Unit 2 Lesson 2 - Stars

Unit 2 Lesson 2 - Stars

by Sharon Holtom

​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.

Multiple Choice

The hottest stars are

• white

• blue

• red

• yellow

​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

Open Ended

Describe the way in which astronomers measure luminosity

Multiple Choice

Two stars have the same apparent magnitude as seen from Earth's surface. Star A is 33 ly away. Star B is 346 ly away. Which claim is true?

• Star B is larger than Star A

• Star B is more luminous than Star A

• The stars have the same absolute magnitude

• Star A has a smaller absolute magnitude

Open Ended

Compare the size of the sun to the size of other stars

Open Ended

Describe the way in which astronomers measure the brightness of stars

You are finished with Lesson 2

Multiple Choice

Which of the following units is used to express the size of stars?

• kilometer

• light-year

• solar radius

• astronomical unit