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Some Basic Facts on Constellations
A constellation is a group of stars that forms a regular pattern in the sky. These patterns stay the same during the lifetime of a person and change only after several thousands of years. Depending on the season and the latitude, different constellations may be visible in the sky. During the night you will also notice that the constellations move across the sky from the east to the west, and this is due to the movement of the Earth. The stars that form a constellation may be many light years away from each other.
The number of constellations is officially 88. Some of them are bright and easy to spot, while others are fainter and harder to locate in the night sky. Constellations are very useful for navigational purposes as they are considered to be the "landmarks" of the sky.
The left image was taken by Hubble telescope and shows Sirius A and the smaller Sirius B. Both stars form a binary system and belong to the constellation of Canis Major. The right picture is an artist's impression of the two stars. Sirius B is more discernible.
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Tips on How to Identify the Constellations
- The right way to start observing the sky is to locate the most discernible constellations at first. It would be better to start with the BiGreat Bear or Orion, in the case of the northern hemisphere. Both are very easy to locate in the sky, since their shapes are very distinguishable and their stars very bright.
- Identifying one or two constellations each night is a satisfactory progress. The next night you may try to locate a neighboring constellation.
- Begin with the brighter constellations. These will actually guide you to locate the dimmer ones.
- Each night you should spot the constellations previously learned, and then add one or two new ones. That way you will be accustomed to their shapes and will detect them more and more easily.
- When trying to identify constellations in the night sky, the use of binoculars or telescope is not very helpful. The idea here is to observe a wide area of the sky and not a narrow part of it. However, you can use either of them if you want to observe a star, deep sky object etc.
- The best time for gazing at a particular constellation actually depends on your latitude (southern or northern hemisphere) and the time of year. Some of them are never visible to the hemisphere that you live (e.g. the Centaurus constellation is only visible in the southern hemisphere).
- The best place to be when gazing at the sky is far away from any artificial light. A rooftop would also make a nice place in case you don't live in the country.
- Keep in mind that different constellations are visible depending on the latitude and the time of the year. A sky guide would be very helpful in this case.
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Basic Guide for the Brightest Stars and Constellations of the Northern Hemisphere
One of the most easily detectable constellations in the northern sky is the Great Bear (or Ursa Major, or Plough). The constellation looks like a saucepan and is close to another pan-like constellation, the Little Bear or Ursa Minor. According to the Greek mythology, Zeus fell in love with a huntress named Callisto. Zeus' wife, Hera transformed Callisto into a bear. In order to save Callisto from being hunted by her own son Arcas, Zeus decided to transform Arcas into a bear as well, and then place them both among the stars to be safe.
The Great Bear can be used to locate the North Star which lies just above the North Pole. The North Star is very important as far as navigation is concerned and is often used as a reference point by sailors. In order to see the North Star, you can draw a line connecting the two stars at the bottom of the "pan" and then multiply this distance by five. Your eyes will then arrive at the North Star which always stays at the same spot.
The most impressive constellation of the northern sky is Orion, also known as the "hunter". Orion actually resembles the figure of a hunter with a very distinctive line of stars in the middle also known as the Orion's belt. This is a very characteristic formation and is often used to locate other constellations. For example, after locating Orion's belt, you can easily see Betelgeuse, which lies on Orion's left shoulder. A little above Orion's shoulder at the north-west, you may see two bright stars Castor and Pollux, belonging to the Gemini constellation. The two stars represent the heads of the twins that Zeus took pity on, after one of them was killed. He gave them a place in the heaven so that they would never miss one another.
If you draw a line from Orion's belt to the bottom left of the constellation, you will be able to see Sirius, the brightest star of the sky, which is actually a binary system. Sirius belongs to the constellation of Canis Major and is also known as the Dog Star. According to the myth, Sirius was actually one of Orion's hunting dogs, who was accidentally killed by Artemis.
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- commons.wikimedia.org: Orion Constellation
- commons.wikimedia.org: How to Locate Sirius
- commons.wikimedia.org: The Gemini Constellation
- nasaimages.org: Orion Stars
- nasaimages.org: Constellations of Great and Little Bear
- nasaimages.org: Sirius A and B. The Photo was Taken by Hubble Space Telescope
- nasaimages.org: Binary System of Sirius A and Sirius B