Star Properties

Two stars are the same distance from Earth. One is larger than the other. How do the brightness and temperatures of the stars differ with size?

• The smaller star is fainter and cooler

• The smaller star is brighter and hotter.

• The larger star is brighter, but not necessarily hotter.

• The larger star is cooler, but not necessarily brighter.

Which physical property of a star is an indicator of its

temperature?

• mass

• color

• brightness

• distance from Earth

Which properties would be most useful for the classification of a star recently discovered by an astronomer?

• temperature, solar flare activity, number of surrounding

  planets, and size

• temperature, size comparison to our sun, solar flare activity,

  and luminosity

• apparent magnitude, temperature, luminosity or absolute

  brightness, and size

• apparent magnitude, temperature, distance from the Milky Way, and presence of dark spots

Which physical property is the brightness of a star as seen from

Earth?

• apparent magnitude

• radiation zone

• temperature

• color

Stars can be organized by size and temperature into four groups: dwarf stars, main sequence stars, giant stars, and supergiant stars. Into which group does the Sun most likely fall?

• dwarf stars, because the Sun is much smaller than most other

  stars

• giant stars, because the Sun is much larger than most other

  stars

• main sequence stars, because the Sun is of average size

• 
  

  supergiant stars, because the Sun is one of the largest stars

The brightness of a star as seen from Earth is its apparent magnitude. How is apparent magnitude different from absolute magnitude?

• Apparent magnitude depends on the size of a star; absolute magnitude does not.

• Apparent magnitude depends on the color of a star; absolute magnitude does not

• Apparent magnitude depends on the temperature of a star; absolute magnitude does not.

• Apparent magnitude depends on the distance of a star from Earth; absolute magnitude does not

Star

TemperatureStar Temperature (Kelvin)

Alpha Centauri B 5,300

Proxima 2,700

Sirius A 9,000

The Sun 5,800

Which star listed in the table appears the reddest?

• Alpha Centauri B

• Proxima

• Sirius A

• The Sun

Star Name Color Apparent Magnitude

Approximate Distance From Earth

(light years)

Rigel Blue 0.18 770

Vega White 0.03 25.3

Arcturus Orange -0.05 36.7

Betelgeuse Red 0.45 430

Polaris Yellow-white 1.97 430

Suppose you knew the surface temperature of Polaris. Which star would you expect to have a temperature most similar to that on Polaris?

• Vega

• Regel

• Betelgeuse

• Arcturus

Main sequence stars appear as a band on Hertzsprung-Russell (HR) diagrams. The HR diagram below shows the relationship between absolute brightness and temperature. Absolute brightness is measured here using a brightness scale, called absolute magnitude.What is the relationship between a star’s absolute brightness (measured as absolute magnitude) and its temperature?

• The lower the temperature, the brighter the star.

• The higher the temperature, the brighter the star.

• Most stars have the same temperature, but differ in absolute

  brightness

• Most stars have the same absolute brightness, but differ in

  temperature.

The Sun is classified as a "G" main sequence star. The Hertzsprung-Russell diagram indicates that, because the Sun is a "G" main sequence star, its surface temperature is

• between 6,000 K and 8,000 K.

• between 4,000 K and 6,000 K.

• greater than 10,000 K.

• less than 4,000 K.