Introduction to Astronomy

Q1: sunQ2: triggerQ3: ironQ4: photodisintegrationQ5: heavy elements Q6: degenerate

Stellar Death Match II: Supernovae

Several times now, I have mentioned that stars can do two things after being Red Giants. If a star is very massive (mass greater than about 8 solar masses), they will not only evolve faster, but also manufacture heavier elements (heavier than C,N,O) during their evolution than lower mass stars do. These stars will go through a mass-losing phase, and then finally explode as supernovae.

TYPE II (CORE-COLLAPSE) SUPERNOVA SEQUENCE: For a few days, the supernova may be as bright as a whole galaxy of billions of stars! The equivalent of the entire lifetime energy budget of the Sun is released in this explosion---and that's just in light energy! As much as 100 times more energy may be carried away by neutrinos.


Crab Nebula: 1054 AD. For nearly a month, could see the supernova in the daytime!!! This is what's left "now"... It is about 1800 pc away. We can tell that the gas is moving outwards because we can measure the Doppler shift...

Vela SN Remnant: 9000 B.C. (Stone Age) As bright as the Moon for several months!!!! (only 500 pc away)

Observable SN should happen each century in our galaxy. We've not seen any in modern times. This is because of interstellar extinction due to dust in the Galaxy (recall the dust lanes across the center of the Milky Way).

Concept Question 1:
The Sun will not die by going supernova because

  1. the Sun is the Sun, and it will never die.
  2. it is too hot.
  3. it is too large.
  4. it is too massive.

Concept Question 2:
Stars go supernova when they begin to burn

  1. hydrogen.
  2. helium.
  3. carbon.
  4. iron.

Concept Question 3:
Iron sets off the supernova explosion because

  1. it is the lightest element that absorbs energy when it fuses.
  2. it's dark in color, so it absorbs the light.
  3. it's magnetic.
  4. heavier elements decay radioactively into iron.

Concept Question 4:
Photodisintegration is

  1. when light is disintegrated by running into matter.
  2. when nuclei are disintegrated by light running into them.
  3. when stars are torn apart by light.
  4. when photographs turn brown and nasty over a long period of time.

Concept Question 5:
If all the heavy elements are torn apart in the supernova explosion, where did we get all of the elements in our bodies and on the Earth?

  1. They were made in the exploding material.
  2. They come from the collisions of galaxies.
  3. They come from the collisions of stars.
  4. They formed in the Big Bang, and have been there ever since.

Concept Question 6:
Degenerate materials...

  1. Can cool without shrinking.
  2. Don't obey the ideal gas law.
  3. Are as dense as they can be without exploding.
  4. All of the above.