The very first article published on One-Minute Astronomer was about Sirius, the brightest star in the night sky.
So now, nearly three years later, it’s about time I got around to the second-brightest star, Alpha Carinae. Also known as Canopus, this star takes its name from a bit player in one of the earliest epics of western literature. And it embodies mystical properties of happiness and long life, according to ancient legends of the far East.
Canopus is the brightest star in the southern constellation Carina, the Keel. This whitish star lies just south of Sirius, and the two brilliant stars bejewels a splendid star in the southern Milky Way.
At a declination of about -52 degrees, Canopus never rises above the horizon for observers north of 38ºN latitude. But many northerners catch sight of it while travelling south for winter vacation. Almost directly south of Sirius, Canopus is just visible this time of year from southern Spain and Portugal, and from the southern United States. In the southern hemisphere, these two brightest stars are directly overhead in the evening summer sky.
This grand star shines with an apparent magnitude of -0.72, about half as bright as Sirius. But Canopus is intrinsically far brighter. If Canopus, which is 310 light years away, were moved to the same distance as Sirius, about 8.6 light years, it would shine… if I did my math right… with an apparent magnitude of -8.5. That’s bright enough to clearly see in daytime and cast shadows on moonless nights.
The star Canopus (bottom center), as seen from the latitude of Key West, Florida, at 10 p.m. local time (click to enlarge)
Canopus is classified as an F0 II giant star, and is likely fusing helium into carbon in its core. It has swelled to about 9/10 of Mercury’s orbit, and shines with the brightness of 13,000 Suns.
But Canopus still defies complete understanding. As far as astronomers know, it isn’t big enough to go supernova. Once it loses mass as a planetary nebula, the star will probably settle down for the next many billions of years as a slowly cooling white dwarf.
Since it’s a bright star off the ecliptic, away from the Sun and bright planets, Canopus often serves as a navigation star for many deep-space probes, which orient themselves relative to Canopus and other guide stars using star-tracking cameras and control systems.
Canopus takes its name from the pilot of the sea ship that carried the legendary Menelaus from Greece to Troy in an attempt to reacquire his beautiful wife, Helen, from the feckless Trojan prince Paris. Much bloodshed and misery ensued for good men, on both sides, as readers of Homer’s Odyssey well know.
But the Chinese have a different legend for this star. Though Canopus is only visible in southern China, and even there would be low on the horizon, shining with a reddened glow.
But red is the color of happiness and long life in China and other eastern cultures. That’s why Canopus is known as the “Star of the Old Man”, or the “Star of Old Age”. It’s supposed to bring good fortune to those who wish to enjoy the privilege of a long and happy life.
And I wish you exactly that, dear reader. Until next time…