How a star's mass decides its life

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   White dwarf below about 8 Suns; neutron star about 8 to 20; black hole about 20 or more (sources vary). A newly found main-sequence star is blue, with about 25 Sun masses. Which life story fits it, by Esme's reading?

   • A short life ending as a white dwarf
   • A long life of billions of years ending as a white dwarf
   • A short life, a supernova, then probably a black hole
   • A long life ending in a supernova
2. 2.

   A red main-sequence star has about 0.2 Sun mass. Which life story fits it, by Jun's reading (NASA)?

   • A few million years, then a black hole
   • It ends as a neutron star
   • A very long life with no explosion
   • A short life ending in a supernova
3. 3.

   Two stars form together: one of 3 Sun masses and one of 15. Which reaches its end first, and how, by Kira's reading?

   • The 15-Sun star, in a supernova that leaves a neutron star
   • The 15-Sun star, as a white dwarf
   • Both at the same time, as supernovas
   • The 3-Sun star, as a white dwarf after a quick, bright life
4. 4.

   Luz's friend says black holes roam space pulling in everything like vacuum cleaners. Which response is best (NASA)?

   • Disagree: black holes have no gravity
   • Agree: they pull in whole galaxies quickly
   • Disagree: from far away its gravity acts like any object of the same mass
   • Agree: nothing nearby can stay in orbit
5. 5.

   Fusion ladder from hydrogen to iron, with a stop sign at iron. Noah's friend says a massive star could keep going by fusing its iron. Which response is best (NASA)?

   • Agree: iron is the richest fuel
   • Agree: iron fusion releases the most energy of any fuel in the core
   • Disagree: massive stars stop at carbon
   • Disagree: iron fusion takes in energy, so the core collapses
6. 6.

   Drawing of an expanding shell of glowing gas. NASA studies the remnant of a supernova seen in 1572, about 13,000 light-years away. What does a supernova spread into space, by Pia's reading?

   • Nothing; its matter falls into a black hole
   • Light, but no matter
   • Pure hydrogen, just as it was after the Big Bang
   • Elements that enrich future clouds and stars
7. 7.

   In a star cluster that formed all at once, every star above 5 Sun masses has left the main sequence. What does this show, by Ren's reading?

   • Low-mass stars left first
   • Its heavy stars kept fusing iron and still shine
   • It is younger than any star's life
   • It is older than the life of a 5-Sun star
8. 8.

   Life ≈ 10 billion years × mass^−2.5; star mass 10 Suns. Using life ≈ 10 billion years × mass^−2.5, about how long does a 10-Sun-mass star last on the main sequence, by Tala's math?

   • About 1 billion years
   • About 100 billion years
   • About 300 million years
   • About 30 million years
9. 9.

   Which leftover is denser, by Zee's reading (NASA)?

   • A neutron star: more than the Sun's mass in a city-sized ball
   • They are equally dense
   • A red giant
   • A white dwarf, since it is bigger
10. 10.

    Supernova threshold 7 to 10 Sun masses; star mass 2 Suns. Sources put the supernova threshold anywhere from 7 to 10 Sun masses. Which statement about a 2-Sun-mass star holds for every source, by Bo's reading?

    • It becomes a black hole
    • It ends in a supernova
    • It becomes a neutron star
    • It ends as a white dwarf