Read a Hertzsprung-Russell diagram

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   On an H-R diagram, which side holds the hottest stars, by Ari's reading?

   • The bottom edge
   • The right side
   • The left side
   • The top edge
2. 2.

   What does the up-and-down axis of an H-R diagram show, by Bo's reading?

   • The star's age, as it travels up
   • Distance from Earth
   • Brightness compared with the Sun
   • Surface temperature

3. Read this first

   Model stars (model data; Sun values from IAU)

   Star	Surface temperature (K)	Brightness (Sun = 1)
   A	30,000	10,000
   B	9,900	25
   C (Sun)	5,800	1
   D	3,500	0.01
   E	3,600	100,000
   G	20,000	0.01

4. 3.

   Star A is 30,000 K and Star D is 3,500 K. Which one sits farther left on the H-R diagram, by Kira's reading?

   • A, the hotter star
   • D, the cooler star
   • Neither; they line up one above the other
   • D, since it is dimmer
5. 4.

   What do all main-sequence stars have in common, by Jun's reading (NASA)?

   • They share one surface temperature
   • They are the same age
   • They are near the end of their lives
   • They fuse hydrogen into helium in their cores

6. Model stars (model data; Sun values from IAU)

   Star	Surface temperature (K)	Brightness (Sun = 1)
   A	30,000	10,000
   B	9,900	25
   C (Sun)	5,800	1
   D	3,500	0.01
   E	3,600	100,000
   G	20,000	0.01

7. 5.

   Star E is 3,600 K with a brightness of 100,000. Which group is it in, by Luz's reading?

   • Red dwarfs, since cool stars are dim
   • Hot blue stars, top left
   • White dwarfs, bottom left
   • Supergiants, top right
8. 6.

   Star G is 20,000 K with a brightness of 0.01. Which group is it in, by Milo's reading?

   • Red dwarfs, since dim stars are cool
   • White dwarfs, bottom left
   • Blue main-sequence stars, since hot stars are bright
   • Supergiants, top right
9. 7.

   One red, one blue. Pia spots a red star and a blue star. Which has the cooler surface?

   • The blue star
   • The red star
   • Neither; color shows just size
   • The blue star, since blue looks cold
10. 8.

    Row of star dots from blue on the left to red on the right, with 5,800 K marked. The Sun's surface is about 5,800 K. Which color class fits it, by Ren's reading (NASA calls it a yellow dwarf)?

    • Red, the coolest
    • Yellow, between the blue and red stars
    • Green
    • Blue, the hottest

11. Model stars (model data; Sun values from IAU)

    Star	Surface temperature (K)	Brightness (Sun = 1)
    A	30,000	10,000
    B	9,900	25
    C (Sun)	5,800	1
    D	3,500	0.01
    E	3,600	100,000
    G	20,000	0.01

12. 9.

    Star B has a brightness of 25. Compared with the Sun, it is what, by Tala's reading?

    • 25% as bright
    • 2.5 times brighter
    • 25 times brighter
    • 25 times dimmer
13. 10.

    Star D has a brightness of 0.01. Compared with the Sun, it is what, by Esme's reading?

    • 100 times brighter
    • 10 times dimmer
    • 100 times dimmer
    • 0.01 times hotter