The winter skies are filled with many bright stars, and the brightest star of all, Sirius, is one of them. The constellation represents one of the two hunting dogs of the hunter Orion. Canis Major may be chasing the hare, Lepus, through Orion's legs. Or he might be helping Orion battle Taurus, the celestial bull. You can locate Sirius by tracing Orion's Belt to the left.
SIRIUS: Sirius is the brightest star in all the skies, with a magnitude of -1.5. Sirius is not the largest star in the heavens, only about twice the diameter and mass of our sun. Its brightness is contributed by its proximity to our solar system, only 8.7 light years away. Thus it outshines bigger stars like Betelgeuse in Orion, which is further away. Sirius is the seventh closest star to us.
The name Sirius comes from Greek, meaning searing or scorching. It was named this way because it was thought Sirius was a source of heat. For in the early days of August in ancient times Sirius rose just before sunrise. So the Greeks thought the combined heat of the sun and the sun caused the sweltering "dog star days" of summer. It was later shortened to the "dog days". Due to the slow, slow movement of every star though the sky, Sirius now rises before sunrise in late August.
Sirius also has white dwarf companion star, nicknamed the Pup. This comrade is only about 2% of the suns surface, around twice the size of the earth. But it is still hotter than the suns surface and has the same mass of it. If just a spoonful of this star were on earth, it would weigh many tons. White Dwarfs are the dying remnants of stars like the Sun. The Pup orbits Sirius A once every 50 years. It is hard to separate the two stars unless you have a pretty large scope.
ADHARA and MURZIM: Also known as Mirzam, but both are from Arabic for "the Announcer". This is because when it rises, Sirius will soon rise too. Mirzam is a 2nd magnitude blue giant star about 850 light years away. Adhara is the 22nd brightest star in the sky, at mag. 1.5. Adhara is also a blue giant, and has a 8th magnitude companion.
WESEN and ALUDRA: Wesen is Arabic for weight, but the meaning behind the name is lost to us. But the name still fits, for Wesen is a supergiant, it is 20 times the mass of the sun. I gives off 100,000 times as much light as the Sun, so it appears of magnitude 1.8 despite its considerable distance of over 2000 light years. Aludra is another supergiant star that are plentiful in the Canis-Orion section of the sky. It is mag. 2.4 and is 2700 light years away. If Wesen or Aludra were as close to us as Sirius is, they would shine as bright as a half moon. Conversely, if Sirius were as far away as Wesen, then it would be 11th mag., way below naked eye visibility.
MULIPHEN, FURUD, and OMICRON (o) 2: Muliphen is a mag. 3.8 giant star. Even though Muliphen is designated Gamma Canis Major. It is much fainter than the stars designated Delta (Wesen), Epsilon (Adhara), Zeta (Furud), and Eta(Aludra). It was said that it entirely disappeared in 1670, and was not observed for 23 years. After it reappeared it has maintained a steady brilliance, although faint for it lettering. Furud is a 2.4 mag. star with a spectroscopic binary companion. It is about 390 light years away.
M41: M41 is a globular cluster that can be seen naked eye under good conditions. It was mentioned by Aristotle about 325 B.C. as one of the "mysterious cloudy spots" then known in the sky. M41 has about 50 stars, and the brightest is a 7th magnitude orange giant. With binoculars you can pick out the brightest members of the cluster. A small telescope will reveal more. Low magnification is needed to fit the cluster into the field of view.
NGC 2362: NGC 2362 is a star cluster that surround the star Tau (t) Canis Major. This cluster is one of the younger star clusters. In very small scopes the cluster appears to be a nebulosity around Tau. But any scope bigger than then 2 inches should resolve the stars.
MYTHOLOGY: Sirius was placed in the sky after his
master, Orion, was killed by Scorpius the Scorpion. He is faithfully helping
his master hunt his prey, the hare and the bull. To the Egyptians Sirius
heralded the annual flooding of the
Canis Major may also represent another two-headed dog called Orthrus. This was Geryon's watchdog; his job was to guard the tyrant's cattle. When Hercules had to capture the cattle as his tenth labor, he had to kill Orthrus.
Written and illustrated by Nik Aiavaliotis
Published by El Valle Astronomers. Lee Mesibov, President. 505-579-4604.