Read a Hertzsprung-Russell diagram

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   A star is 4,500 K with a brightness of 100. Which kind of star is it, by Bo's reading?

   • A giant: cool but bright
   • A main-sequence star like the Sun
   • A hot blue star, since it is bright
   • A white dwarf

2. 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

3. 2.

   Star A is 30,000 K with a brightness of 10,000. Which kind of star is it, by Esme's reading?

   • A red supergiant
   • A red dwarf
   • A hot, blue main-sequence star
   • A white dwarf, since it is hot
4. 3.

   A star is 6,000 K with a brightness of 1.2. Where does it sit, by Jun's reading?

   • Among the white dwarfs
   • Among the supergiants
   • Among the blue stars, since 6,000 K is very hot
   • On the main sequence, near the Sun

5. 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

6. 4.

   Stars D (3,500 K) and E (3,600 K) have nearly the same temperature, but E is 10 million times brighter. Why, by Kira's reading?

   • E is far larger, with much more surface
   • E is much hotter
   • E is younger, earlier on its path
   • E is closer to Earth
7. 5.

   Two stars have the same temperature, but one has twice the radius. How many times brighter is it (brightness grows as radius²), by Luz's math?

   • 4 times
   • 2 times
   • 16 times
   • The same, since temperature is the same
8. 6.

   Two stars are the same size, but one is twice as hot (in kelvins). How many times brighter is it (brightness grows as temperature⁴), by Milo's math?

   • 4 times
   • 8 times
   • 16 times
   • 2 times
9. 7.

   Main-sequence band with dots labeled by mass. What mostly decides where a star sits on the main sequence, by Noah's reading (NASA)?

   • Its color, which changes each year
   • Its age, since stars slide along the band
   • Its distance from Earth
   • Its mass
10. 8.

    After its giant stage, the Sun becomes a white dwarf. Where will its dot be, by Ren's reading?

    • Back on the main sequence
    • Bottom left
    • Top left
    • Bottom right, since it will be dim

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.

    How many ×10 gridline steps are there from Star D (0.01) up to the Sun (1), by Zee's count?

    • 2 steps
    • 99 steps
    • 1 step
    • 100 steps
13. 10.

    How many ×10 gridline steps is Star E (100,000) above the Sun (1), by Ari's count?

    • 4 steps
    • 100,000 steps
    • 50 steps
    • 5 steps