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Stars


Contents

Ancient Astronomy and Constellations
Celestial Sphere
Star Magnitudes
Sky Charts
First Star
Hertzspung-Russell (HR) Diagram
Stellar Evolution
Brown Dwarfs
Variable Stars
Red Giants
Supergiants
Planetary Nebulae and White Dwarfs
Novae
Wolf-Rayet Stars
Supernovae, Neutron Stars, and Pulsars
Quark Stars
Preon Stars
Stellar Black Holes
Black Stars
Electroweak Stars
Stellar Models

Ancient Astronomy and Constellations

Stonehenge Ancient Observatory The Stonehenge (Figure 08-01a) is possibly the oldest astronomical instrument. It was built around 1500 BC outside Salisbury, England to track the movement of the sun and mark the solstice. The first record of a total eclipse of the sun was made in China as early as 899 BC. Figure 08-01b is the 13th-century Beijing Ancient Observatory - one of the most advanced facilities in the pretelescopic era. Modern astronomical instrument was first constructed by Galileo Galilei (1564-1642). He used a 30X telescope from lenses made by himself to draw a picture of the

Figure 08-01a Stonehenge
[view large image]


Figure 08-01b Ancient Observatory [view large image]

moon. He also discovered sun spots and Jupiter's 4 satellites. More detailed description of the instruments used by astronomers today can be found in the appendix: Astronomical Instruments.
The ancient astronomers divided up the starry sky into patterns, or constellations (see Figure 08-01c), which they named after personalities and creatures from their mythologies. The Greek astronomer Ptolemy, in the 2nd century A.D., listed 48 constellations (Figure 08-01d), the names of which are still in use today. Some of the configurations such as Scorpius and Southern Cross are rather obvious. Others such as the Great Bear and Pisces request a lot of imagination to figure out. City light may actually help to bring out the shapes better because of less distraction from the dimmer stars. Although the stars that make up a constellation appear relatively close together in the sky, they are not, in general, physically close in space. The constellations are now used to locate the
Constellations Constellation Name general direction of an object on the celestial sphere (see Figure 08-01e). To bring order from the chaos of naming stars, around the year 1600 Johannes Bayer, in what is now Germany, applied lower case Greek letter names to the stars more or less in order of brightness, rendering the brightest star in a constellation "Alpha", the second "Beta", and so on. To the Greek letter name is appended the Latin possessive form of the constellation name. Thus the brightest star in Orion is Alpha Orion, which is also known as Betelgeuse.

Figure 08-01c Constalla- tions [view large image]

Figure 08-01d Constallation Names [view large image]

See "The Constallations" (access from "The Main Menu") and "The Constellations and their Stars" for more information on the subject .

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