Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 21, Problem 4E
Describe what happens when a star forms. Begin with a dense core of material in a molecular cloud and trace the evolution up to the time the newly formed star reaches the main sequence.
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Which 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.
Select all of the statements about the main sequence stage in the life of a star that are TRUE:
All stars spend the majority of their lives in the main sequence stage.
Most stars lose a significant amount of mass while they are on the Main Sequence.
Different stars spend a different amounts of time (number of years) in the main sequence stage, depending on the characteristics they were born with.
Main sequence stars are rare in the Galaxy, so we are lucky to be living around one.
During the main sequence stage, energy to power the star is provided by the fusion of hydrogen.
For 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.
Chapter 21 Solutions
Astronomy
Ch. 21 - Give several reasons the Orion molecular cloud is...Ch. 21 - Why is star formation more likely to occur in cold...Ch. 21 - Why have we learned a lot about star formation...Ch. 21 - Describe what happens when a star forms. Begin...Ch. 21 - Describe how the T Tauri star stage in the life of...Ch. 21 - Look at the four stages shown in Figure 21.8. In...Ch. 21 - The evolutionary track for a star of 1 solar mass...Ch. 21 - Two protostars, one 10 times the mass of the Sun...Ch. 21 - Compare the scale (size) of a typical dusty disk...Ch. 21 - Why is it so hard to see planets around other...
Ch. 21 - Why did it take astronomers until 1995 to discover...Ch. 21 - Which types of planets are most easily detected by...Ch. 21 - List three ways in which the exoplanets we have...Ch. 21 - List any similarities between discovered...Ch. 21 - What revisions to the theory of planet formation...Ch. 21 - Why are young Jupiters easier to see with direct...Ch. 21 - A friend of yours who did not do well in her...Ch. 21 - Observations suggest that it takes more than 3...Ch. 21 - Suppose you wanted to observe a planet around...Ch. 21 - Why were giant planets close to their stars the...Ch. 21 - Exoplanets in eccentric orbits experience large...Ch. 21 - When astronomers found the first giant planets...Ch. 21 - An exoplanetary system has two known planets....Ch. 21 - Kepler’s third law says that the orbital period...Ch. 21 - Calculate the transit depth for an M dwarf star...Ch. 21 - If a transit depth of 0.00001 can be detected with...Ch. 21 - What fraction of gas giant planets seems to have...
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- Describe the evolution of a star with a mass similar to that of the Sun, from the protostar stage to the time it first becomes a red giant. Give the description in words and then sketch the evolution on an HR diagram.arrow_forwardLook at the four stages shown in Figure 21.8. In which stage(s) can we see the star in visible light? In infrared radiation? Figure 21.8 Formation of a Star. (a) Dense cores form within a molecular cloud. (b) A protostar with a surrounding disk of material forms at the center of a dense core, accumulating additional material from the molecular cloud through gravitational attraction. (c) A stellar wind breaks out but is confined by the disk to flow out along the two poles of the star. (d) Eventually, this wind sweeps away the cloud material and halts the accumulation of additional material, and a newly formed star, surrounded by a disk, becomes observable. These sketches are not drawn to the same scale. The diameter of a typical envelope that is supplying gas to the newly forming star is about 5000 AU. The typical diameter of the disk is about 100 AU or slightly larger than the diameter of the orbit of Pluto.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_forward
- Based on what you know about main-sequence stars, select all of the correct statements from the following list. 1. Since the interiors of stars cannot be observed, there are no theories about their structure. 2. More massive stars are hotter and brighter. 3. The weight of a star must be balanced by internal pressure. 4. More massive stars live longer; they take longer to use up all their energy. 5. Stars change position on the main sequence throughout their lives. 6. Outward energy flow in a star is by conduction only.arrow_forwardBased on what you learned about stellar structure and how stars maintain their stability, select all of the correct statements from the following list. 1. The weight pressing down on a layer of gas in a star is balanced by the pressure in the gas. 2. The interior of the lowest-mass stars transfers energy mostly through convection. 3. Energy in a star flows from the core to the surface. 4. More massive stars produce energy with the proton-proton cycle. 5. Less massive stars produce energy with the CNO cycle. 6. Conduction is an important method of energy transport in stars. 7. Stars are hotter in their cores than on their surfaces.arrow_forwardYou discover a binary star system in which one member is a 15 solar-mass main-sequence star and the other star is a 10 solar-mass giant. Why should you be surprised, at least at first? A. It doesn't make sense to find a giant in a binary star system. B. The two stars in a binary system should both be at the same point in stellar evolution; that is, they should either both be main-sequence stars or both be giants. C. The two stars should be the same age, so the more massive one should have become a giant first. D. The odds of ever finding two such massive stars in the same binary system are so small as to make it inconceivable that such a system could be discovered. E. A star with a mass of 15 solar-mass is too big to be a main-sequence star.arrow_forward
- The chemical abundance of population I stars a. indicates that they were formed before the population II stars. b. indicates that the material they formed from had been enriched with material from supernovae. c. indicates that they contain very few heavy metals compared to halo stars. d. depends on the temperature of the star. e. depends on the mass of the star.arrow_forwardWhich 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.arrow_forwardHow high or low a star is on the main sequence is dictated primarily by ... Select one: A. its chemical composition B. the fraction of metals in its atmosphere C. what elements are fusing in its core D. the size of its photosphere E. its massarrow_forward
- Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high- mass star is not true? A. As each stage ends, the core shrinks and heats further. B. Each successive stage creates an element with a higher atomic number and atomic mass number. C. As each stage ends, the reactions that occurred in previous stages continue in shells around the core. D.Each successive stage lasts for approximately the same amount of time.arrow_forwardOutline the process of star formation, including all relevant factors that influence the outcome.arrow_forwardAs a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first? 1) all the stars in a cluster are born at the same time; so they will all move off the main sequence at the same time, as they evolve 2) G type stars, like our Sun 3) M type stars, which are the coolest 4) the lowest mass stars, which have the least amount of fuel for fusion 5) the O and B type starsarrow_forward
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