How a star's mass decides its life

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Table, Five main-sequence stars, with columns Star, Mass (Suns)

   V, 0.5; W, 1; X, 5; Y, 12; Z, 30. Note: supernova above about 8 Suns (sources give 7 to 10); black hole from about 20 or more (sources vary).

2. 1.

   Which star in the table is most likely to leave a black hole, by Jun's reading?

   • W, at 1 Sun mass, like the Sun
   • Z, at 30 Sun masses
   • V, at 0.5 Sun mass, the smallest
   • Y, at 12 Sun masses
3. 2.

   NASA: a neutron star holds more than the Sun's mass in a city-sized ball. A white dwarf is about Earth-sized. How do they compare, by Kira's reading?

   • The neutron star is larger, since its star was bigger
   • The neutron star is much smaller and denser
   • The neutron star is a hole with nothing inside
   • They are the same size
4. 3.

   “Orbit diagram:” Imagine the Sun replaced by a black hole of the same mass. What would happen to Earth's orbit, by Luz's reading (NASA)?

   • Earth would drift off into space
   • Earth would be drawn into a tighter, faster orbit
   • Earth would be pulled in at once
   • It would stay the same; gravity there depends on mass
5. 4.

   White dwarf, neutron star, black hole. Which leftover is about Earth-sized and glows from stored heat with no fusion, by Milo's reading?

   • A red giant
   • A neutron star
   • A white dwarf
   • A black hole
6. 5.

   Why does a massive star's core collapse once it is made of iron, by Noah's reading (NASA)?

   • Iron fusion releases the most energy and blows the core apart
   • The core runs out of iron to fuse
   • Iron is too heavy to stay in the core
   • Fusing iron takes in energy instead of releasing it
7. 6.

   Helium, iron, hydrogen, silicon, carbon. In what order does a massive star's core use its fuels, by Pia's reading (NASA)?

   • Iron first, then lighter elements
   • Hydrogen, then straight to iron
   • Silicon, carbon, helium, then hydrogen
   • Hydrogen, helium, carbon, heavier ones, then silicon to iron
8. 7.

   Fusion ladder with time bars shrinking at each step. NASA: once silicon fuses into iron, the star runs out of fuel in days. Why so fast, by Ren's reading?

   • Iron fusion releases so much energy that it burns out the core
   • Silicon is the richest fuel
   • The star loses most of its mass first
   • Each new fuel gives less energy and lasts less time
9. 8.

   Three star circles labeled 0.5, 1 and 10 Sun masses. Rank stars of 0.5, 1 and 10 Sun masses from longest to shortest main-sequence life, by Tala's reading.

   • 1, then 0.5, then 10 Sun masses
   • They last equally long
   • 10, then 1, then 0.5 Sun masses
   • 0.5, then 1, then 10 Sun masses
10. 9.

    Life ≈ 10 billion years × mass^−2.5; star mass 4 Suns. A rule of thumb: main-sequence life ≈ 10 billion years × mass^−2.5 (mass in Suns). About how long does a 4-Sun-mass star last, by Zee's math?

    • About 40 billion years
    • About 320 billion years
    • About 2.5 billion years
    • About 310 million years
11. 10.

    Life ≈ 10 billion years × mass^−2.5; star life 1/100 of the Sun's. Using the same rule, a star lasts 1/100 as long as the Sun. About what is its mass, by Ari's math?

    • About 0.16 Sun mass
    • About 40 Sun masses
    • About 6 Sun masses
    • About 100 Sun masses