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

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

   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 closer to Earth
   • E is far larger, with much more surface
   • E is younger, earlier on its path
   • E is much hotter
5. 4.

   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?

   • 16 times
   • 2 times
   • 4 times
   • 8 times
6. 5.

   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 age, since stars slide along the band
   • Its color, which changes each year
   • Its distance from Earth
   • Its mass
7. 6.

   When the Sun leaves the main sequence, which way will its dot move, by Pia's reading?

   • Up and to the left, toward the blue stars
   • It stays in the same spot
   • Up and to the right, toward the giants
   • Down along the band to the red dwarfs
8. 7.

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

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

9. 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

10. 8.

    Star A has a brightness of 10,000 and Star B 25. How many times brighter is A, by Tala's math?

    • 40 times
    • 400 times
    • 4,000 times
    • 9,975 times
11. 9.

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

    • 100 steps
    • 1 step
    • 2 steps
    • 99 steps
12. 10.

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

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