50%(2)1 out of 2 people found this document helpful
This preview shows page 21 - 24 out of 41 pages.
What happens to a star after the start of helium nuclear reactions in its core compared to what it was like before these reactions began?a. The star is larger and hotter.b. The star is larger and cooler.c. The star is smaller and hotter.d. The star is smaller and cooler. -c. The star is smaller and hotter.Johannes Kepler observed a supernova about 400 years ago and measurements indicate that this supernova was about 20,000 light years away from the Earth. When did the explosion actually occur?How do the stars in a star cluster change with time?
What is the last nuclear fusion stage in the life of a low-mass star like the Sun?Our Sun will end its life by becominga. a molecular cloud.b. a black hole.c. a white dwarf.d. a pulsar. -c. a white dwarf.After hydrogen burning ends in a star's core, its position on the Hertzsprung-Russell diagram moves in a direction toward theHow do astronomers know that globular clusters are very old?The escape velocity for material inside a black hole isIf you were watching a friend (or better still, an enemy!) who has fallen as far as the event horizon of a black hole, what would you measure as his heartbeat (apart from the effects caused by his adrenaline level)?
a. It would appear to have slowed down somewhat, but not much, because of the change of the speed of light in the gravity field.b. It would appear to be zero; his heart would appear to have stopped.c. It would appear to have speeded up to an incredible rate.d. It would appear to be normal since gravity has no effect on time intervals. -