The ‘great star of the south’ was once the most luminous in our sky. Slowly and surely, in about 480,000 years, it will be again.
HERE’S an undeniable truth: you will find the brightest stars south of the celestial equator. we hear and read more about northern stars because most citizens of planet Earth live in the northern hemisphere.
We really do hold all the jewels though and here’s the story of the ”great star of the south”, Canopus.
The name comes from the Greek . Throughout the centuries it has morphed into its current handle as Canopus. It’s named in honour of the chief pilot of King Menelaus, guiding the Greek fleet to Troy for the well-known social bash. it clears the horizon by just a few degrees in the southern Mediterranean and is just visible at sunset during March in places such as Los Angeles, Gibraltar and Tokyo.
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Today it still helps with navigation, helping interplanetary probes arrive at their correct destinations as they use Canopus as a guide star.
From southern Victoria, including Melbourne, it is ”circumpolar”, meaning it never sets below the horizon. in March at sunset it is at its highest position for us, shining with a strong creamy-white hue, some 75 degrees up from the southern horizon. Conversely, six months from now, in September, it will be at its lowest point in the sky, teasingly flirting with the horizon without consummating the relationship.
Canopus is unmistakable, as only Sirius outshines it. but this has not always been the case. until about 90,000 years ago, Canopus was the brightest star in Earth’s night sky but Sirius, in its orbit around the galaxy, drew closer to us and hence unseated Canopus from the coveted pole position. However, in another 480,000 years it will once again be numero uno, as Sirius’s orbit takes it away from us.
Canopus is an F-type supergiant about 310 light years from the solar system. it is the most luminous object within a radius of 700 light years. it has a diameter that is 65 times larger than the sun’s and shines with an astonishing 13,600 times the luminosity of it.
In fiction, you’ll find it in Frank Herbert’s Dune, where the planet Arrakis is the third planet in orbit around Canopus. You can find it for real if you look high in the south tonight.
Follow Perry Vlahos on Twitter @perryastronomy.