2. Circle the answer that you think is correct. a) Could a star that had 30 time
ID: 294352 • Letter: 2
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2. Circle the answer that you think is correct. a) Could a star that had 30 times the mass of the Sun when it was on the Main Sequence end up as a i) White Dwarf? ii) Neutron Star? iii) Black Hole? b) Could a star with a core two times the mass of the Sun end up as a: i) White Dwarf? ii) Neutron Star? iii) Black Hole? c) A star had 10 times the mass of the Sun when it was on the Main Sequence. At the end of its life it has a core with a mass 1.5 times the mass of the Sun. Explain what happened to the rest of the mass and why. 3. Which effect has been successful in the search for and identification of black holes in the universe? a) their magnetic fields and their influence on nearby matter. b) the effect of their angular momentum or spin on nearby matter. c) the light emitted from the event horizons of the black holes. their gravitational influence on nearby matter, particularly companion stars. 4. What would happen to the gravitational force on the Earth if the Sun were magically replaced by a 1 solar- mass black hole? a) It would double in strength. b) It would be much less, because the gravitational field of a black hole exists only very close to it. d) It would become extremely high, sufficient to pull the Earth into it 5. The most probable theory for the solar system's formation is a) the gravity of the Sun captured objects moving through space which then became the planets b) gas and dust clouds condensed to form the Sun and a protoplanetary disk in which the planets formed c) condensation of a slowly contracting nebula of hot gas, first into planets in the outer solar system and later into the Sun at the center d) an encounter in which a passing star ripped material off the Sun to form planets e) the heavy elements in the center of a supernova explosion condensed to form the Sun and planetsExplanation / Answer
Correct answer 2 a. Black hole 2. b. Neutron star 2.c. The relationship between brightness and mass has serious implications for the lifetimes of the Main Sequence stars. The fuel that keeps stars shining is their mass and stars that have more mass have more fuel to burn, so you might expect them to last longer than stars with less mass. But the rate at which the fuel has to be burnt is proportional to luminosity, so brighter stars shouldn't last as long as fainter ones. The ratio of a star's lifetime to the lifetime of the Sun would be given by how much more fuel it has, divided by how much faster it is burning that fuel. Since for most of the range of stellar masses Main Sequence stars which are twice as bright are burning their fuel ten times faster , their fuel will only last about one-fifth as long. As a result, we can modify the table shown above to include the lifetimes of the stars. 3. The light emiited from the event horizon of the black holes 4. It would double in strength 5. The gas and dustv cloud condensed to form sun and protoplanetary disc in which the planets was formed.
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