Sirius, the sky's brightest star
How to See It
Sirius is the jewel of the winter and spring skies, nearly 3-and-a-half times brighter than Arcturus, the next brightest star easily visible from northern latitudes.
Although white to blue white in color, it would not be unreasonable to call Sirius the rainbow star, as it often flickers with many colors.
The brightness, twinkling and color changes sometimes prompt first-time observers to report Sirius as a UFO. But these changes have nothing to do with Sirius. Rather, they are the result of variations in the earth’s atmosphere. The light from Sirius, which always appears fairly low in the sky from the mid-north latitudes, passes through a long column of air before it reaches our eyes. Changes in density and temperature of this air affect the light and cause the behavior we see. This happens for other stars, too, but it is more noticeable for Sirius because it is so bright, and because it appears low in the sky.
Sirius is a star best seen in the evening skies of winter through mid-spring. From the mid-northern latitudes such as most of the U.S., it rises in the southeast, crosses low to the south, and sets in the southwestern sky. It rises by mid-evening in December, and by mid-April it is setting in the southwest at about the same time. Although it is easy to find because of its brilliance, anyone familiar with Orion can simply draw a line through Orion’s Belt, to the left. Sirius is roughly 8 times as far from the Belt as the Belt is wide from one side to the other.
History and Myth
Sirius has been known since ancient times, and its name signified its nature as “scorching” or “sparkling.” It was associated with the Egyptian god Osiris and other gods. Ancient Egyptians note that Sirius rose just before the Sun each year immediately prior to the annual flooding of the Nile River. Although the floods could bring destruction, they also brought new soil and new life. Fittingly, Osiris, whom Sirius may have represented, was a god of life, death, fertility and rebirth of plant life along the Nile.
Sirius is also frequently called the “Dog Star,” being the chief star in the constellation Canis Major, the Big Dog. Recalling its role in predicting Nile floods, Sirius is the dog in our phrase, “The dog days of summer.”
In India, Sirius is sometimes known as Svana, the dog of Prince Yudhistira. The prince and his four brothers, along with Svana, set out on a long and arduous journey to find the kingdom of heaven. However, one by one the brothers all abandoned the search until only Yudhistira and Svana were left. At long last they came to the gates of heaven. The gatekeeper, Lord Indra, welcomed the prince but denied Svana entrance. Yudhistira was aghast and told Lord Indra that he could not forsake his good and faithful servant and friend. His brothers, Yudhistira told the Lord, had abandoned the journey to heaven to follow their hearts’ desires. But Svana, who had given his heart freely, chose to follow none but Yudhistira. The prince told the Lord that without his dog, he would forsake even heaven. This is what Lord Indra had wanted to hear, and then he welcomed both the prince and the dog through the gates of heaven.
This X-ray image from Chandra satellite shows that the sky's brightest star - Sirius - is really two stars. The Sirius star system is located 8.6 light years from Earth. (NASA)
Science
Magnitude is a star’s brightness expressed by a number. The smaller the number, the brighter the star. The visual magnitude of Sirius is -1.44, lower than any other star. It is 3.5 times brighter than Arcturus in Bootes, the next brightest star easily visible from the northern hemisphere. There are brighter stars in terms of actual energy and light output, but they are farther away and hence dimmer. Normally, the only objects that outshine Sirius in our heavens are the sun, moon, Venus, Jupiter, Mars and Mercury (and frequently Sirius outshines the latter two!).
The next brightest star (Canopus) after Sirius, and the closest major star (Alpha Centauri) are both too far south in the sky to be easily seen from mid-north latitudes.
At 8.6 light years distance, Sirius is one of the nearest stars to us after the sun. (A light year is nearly 6 trillion miles!) In fact it is the nearest star easily visible to the unaided eye from most of the northern hemisphere. Classified by astronomers as an “A” type star, it is much hotter than our sun, with about surface about 17,000 degrees F (the sun is about 10,000 degrees F). With slightly more than twice the mass of the sun and just less than twice its diameter, Sirius still puts out 26 times as much energy. It is considered a normal (main sequence) star, meaning that it produces most of its energy by converting hydrogen into helium through nuclear fusion. As mentioned above, Sirius has a small, faint companion star appropriately called “The Pup.” That name signifies youth, but in fact “The Pup” is a dead star called a “white dwarf.” Once a mighty star, today it is an earth-sized ember too faint to be seen without a telescope.
HELLO. Iwould liki to ask ,is it that star which is known as SAGITOURIUS .
Nadeem,
No, Sirius and Sagittarius are not the same. Sirius is a star seen mostly in the evening sky of winter and spring (Northern Hemisphere). Sagittarius is a constellation, or group of stars, which is seen mostly in the evening sky of summer and fall (Northern Hemisphere). Interestingly, though, Sirius and Sagittarius are separated by about 12 hours in the sky, meaning that 12 hours after one appears (in the south, for example), the other other will appear in about the same place. They are not exactly opposite each other, but are best seen in opposing seasons. (Sirius is best in the early evening of early spring, whereas Sagittarius is best in the early evening six months later, in September.)
Larry Sessions
how many of our suns would fit inside the star sirius
Joseph,
It depends on what you mean. Let’s assume that both the Sun and Sirius are spheres. In reality, they aren’t. They are both “oblate spheroids,” but for our purposes it is OK to assume that they are spheres.
If you mean physically, how many spheres the size of our Sun would fit inside a sphere the size of Sirius, the answer is 1. Sirius is about 1.75 times the diameter of our Sun, and you simply could not fit more than one Sun inside Sirius.
However, if you mean how does the total volume of Sirius compare to the total volume of the sun, the answer is about 5.36. In other words, the volume of Sirius is about 5.36 times the volume of our Sun. This is because volumes vary by the cube of the radius. The radius of Sirius is about 1.75 times the radius of the Sun, and the cube of 1.75 is 5.359375.
I hope this helps.
Larry Sessions
Denver
thank you larry for responding back to me..the reason why i ask that question is i could of sworn i read that 100 of our sun can easily fit into the star sirius indicating how big the star sirius is bigger then our own sun
Joseph,
I suspect that you were thinking of another star, many of which are larger than Sirius. Betelgeuse, in Orion, for example, is about 600 times the radius of our Sun, meaning that 600 spheres the size of our Sun could fit, edge to edge, across the interior of a sphere the size of Betelgeuse (and a great many more besides). I don’t know the exact number right off because it involves something known as “packing density,” about which you can learn more here:
http://mathforum.org/library/drmath/view/55181.html
In terms of volume, Betelgeuse is 600 cubed times more voluminous than the Sun, which is 216 million times!
Larry S.