Read a Hertzsprung-Russell diagram

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   H-R diagram with the main sequence, giants, supergiants and white dwarfs shaded.

2. 1.

   NASA's example: a star at about 3,700 K with a brightness of about 0.1. Where does it plot, and what is it, by Esme's reading?

   • A hot star, since red means hot
   • Lower right of the main sequence: a cool red dwarf
   • Top right: a red supergiant
   • Lower left: a white dwarf
3. 2.

   A star is 25,000 K with a brightness of 0.05. Where does it plot, and why, by Jun's reading?

   • On the main sequence beside the Sun
   • Bottom left: a white dwarf, hot but tiny
   • Bottom right: a red dwarf, since it is dim
   • Top left: a blue giant, since it is hot
4. 3.

   H-R diagram with the giants shaded at the top right. Luz's friend says brighter stars on an H-R diagram are always hotter. Which response is best?

   • Disagree: dimmer stars are the hotter ones
   • Agree: the brightest stars are on the right
   • Agree: a star's brightness comes from temperature alone, not its size
   • Disagree: red giants are cool but bright because they are huge
5. 4.

   Main-sequence band with dots labeled by mass. Milo's cousin says stars move along the main sequence as they age, from blue to red. Which response is best (NASA)?

   • Disagree: mass sets its spot, and it leaves the band when core hydrogen runs out
   • Agree: the Sun was once a blue main-sequence star
   • Agree: blue stars age into yellow, then red ones
   • Disagree: stars do not change
6. 5.

   Row of star dots from blue on the left to red on the right. Noah's friend says blue stars must be cool, like the blue cold circle on a sink. Which response is best?

   • Disagree: blue stars are the hottest, red the coolest
   • Disagree: a star's color has no link to its temperature
   • Agree: red stars are hottest, like the hot tap
   • Agree: blue means cold
7. 6.

   Two stars both have a brightness of 100. One is 15,000 K and the other 4,000 K. Which is larger, by Pia's reading?

   • The hotter star, since it sits to the right
   • They are the same size
   • The 4,000 K star
   • The 15,000 K star, since hotter means bigger
8. 7.

   Star X has 4 times the Sun's radius and the Sun's temperature. Star Y has half the radius and twice the temperature. Which is brighter (brightness = radius² × temperature⁴), by Ren's math?

   • X, 4 against 2
   • Y, since it is hotter
   • X, 16 against 4
   • They are equally bright
9. 8.

   On the H-R diagram's brightness axis, one star sits 3 gridlines above another. How many times brighter is it, by Tala's math?

   • 30 times
   • 1,000 times
   • 300 times
   • 3 times
10. 9.

    H-R diagram of a cluster: the top left of the main sequence empty, the bottom right full. In a cluster whose stars formed together, the hot blue main-sequence stars are gone but the red dwarfs remain. Why, by Zee's reading (NASA)?

    • Red dwarfs use fuel the fastest
    • Massive blue stars used fuel fastest and left first
    • The blue stars aged into red dwarfs
    • Blue stars are the youngest and have not formed yet
11. 10.

    H-R diagram with the Sun's dot and four path sketches. The Sun will go from the main sequence to a giant, then to a white dwarf. Which path will its dot trace, by Ari's reading?

    • Up and right, then down and left
    • Straight up, then straight down
    • Up and left, then down and right
    • Down along the main sequence, then off the bottom