​Surface Temperatures

​Scientists use colors to identify the temperatures of stars.

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​The same way that metal changes from black to red to yellow to white as it gets heated, stars colors indicate how hot their surface is.

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​The H-M Diagram is used to classify them.

​Star Light, Star Bright

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​Apparent Magnitude

​Astronomers called the brightest stars first magnitude and faintest stars  sixth magnitude

• Today, faint stars have larger, positive numbers (magnitude +30) and brighter stars have smaller, even negative, numbers (brightest is -2)

• Our sun has a magnitude of -26.8 due to its nearness to Earth, although it is not as luminous as the brightest star

​Absolute Magnitude

​Luminosity is measured on the absolute magnitude scale

• It is determined by how bright a star would be if it were located at a standard distance

• Sun’s absolute magnitude is only +4.8

You are finished with Lesson 2