Canis Major

The patterns of the rising and setting Sun, Moon and the stars played a central part in astronomy since the beginning of time. As man gazed and studied upon these stars, it was only a natural tendency to make patterns out of them. They connected the brightest stars into figures, naming them after anything that seemed important to them. These are constellations and the names of these constellations had a strong cultural bias. For example, one constellation of seven stars is seen as a wagon, a great bear, a leg of an ox, a funeral procession, a minor government official, and a big dipper, depending on the different cultures. Despite the different interpretations, in the case of most constellations, the cultures made the same grouping of stars. For many of the ancient astronomers, they used the stars as a calendar, predicting the seasons. The Egyptians produced a 365-day calendar based largely upon when Sirius could first be seen rising before the Sun at dawn. Sirius is the brightest star of the sky making up the constellation Canis Major.

Canis Major is visible in the Northern hemisphere between December and March and visible in the Southern hemisphere between November and April. This constellation is lying mainly just south of the Milky Way. Extending the line formed by Orion's belt, (another constellation seen in the same season as Canis Major), 20 degrees down to the left leads directly to Sirius. This star is the head of the constellation Canis Major. This constellation consists of many stars, the three brightest stars being Sirius, Adhara, and Mirzam.

Sirius has a magnitude of 1.45. It is the brightest star in the sky based on two factors. The first being it's distance from the earth. This star is 8.7 light years away making it the second nearest of all the stars visible to the naked eye. Secondly, its luminosity is about 30 times that of the Sun. It has a mass of about 2.4 times greater than the sun, with a diameter nearly twice that of the Sun, and a higher surface temperature. Sirius also has a companion nearly 2 to 11 seconds of arc away from each other. It is 1/10,000 as bright as Sirius, having a mass of nearly 250,000 times and a diameter three times that of Earth's.

In 1844, F. W. Bessel was observing the motion of Sirius and discovered that the motion was not rectilinear but oscillating periodically about a mean position. He deducted that the motion of the star must have been influenced by another heavenly body of considerable mass. In 1862, Alvan Clark discovered Sirius' companion visually when he was testing a new telescope. He noticed that since it was a small and very faint star, and is relatively close to us, it could not be very luminous. Hence, it was thought that this star was of low temperature, and therefore a red star. However, in 1915 W. S. Adams discovered that the whole surface of the star is very luminous. Since it appears so faint it must be a very small star. This classified Sirius' companion as a white dwarf.

Sirius has always had a significant importance in the past. The Ancient Egyptians studied Sirius' motion across the sky in order to predict when the Nile would overflow. As the days became longer, the Nile would overflow its banks and supply water and fresh soil to the ground, which allowed them to grow their crops. Being able to predict when the Nile would overflow became a vital concern to them. Their priests eventually noticed that when a very bright star would rise concurrently with the Sun, the could expect the river to overflow within a matter of days. After 365 days, this star would rise concurrently with the Sun again, producing another new year. Thus, the calendar was born.

The ancient Egyptians built huge temples with long narrow corridors directed to the exact spot where Sirius would appear, just a little south-east than the Sun. These dark corridors eliminated most of the light of dawn and enabled the priests to see Sirius more clearly. Over prolonged observations, they came to realize that Sirius and the Sun would rise concurrently every 365 1/4 days. If they setup a calendar with only 365 days, they could not give accurate predictions in the future. In 100 years the Nile would rise 25 days later than expected. In order to correct this error, they would have to add one day every fourth year, making predictions more accurate.

The ancient Egyptians told this story in their mythology. Sepdet, their goddess, appears to them each year as the dog-star, Sirius. She disappears from the sky for several months of summer, when the Nile is low at ebb. When she reappears just before dawn, the Nile would begin to rise a few days later. She was thought of calling back the waters into the fields, arriving midway between summer solstice and autumnal equinox.

Sirius is also called the Big Dog Star since it belongs to Canis Major, who is seen as belonging to the Hunter, Orion. Orion, in Greek mythology, was a giant of Boeotia. He is famous for his beauty and hunting prowess. One day Zeus, Hermes, and Poseidan were travelling together on Earth. They were received by Hyrieus, and in gratitude for his hospitality, they promised to grant his deepest desire. Hyrieus wanted a son among anything else, and so nine months later Orion emerged from the ground. He had prodigious strength and was a passionate hunter. He followed his sport accompanied by his dog, Sirius.

There are many versions on how Orion died, however all of them are attributed to Artemis. Some of the stories include: she struck him down on the isle of Ortygis after Eos had carried him off; she shot him by accident at Apollo's instigation; she caused his death by a scorpion's sting after he had attempted to ravish her. After this, Orion descended into the realm of Hades, where armed with his brazen club continued to hunt the wild beasts. However, the most popular tradition is that he was transported into the sky where he shines brightly on the winter nights.

Constellations has played an important role in society since the beginning of time. Using the constellations to illustrate mythological lessons, or studying the stars to understand the Universe, man will continue to use the constellations as a history book. Everything we know today about our universe is based on our ancestors who studied the patterns in the sky leading to the creation of Astronomy. As we begin to learn more about our universe, exploring more of the unknown, we can look upon the constellations as a familiar reminder of our home.

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