Name ________________________________________                Date ____________

Period _______

 

Notes on Stars

                                                                                                        Answer Key

Color and Temperature pg. 590

 

  1. Relate the temperature of a star to its color.
    1. The coolest stars are 2,800° C and appear red.  The hottest stars are 28,000°C or higher and look blue.  The sun, a yellowish star, has a temperature of 5,500°C at its surface.  Stars a little cooler than the sun appear orange.  Stars a little hotter than the sun are white.

 

  1. We use the Kelvin Scale often to express the temperatures of stars (symbol K).  The equation from Celsius to Kelvin is: K=C+273.15.  Knowing this equation, what is the temperature of the sun in degrees Kelvin?
    1. 5, 573.15 K

 

Distance of Stars pg. 591

            Use figure 25.8 and the text

 

  1. What is parallax?
    1. The apparent change in the position of an object caused by a change in the position of the observer.

 

  1. Why do nearby stars appear to change position when observed from Earth?
    1. Because of the Earth’s movement around the Sun.

 

  1. Would a star closer to Earth have a larger or smaller parallax than the star show here (in Figure 25.8)?
    1. Larger

 

  1. Why isn’t the apparent brightness of a star a good measure of its distance from Earth?
    1. Because a very bright, but distant, star could seem to be the same distance from Earth as a faint, but near, star.

Magnitude pg 592

 

  1. Using the data on the chart and the text, determine if the sun is a relatively bright star in terms of magnitude.
    1. Sun is a relatively cool star

 

  1. What is the difference between apparent magnitude and absolute magnitude?
    1. Apparent Magnitude:  a stars brightness as it appears from Earth

Absolute Magnitude:  a stars actual brightness

 

 

 

 

SkillBuilder pg 592

            Use the information on the bottom of pg. 592

 

  1. How much larger than the sun is Polaris?
    1. Its mass is 14 times greater; Its diameter is 90 times greater

 

  1. Explain how mass and absolute magnitude are related.
    1. In general, as mass increases, so does absolute magnitude

 

  1. Explain how diameter and absolute magnitude are related.
    1. No relationship

 

  1. Which is most closely related to magnitude, mass or diameter?
    1. Mass

 

The H-R (Hertzsprung-Russel) Diagram pg. 593

            Use figure 25.9 and the text

 

  1. What determines a star’s position on the H-R diagram?
    1. Average surface temperature and absolute magnitude

 

  1. Into what group do most stars fall?
    1. Main-sequence group

 

  1. In main-sequence stars, what is the relationship between magnitude and temperature?
    1. Hotter stars are brighter

 

  1. What are the characteristics of supergiants?
    1. Bright, cool to medium hot

 

  1. Which stars are relatively hot but dim?
    1. White Dwarfs

 

  1. What is the approximate temperature range for red giants?
    1. 3,000-5,000 °C

 

  1. How would you compare a red giant to the sun in terms of magnitude and temperature?
    1. A red giant is much brighter and cooler than the sun