Match each characteristic below to the appropriate stellar end state. (Select W-White dwarf, N-Neutron star, B-Black hole. If the first is W and the rest N, enter WNNNNNNN). A) Has a mass no greater than 1.4 solar-masses. B) Sometimes appears as a pulsar. C) Size defined by its Schwarzschild radius. D) In a binary system it can explode as a supernova. E) Supported by electron degeneracy pressure. F) Typically about the size of Earth. G) Usually has a very strong magnetic field. H) Viewed from afar, time stops at its event horizon. Answer: Submit All Answers

Give ALL correct answers referring to the properties of known stars, i.e., B, AC, BCD... A) On the main sequence, more massive stars are colder. B) High mass stars are the most numerous type of stars observed in the galaxy. C) Giants are colder than main sequence stars at the same luminosity. D) Giants are brighter than dwarfs at the same temperature. E) On the main sequence, more massive stars are dimmer. F) White dwarf stars are much denser than main sequence stars. Hint: White dwarf stars have about the mass of our sun, but are only the size of the Earth. Therefore, they have a very high density.

A main sequence star of mass 25 M⊙has a luminosity of approximately 80,000 L⊙. a. At what rate DOES MASS VANISH as H is fused to He in the star’s core? Note: When we say “mass vanish '' what we really mean is “gets converted into energy and leaves the star as light”. Note: approximate answer: 3.55 E14 kg/s b. At what rate is H converted into He? To do this you need to take into account that for every kg of hydrogen burned, only 0.7% gets converted into energy while the rest turns into helium. Approximate answer = 5E16 kg/s c. Assuming that only the 10% of the star’s mass in the central regions will get hot enough for fusion, calculate the main sequence lifetime of the star. Put your answer in years, and compare it to the lifetime of the Sun. It should be much, much shorter. Approximate answer: 30 million years.

Match each characteristic below of a one-solar-mass star to its appropriate phase. Answer M for Main-sequence Star, or P for Protostar. If the first is M and the rest P, enterMPPPPPP). A) energy generated by nuclear fusion B) pressure and gravity are NOT precisely balanced. C) surface radiates energy at same rate that core generates energy D) radius much larger than the Sun E) energy generated by gravitational contraction F) lasts about 10 billion years G) luminosity much greater than the Sun