Intro to Constellation (2) Canis Major

Today, let us learn something about Canis Major.

Name: Canis Major

Abbr: CMa

Chinese Name: 大犬座

Brightest Star: Alpha Canis Majoris / Sirius (-1.46 m)

Visibility: 60 N to 90 S, prime in February

Canis Major, the Great Dog, is a constellation in the southern celestial hemisphere. Sirius, the brightest star in the night sky, is in this constellation. Ancient Babylonians thought that the southern stars of Canis Major resembled a bow and Sirus was the arrow aiming towards Orion.

Ancient Greek believed that Canis Major represented Laelaps, a mythological dog that never failed to catch its prey. In a story, it was asked to catch the Teumessian fox, a fox that could never be caught. The chase would go on forever if Zeus had not cast them into stars. Laelaps became Canis Major and the fox became Canis Minor.

In Chinese astronomy, the majority of Canis Major belongs to the Vermilion Bird (南方朱雀).

Notable Stars

Not surprisingly, Sirius is the star featured today. At a distance of 8.6 light years, it is one of the nearest neighbors of the Earth and has a visual apparent magnitude of -1.46. Usually, it is fainter than Jupiter and Venus, but can be as bright as Mercury or Mars. Sirius will continue to be the brightest in the next 210,000 years until it gets outshined by Vega.

Sirius is a binary star consisting of Sirius A and Sirius B. Sirius A is 10,000 times brighter than Sirius B. Hundreds of millions of years ago, both the two stars were bright bluish stars. Around 120 million years ago, Sirius B collapsed into a faint white dwarf.

Sirius has a special significance in different cultures. Its heliacal rising at Cairo reflects the onset of the annual flooding of the Nile. Ancient Greeks thought that the appearance of Sirius as the morning star is the prelude to the hot and dry summer. The twinkling of Sirius, varying from red, white, and blue, meant malignant influence to Greek observers. For Polynesians, the star was an important reference for their navigation on the Pacific Ocean.

The Voyager 2 spacecraft, may pass within 4.3 light-years of Sirius in around 296,000 years.

(Chinese Astronomy)

天狼星，夜空中最亮的星。中国古代观星者的眼里，天狼星的南边是弧矢，有着弧矢射天狼一说。天狼星往往被赋予掠夺和侵略的意味，我们在不少诗词中都能发现它。比如苏轼的《江城子·密州出猎》。

老夫聊发少年狂。左牵黄，右擎苍。锦帽貂裘，千骑卷平冈。为报倾城随太守，亲射虎，看孙郎。 酒酣胸胆尚开张。鬓微霜，又何妨。持节云中，何日遣冯唐。会挽雕弓如满月，西北望，射天狼。

Notable Systems And Objects

There are 7 star systems that have planets. NGC 2207 and IC 2163 are two interesting galaxies. They are a pair of colliding spiral galaxies about 80 million light-years away.

The two are only in the first step of colliding and merging. They are expected to merge and become an elliptical galaxy or a disk galaxy in about a billion years.

Credit

Most of the contents are summarized from Wikipedia. You can click the images to reach the source websites.