21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 15, Problem 14QP
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3. Brown dwarfs are ____. a. stars with a very thick dust sphere around them, so they appear “brown” b. low mass M type stars with hundreds of planets c. an anomaly because they are extremely small but have relatively high temperature d. protostars that could not ignite the fusion of hydrogen at their core e. has a surface temperature of 2500 K by fusing hydrogen
I asked this question onece already, but the answer I got said the answer was C because "AT 2700K THEY ARE HOT" or something to that effect. I tried to find a way to reply to that thread. My argument was that even if brown dwarfs were 2700k (and my book says that's closer to the temperature of red dwarfs and that brown dwarfs are usually around 1000K). Seeing that we are studying the life cycle and evolution of all stars, wouldn't either of those temperatures be on the relatively COOL side of all star temperatures? Wouldn't the most appropriate answer be D.?
As a white dwarf cools, its radius will not change because
a.
pressure resulting from nuclear reactions in a shell just below the surface keeps it from collapsing.
b.
pressure does not depend on temperature for a white dwarf because the electrons are degenerate.
c.
pressure does not depend on temperature because the white dwarf is too hot.
d.
pressure does not depend on temperature because the star has exhausted all its nuclear fuels.
e.
material accreting onto it from a companion maintains a constant radius.
Which of the following binary star systems cannot exist?
A. A 1 solar-mass main sequence star and a 4 solar mass red giant with a size 100 times smaller than the orbital distance.
B. A 15 solar-mass main sequence star and a 10 solar mass red giant with a size 100 times smaller than the orbital distance.
C. A 1 solar-mass main sequence star and a 4 solar-mass main sequence star.
D. A 2 solar-mass main sequence star and a 1 solar mass red giant with a size a few times smaller than the orbital distance.
Chapter 15 Solutions
21st Century Astronomy
Ch. 15.1 - Prob. 15.1CYUCh. 15.2 - Prob. 15.2CYUCh. 15.3 - Prob. 15.3CYUCh. 15.4 - Prob. 15.4CYUCh. 15 - Prob. 1QPCh. 15 - Prob. 2QPCh. 15 - Prob. 3QPCh. 15 - Prob. 4QPCh. 15 - Prob. 5QPCh. 15 - Prob. 6QP
Ch. 15 - Prob. 7QPCh. 15 - Prob. 8QPCh. 15 - Prob. 9QPCh. 15 - Prob. 10QPCh. 15 - Prob. 11QPCh. 15 - Prob. 12QPCh. 15 - Prob. 13QPCh. 15 - Prob. 14QPCh. 15 - Prob. 15QPCh. 15 - Prob. 16QPCh. 15 - Prob. 17QPCh. 15 - Prob. 18QPCh. 15 - Prob. 19QPCh. 15 - Prob. 20QPCh. 15 - Prob. 21QPCh. 15 - Prob. 22QPCh. 15 - Prob. 23QPCh. 15 - Prob. 24QPCh. 15 - Prob. 25QPCh. 15 - Prob. 26QPCh. 15 - Prob. 27QPCh. 15 - Prob. 28QPCh. 15 - Prob. 29QPCh. 15 - Prob. 30QPCh. 15 - Prob. 31QPCh. 15 - Prob. 32QPCh. 15 - Prob. 33QPCh. 15 - Prob. 35QPCh. 15 - Prob. 36QPCh. 15 - Prob. 37QPCh. 15 - Prob. 38QPCh. 15 - Prob. 39QPCh. 15 - Prob. 40QPCh. 15 - Prob. 41QPCh. 15 - Prob. 42QPCh. 15 - Prob. 43QPCh. 15 - Prob. 44QPCh. 15 - Prob. 45QP
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- There is a mass–luminosity relation because a. hydrogen fusion produces helium. b. stars expand when they become giants. c. stars support their weight by making energy. d. the helium flash occurs in degenerate matter. e. all stars on the main sequence have about the same radius.arrow_forwardThe triple-alpha process a. controls the pulsations in Cepheid variable stars. b. is the nuclear fusion of hydrogen to helium in massive stars. c. is the process that produces the neutrinos we receive from the sun. d. requires a temperature of about 5,000,000 K to operate. e. fuses helium nuclei to make carbon and occurs during helium flash.arrow_forwardThe theory that the collapse of a massive star’s iron core produces neutrinos was supported by a. the size and structure of the Crab nebula. b. laboratory measurements of the mass of the neutrino. c. the brightening of supernovae a few days after they are first visible. d. underground counts from solar neutrinos. e. the detection of neutrinos from the supernova of 1987.arrow_forward
- The gas and dust cocoon surrounding young stars a. is blown away when the young stellar surface heats up and becomes more luminous. b. remains surrounding the young star throughout its adult life. c. eventually collapses onto the star, increasing its mass and luminosity. d. evaporates gradually over the lifetime of the star. e. expands as the star’s luminosity increases eventually reaching a distance far enough that it condenses to form comets.arrow_forwardWhich of the following is wrong? A. Tidal effects in a binary star system become more important when one or both stars become giant stars. B. There is no fusion occurring in the core of a low-mass red giant star. C. Gold (the element) is produced during the supernova explosions of high-mass stars. D. Suppose the star Betelgeuse were to become a supernova tomorrow, we'd see by naked eyes a cloud of gas expanding away from the position where Betelgeuse used to be. Over a period of a few weeks, this cloud would fill a large part of our sky.arrow_forwardWhy are we unlikely to find Earth-like planets around halo stars in the Galaxy? A. Halo stars formed in a different way from disk stars. B. Planets around stars are known to be extremely rare. C. Halo stars formed in an environment where there were few heavy elements to create rocky planets. D. Halo stars do not have enough mass to hold onto planets. Is the answer C? Since halo stars are formed early when the galaxy consisted of mainly hydrogen and helium, there are no heavier elements available to create Earth-like planets so just halo stars are formed? Thanks!arrow_forward
- The place on the H–R diagram where contracting protostars first become visible is a. the horizontal branch. b. the instability strip. c. the birth line. d. the zero-age main sequence. e. none of the above.arrow_forwardWhere does gold (the element) come from? A. It is produced during the supernova explosions of high-mass stars. B. It was produced during the Big Bang. C. It is produced by mass transfer in close binaries. D. It is produced during the late stages of fusion in low-mass stars.arrow_forwardWhich of the following statements is wrong? A. A main-sequence star is cooler and brighter than it was as a protostar. B. Carbon fusion occurs in high-mass stars but not in low-mass stars because the cores of low-mass stars never contain significant amounts of carbon. C. when a main-sequence star exhausts its core hydrogen fuel supply, the core shrinks while the rest of the star expands. D. After a supernova explosion, the remains of the stellar core will be either a neutron star or a black hole.arrow_forward
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