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Stars . How Stars are Classified. How bright a star looks depends on two factors: its magnitude, or brightness, and its distance from Earth. Two important terms to remember are: apparent and absolute magnitude.
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How Stars are Classified • How bright a star looks depends on two factors: its magnitude, or brightness, and its distance from Earth. • Two important terms to remember are: apparent and absolute magnitude. Apparent magnitude is how bright a star seems to be and Absolute magnitude is how bright it really is.
Types of Stars • The color of a star tells us about its surface temperature: Blue:These stars have the hottest surface temperature. Red:These stars have the coolest surface temperature. Astronomers use surface temperatures and absolute magnitudes to classify stars.
The following diagram shows the relationships between size, magnitude, temperature and color. The absolute magnitudes of stars are plotted from bottom to top. • The brightest stars are at the top. The surface temperature of stars are plotted from right to left. The hottest stars are on the left. The color is shown by its background color. The size is shown by its relative size on the diagram.
Life cycle of a star 1.Nebula: A star begins within a huge cloud of hydrogen, helium and tiny particles of dust. 2. Protostar: After million of years, the particles begin to squeeze together, it grows in mass and its temperature rises. 3. Main-Sequence star: After several million years, the temperature at the center reaches about 15 million °c. 4.Expanding star: A star like the sun shines for about 10 billion years before its hydrogen runs low. 5.Red Giant: The star may expand to 100 times its original size. 6.Planetary Nebula: The red giant’s atmosphere expands a million times. 7.White Dwarf: The star continues to shine dimly for billions of years until it runs out of energy.
Observing Stars • Scientists learn about stars by studying the energy they send into space. • Each kind of wave carries a different amount of energy. The waves range from high-energy X rays to low-energy radio waves. • Astronomers use different kinds of telescopes to detect each kind of wave.
Each wave of energy gives scientists information about the object it came from. • This is how scientists know that the sun and most other stars are mostly hydrogen and helium.
REVIEW ( Please use the mouse for the review section…) 1. What is absolute magnitude? It’s the amount of energy the sun produces. How bright a star really is. A B How bright a star seems to be. None of the above C D
REVIEW ( Please use the mouse for the review section…) 2. What is apparent magnitude? It’s the amount of energy the sun produces. How bright a star really is. A B How bright a star seems to be. None of the above C D
REVIEW 3. What name is given to the last stage in the life cycle of a star? Nebula Red giant A B None of the above C Protostar D
That is CORRECT! The name of the last stage is: WHITE DWARF
Works Cited… • www.office.microsoft.com/clipart • Harcourt Science Texas Teacher’s Edition.