1. The Effects of Gravity

2. Identify the source of gravitational forces and fields Identify the source of gravitational forces and fields. Identify the strongest gravitational force that you personally experience. Use your mass to calculate the gravitational force that you experience each day. F g = m x 10N / 1 kg Gravitational fields can be represented by arrows pointing down towards the center of a mass. Sketch the gravitational fields that exist between you and the earth.

3. Gravity on a Star Explain what should happen if the star produces massive amounts of energy. Explain what would happen if the star produces a smaller amount of energy. A star has an enormous mass. This causes it to also have an enormous F g. Identify what happens when you exert a force over an area. The pressure from the star’s F g causes the particles in the star to compress and undergo nuclear fusion. The energy from this fusion is released as light and also balances the inward pressure from the star’s F g.

4. Gravity on a Star A “young” star fuses hydrogen into deuterium and deuterium into helium. These stars appear yellow, like our sun. A star with a helium core can begin to fuse helium into carbon. These stars are white dwarf stars. They balance the F g by having e - repel each other. As a star runs out of hydrogen it can become a red or orange giant, such as Betelgeuse or Arcturus. Our sun will end at this point. Explain what should happen to a star with a larger mass than our sun.

5. Comparing Stars Describe the differences in size you see between the sun and other stars.

6. Gravity on Larger Stars Identify the colors you expect to see from an iron core star or a neutron star. Explain how you would demonstrate that radio waves were emitted by a star. A more massive star has a greater F g, so the star continues to collapse, fusing carbon into iron, then crushing electrons into protons to create neutrons. These neutron stars are also called “pulsars” because they release light energy as radio waves, sending “mysterious” signals.

7. Gravity on the Largest Stars Determine the circumference you would have to compress to in order to become a black hole. Our sun would become a black hole if its circumference becomes 18 km. Determine its mass. If a star has even more mass, the magnitude of its F g is so large that it continues to collapse from a neutron star and either tears itself apart in a supernova or completes its gravitational collapse into a black hole. The equation to determine if a star is large enough to become a black hole is Kip Thorne’s Hoop Conjecture: C = 2π x mass x (1.48 x 10 -27 m/kg)

8. Gravity on the Largest Stars Black holes are “black” and do not shine like stars. Suggest how scientists might be able to identify black holes in the universe. Describe some of the phenomena that take place around a black hole. These can be ideas you have heard about, seen, or read about. Explain why it might be difficult to make careful observation of black holes. Explain what you think ultimately happens to black holes.