How a star's mass decides its life
Grade 9 Science Worksheet
Circle the best answer.
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).
Which star in the table will end as a neutron star, by Bo's reading?
- Z, at 30 Sun masses
- Y, at 12 Sun masses
- W, at 1 Sun mass
- X, at 5 Sun masses
Which is the heaviest star in the table that will end as a white dwarf, by Esme's reading?
- X, at 5 Sun masses
- Y, at 12 Sun masses
- Z, at 30 Sun masses
- No star here; each one explodes
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
- Y, at 12 Sun masses
- V, at 0.5 Sun mass, the smallest
- Z, at 30 Sun masses
“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 be drawn into a tighter, faster orbit
- Earth would be pulled in at once
- It would stay the same; gravity there depends on mass
- Earth would drift off into space
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
- Iron is too heavy to stay in the core
- The core runs out of iron to fuse
- Fusing iron takes in energy instead of releasing it
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
- Silicon, carbon, helium, then hydrogen
- Hydrogen, helium, carbon, heavier ones, then silicon to iron
- Hydrogen, then straight to iron
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?
- Silicon is the richest fuel
- Each new fuel gives less energy and lasts less time
- Iron fusion releases so much energy that it burns out the core
- The star loses most of its mass first
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.
- 10, then 1, then 0.5 Sun masses
- 1, then 0.5, then 10 Sun masses
- 0.5, then 1, then 10 Sun masses
- They last equally long
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 310 million years
- About 2.5 billion years
- About 40 billion years
- About 320 billion years
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 40 Sun masses
- About 0.16 Sun mass
- About 6 Sun masses
- About 100 Sun masses