Choose the correct statements from the following list referring to white dwarfs. (Give ALL correct answers, i.e. B, AB, BCD...) A) Stars with a mass like the Sun will end up as a white dwarf star. B) White dwarfs with mass greater than 1.4 times the Sun's mass cannot exist. C) White dwarfs are less dense than red giants. D) The pressure that balances gravity in a white dwarf is called degenerate electron pressure. E) White dwarfs cool slowly because they are small and eventually fade-out to become black dwarfs. F) The power source of white dwarfs is left-over heat. G) White dwarfs are the coolest main sequence stars.

Choose the correct statements from the following list referring to white dwarfs. (Give ALL correct answers, i.e. B, AB, BCD...) A) Stars with a mass like the Sun will end up as a white dwarf star. B) White dwarfs with mass greater than 1.4 times the Sun's mass cannot exist. C) White dwarfs are less dense than red giants. D) The pressure that balances gravity in a white dwarf is called degenerate electron pressure. E) White dwarfs cool slowly because they are small and eventually fade-out to become black dwarfs. F) The power source of white dwarfs is left-over heat. G) White dwarfs are the coolest main sequence stars.

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Suppose two protostars form at the same time, one with a mass of 0.5MSunSun [Select ALL answers that are true in alphabetical order]A) The 10MSun protostar will have a smaller change in surface temperature during this phase than the 0.5MSun protostar.B) The 10MSun protostar will reach the main sequence cooler and fainter than the 0.5MSun protostar.C) The 10MSun star will end its main-sequence life before the 0.5MSun star even completes its protostar stage.D) The 10MSun protostar will have a smaller change in luminosity during the sequence shown than the 0.5MSun protostar.E) The 10MSun protostar will be much more luminous than the 0.5MSun protostar.
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
Suppose a protostar has a luminosity of 39,473 L⊙ and a surface temperature of 4,130 K (Kelvins). What is the radius of this protostar? [Enter your answer as a multiple of the Sun's radius. I.e., if you find R = 20 R⊙ , enter 20. This problem is easier if you start with the relevant equation and create a ratio using the Sun's values. Recall that the Sun has a surface temperature of 5778 K. ]
Identify the location in the H-R diagram of the phases of stellar evolution. (For each statement select the proper symbol in the picture.) 1) red giant, helium flash2) white dwarf3) red giant with helium burning shell4) hydrogen fusion in shell around core5) helium fusion in core6) envelope ejected, planetary nebula7) main-sequence star8) helium used up, core collapses9) hydrogen used up, core collapses
Which of the following most correctly explains why we have not yet observed any white dwarfs derived from M stars: Group of answer choices Most M stars end up as neutron stars or black holes. The lifetime of M stars is longer than the age of the universe. Most M stars are located near the edge of the universe, beyond the visible horizon. Most M stars are members of a binary system, and the white dwarf would be obscured by the glare of the more massive companion. White dwarfs are too dim to be observed with currently available techniques.
A star is listed in a catalog as being a type G2V.a) What is the star’s spectral class?b) What is the star’s luminosity class?c) What is the peak color of the star?d) Name an example of a star that has this type.
A star with spectral type A0 has a surface temperature of 9600 K and a radius of 2.2 RSun. How many times more luminous is this star than the Sun? (if it is less luminous enter a number less than one) 36.854 This star has a mass of 3.3 MSun. Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr.
(Answer don't copy with hand written please)As a star runs out of hydrogen to fuel nuclear fusion in its core, changes within the star usually cause it to leave the main sequence, expanding and cooling as it does so. Would a star with a radius 12 times that of the Sun, but a surface temperature 0.5 times that of the Sun, be more, or less luminous than the Sun? Show and explain your reasoning. You may assume the surface area of a sphere is A = 4πr2.