Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 18, Problem 48Q
To determine
To explain:
The effect on the internal structure of main sequence stars if electrons in hydrogen atoms were not as strongly attracted to the nuclei of those atoms and so, the atoms were easier to ionize.
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For a main sequence star with luminosity L, how many kilograms of hydrogen is being converted into helium per second? Use the formula that you derive to estimate the mass of hydrogen atoms that are converted into helium in the interior of the sun (LSun = 3.9 x 1026 W).
(Note: the mass of a hydrogen atom is 1 mproton and the mass of a helium atom is 3.97 mproton. You need four hydrogen nuclei to form one helium nucleus.)
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)
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.
Compare this to the lifetime of a A0 star listed in Table 22.1 (computed using a more sophisticated approach). Is the value you calculated in the previous problem longer or shorter than what is reported in the table? (L for longer, S for shorter) (You only get one try at this problem.)
All massive main sequence stars reside in clouds of glowing gas. The four powerful stars in the center of the Orion Nebula are good examples. Lower mass stars like the Sun generally don't have clouds of gas around them. a. Why do powerful stars reside in gas clouds? b. What is making the gas glow exactly? For the last question, refer to the surface temperature of these stars, and to Wien's Law.
Chapter 18 Solutions
Universe: Stars And Galaxies
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- In the HR diagrams for some young clusters, stars of both very low and very high luminosity are off to the right of the main sequence, whereas those of intermediate luminosity are on the main sequence. Can you offer an explanation for that? Sketch an HR diagram for such a cluster.arrow_forwardPlace the following events in the formation of stars in the proper chronological sequence, with the oldest first and the youngest last. w. the gas and dust in the nebula flatten to a disk shape due to gravity and a steadily increasing rate of angular rotation x. a star emerges when the mass is great enough and the temperature is high enough to trigger thermonuclear fusion in the core y. the rotation of the nebular cloud increases as gas and dust concentrates by gravity within the growing protostar in the center z. some force, perhaps from a nearby supernova, imparts a rotation to a nebular cloud y, then z, then w, then x z, then y, then w, then x w, then y, then z, then x z, then x, then w, then y x, then z, then y, then w MacBook Air on .H. O O O Oarrow_forwardGive 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.arrow_forward
- What are the three possible outcomes of stellar evolution? Describe each possibility, differentiating their means of formation and their subsequent properties. Which stars on the Main Sequence are thought to end up in each of these forms?arrow_forwardThe figure above shows a track on the H-R diagram corresponding to the evolution of a star like the one you’ve just considered. Six stages are numbered. Six stages of stellar evolution are listed below – for each stage, write the number corresponding to its position on the diagram (four of these stages are the same stages you considered in the first part of this tutorial). Horizontal branch: Asymptotic giant branch: White dwarf: Main sequence: Planetary nebula: Red giant branch: What is the approximate mass of this star, in solar masses? Explain how you can tell.arrow_forwardHow are giant molecular clouds (GMCs), the loci of most star formation, themselves formed out of diffuse interstellar gas? What processes determine the distribution of physical conditions within star-forming regions, and why does star formation occur in only a small fraction of the available gas? How is the rate at which stars form determined by the properties of the natal GMC or, on a larger scale, of the interstellar medium (ISM) in a galaxy? What determines the mass distribution of forming stars, the initial mass function (IMF)? Most stars form in clusters (Lada & Lada 2003); how do stars form in such a dense environment and in the presence of enormous radiative and mechanical feedback from other YSOs?arrow_forward
- The mass-luminosity relation describes the mathematical relationship between luminosity and mass for main sequence stars. It describes how a star with a mass of 4 M⊙ would have a luminosity of ______ L⊙. If a star has a radius 1/2 that of the Sun and a temperature 4 that of the Sun, how many times higher is the star's luminosity than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a radius 2 times larger than the Sun's and a luminosity 1/4th that of the Sun, how many times higher is the star's temperature than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125) If a star has a surface temperature 2 times lower than the Sun's and a luminosity the same as the Sun, how many times larger is the star than the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125)arrow_forwardQuestion 41 .Suppose you are looking at H-R diagrams of two similar star clusters. The most luminous main sequence stars in the Porcini cluster are much more luminous than the most luminous main sequence stars in the Morel cluster. What can you conclude? O the Porcini cluster is younger than the Morel cluster O the Porcini cluster is farther away than the Morel cluster O the Porcini cluster is lower in metallicity than the Morel cluster O the Porcini cluster is larger in diameter than the Morel clusterarrow_forwardFor each statement concerning main sequence stars, select T True, F False, G Greater than, L Less than, or E Equal to. A) The surface temperature of a O type star is .... than a K type star. B) On the main sequence, the mass of a O type star is .... than a F type star. C) On the main sequence, a M type star's life is .... than a G type star. D) The surface temperature of our Sun is .... than the surface temperature of Sirius. E) When stars start hydrogen burning, thier mass determines where they are on the main sequence. F) Based on the relative lifes of M and G type stars we expect the number of M stars to be .... than the number of G type stars.arrow_forward
- If the hottest star in the Carina Nebula has a surface temperature of 51,000 K, at what wavelength (in nm) does it radiate the most energy? Hint: Use Wien's law: ?max = 2.90 ✕ 106 nm · K T How does that compare with 91.2 nm, the wavelength of photons with just enough energy to ionize hydrogen? -The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen. -The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen. -The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen. -The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.arrow_forwardFinally estimate the lifetime of an M0 spectral type star if the total mass of the star is M = 0.51M⊙ , and it has a total luminosity L = 7.7× 10−2L⊙. Make the same assumptions as the previous two problems. How does your calculated Main Sequence lifetime for the M0 type star compare to the Main Sequence lifetime you calculated for the Sun?arrow_forwardChoose the correct statements concerning spectral classes of stars. (Give ALL correct answers, i.e., B, AC, BCD...) A) Neutral hydrogen lines dominate the spectrum for stars with temperatures around 10,000 K because a lot of the hydrogen is in the n=2 level. B) Hydrogen lines are weak in type O-stars because most of it is completely ionized. C) Oh Be A Fine Guy/Girl Kiss Me, is a mnemonic for remembering spectral classes. D) The spectral sequence has recently been expanded to include L, T, and Y classes. E) K-stars are dominated by lines from ionized helium because they are so hot. F) The spectral types of stars arise primarily as a result of differences in temperature.arrow_forward
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