A few are based on Greek or Chinese names. Most of the traditional names used today are based on Arabic star names. In addition to the Bayer designation, many of the brighter stars have also received traditional names over the years. This means than in some of the constellations the Bayer designations do not follow the star’s apparent magnitudes in order. As a result, the brightest star in each constellation did not always get assigned as Alpha. Stars were usually assigned to one of six magnitude classes. However, in Bayer’s day the brightness of a star could not be measured precisely. These classifications are known as Bayer designations and are still used today. The next brightest is Gamma Tauri, and so forth. For example, the brightest star in the constellation Taurus is Alpha Tauri. In most cases, Bayer assigned the letters in alphabetical order based on the star’s brightness. Each star’s name consists of a Greek latter plus the Latin name of the constellation in genitive, or possessive, form. Bayer assigned a lower-case Greek letter such as alpha, beta, gamma, etc. Most of the brighter stars in the constellations were assigned names by the German astronomer Johann Bayer in 1603, when he published his star atlas known as Uranometra. The stars in the constellations are classified using their apparent magnitude, also called visual magnitude. Apparent magnitude is the brightness of the star as it appears in the night sky from Earth. Absolute magnitude measure the brightness of a star as it would appear if it were placed at a fixed distance from the Earth. Astronomers use two different types of magnitude. Therefore, a magnitude 1 star is 2.5 times brighter than a magnitude 2 star, and is 2.5 x 2.5 times brighter than a magnitude 3 star. Each order of magnitude equals a variation in brightness of approximately 2.5 times. The magnitude of a star is measured on a logarithmic scale, similar to that used for measuring earthquakes. Stars in the night sky are classified by their brightness, which is referred to as their magnitude. The International Astronomical Union defined the final boundaries of the 88 constellations in the 1922. Lacaille created 14 new constellations while mapping the southern skies from an observatory in South Africa. Several more were added by the French astronomer Nicolas Louis de Lacaille in his catalogue published in 1756. Bayer added a total of 11 new constellations to the sky. They were charted by Dutch navigators in the late 16th century and included in Johann Bayer’s star atlas Uranometra in 1603. Some of the southern constellations are more recent because they could not be seen by any of the ancient civilizations north of the equator. They were based on the work of the Greek astronomer Eudoxus of Cnidus. The Greek astronomer Ptolemy cataloged 48 constellations in the second century. Many of these ancient constellations are associated with the rich mythology of the time. There are 50 constellations that date back to ancient Greece, Rome, and the Middle East. Ancient cultures in different parts of the world have assigned different patterns to these star groupings. Their origins date back hundreds or even thousands of years. The asterisms that make up the constellations were seen by ancient people as patterns in the stars.
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