means the Lights of Canopus. Another Arabic name for the star is Al Fahl or the Camel Stallion.

The Hindus called it Agastya an inspired sage a son of Varuna, the goddess of the Water. In Sanskrit literature the star is referred to in its heliacal rising with certain religious festivals. While in China it was Laou Jin or the Old Man.

Canopus as I have already mentioned is the second brightest star in the sky with a magnitude of -0.7 it is an A class giant star being hotter than the Sun and lies at a distance of 310 light years away.

If Canopus which is 310 light years away was placed at the same distance as Sirius in Canis Major is to us a mere 8.5 light years then Canopus would massively outshine the Dog Star.

Canopus is used in navigation by aircraft and space craft. It is what is referred to as a ‘star-tracker’ the Mariner 4 probe that flew by Mrs in 1965 and showed that there was no vegetation or life there used Canopus as a navigation reference point to reach Mars.

Beta or Miaplacidus which means ‘Placid Waters’ is a star of magnitude 1.7 it’s an A class giant star with a surface temperature of 8,600`C , making it hotter than our Sun and is 113 light years away.

Epsilon is one of 57 navigation stars that are used by the RAF. It is 610 light years away; epsilon is a K class giant star and is cooler than our Sun. The star has a magnitude of 1.9 slightly brighter than the North Star. Epsioln does not seem to have a name attached to it.

Iota or Aspidiske which means ‘Shield’ which I assume refers to a shield on the ship the Argo has a magnitude of 2.2 and is an A9 class supergiant star much hotter than the Sun, it is 690 Light years away. Due to the wobbling or precession of the Earth Aspidiske will become the South Pole star in 8100 CE.

Theta has a magnitude of 2.8, it’s a B class star indicating it is hotter than the Sun. Theta lies at a distance of 460 light years.  it is the brightest star in the open star cluster IC 2602, a cluster with the letters IC stands for Index Catalogue and was published in 1896 as an addition to the NGC or New General Catalogue which was produced in 1888. IC 2602 is known as the southern Pleiades, there are about 75 stars there.

Eta which does not appear to have any Greek or Arabic names might have been known to the ancient Babylonians Ea or Ia the Lord of the Waves, while the Chinese knew the star as Tseen She, or Heavens Altarsa .

However, whatever name is given to eta it is a very remarkable star, it was recorded by Edmund Halley in 1677 as a star or around magnitude 4.0. During the next 100 years it slowly brightened to about magnitude 2.0 but then it faded again to magnitude 4.0. In 1820 it rose once again to magnitude 2.0, then in April 1843 it suddenly brightened to magnitude -0.8 it outshone every star apart from Sirius. By 1866 it had dropped below naked eye visibility, it is now around magnitude 4.5. So, what’s going on?

According to theory eta should have destroyed itself with the massive eruption of 1843 but it didn’t, the theory now is that eta is in the throes of destroying itself in another massive explosion. Most astronomers think that eta has one final stage to go through, becoming what is known as a Wolf-Rayet star.

Wolf-Rayet stars represent a final burst of activity before a huge star begins to die. It could be tomorrow or within the next 100,000 years which on the cosmic scale is a blink of the eye. These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”. Their names come from two French astronomers, Charles Wolf and Georges Rayet, who discovered the first known star of this kind in 1867. When eta does explode it will be spectacular!

Eta lies within NGC 3372 or the Carina Nebula, and at a distance of around 8,500 light years which is sometimes confusingly called the Eta Carina Nebula, it’s an open cluster containing many other massive very hot O class stars.

NGC 2516 is an open cluster that is both quite large and visible to the naked eye. It is located 1,100 light-years from Earth and has approximately 80 stars, the brightest of which is a red giant star of magnitude 5.2. NGC 3114 is another open cluster approximately of the same size, though it is more distant at 3,000 light-years from Earth. It is looser and dimmer than NGC 2516, as its brightest stars are only 6th magnitude.


                                                    www.theramblingastronomer.co.uk

 

 

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