Understanding Our Universe
3rd Edition
ISBN: 9780393614428
Author: PALEN, Stacy, Kay, Laura, Blumenthal, George (george Ray)
Publisher: W.w. Norton & Company,
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Chapter 12, Problem 15QAP
To determine
The main-sequence turnoff of cluster at
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A protostar will continue to collapse due to gravity until it reaches the main
sequence, and then gravitational collapse will stop when a. the formation of star-globularsb. atoms degenerate at the core of the starc. the fusion of hydrogen
d. the fusion of heliume. the fission of hydrogen
A protostar evolves from a temperature T = 3500 K and a luminosity L = 5000 times that of the Sun to T = 5000 K and L = 3 solar units. What is its radius (a) at the start, and (b) at the end of the evolution? [Hint: Week 6 slide 13]
Place 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
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Chapter 12 Solutions
Understanding Our Universe
Ch. 12.1 - Prob. 12.1CYUCh. 12.2 - Prob. 12.2CYUCh. 12.3 - Prob. 12.3CYUCh. 12.4 - Prob. 12.4CYUCh. 12.5 - Prob. 12.5CYUCh. 12.6 - Prob. 12.6CYUCh. 12 - Prob. 1QAPCh. 12 - Prob. 2QAPCh. 12 - Prob. 3QAPCh. 12 - Prob. 4QAP
Ch. 12 - Prob. 5QAPCh. 12 - Prob. 6QAPCh. 12 - Prob. 7QAPCh. 12 - Prob. 8QAPCh. 12 - Prob. 9QAPCh. 12 - Prob. 10QAPCh. 12 - Prob. 11QAPCh. 12 - Prob. 12QAPCh. 12 - Prob. 13QAPCh. 12 - Prob. 14QAPCh. 12 - Prob. 15QAPCh. 12 - Prob. 16QAPCh. 12 - Prob. 17QAPCh. 12 - Prob. 18QAPCh. 12 - Prob. 19QAPCh. 12 - Prob. 20QAPCh. 12 - Prob. 21QAPCh. 12 - Prob. 22QAPCh. 12 - Prob. 23QAPCh. 12 - Prob. 24QAPCh. 12 - Prob. 25QAPCh. 12 - Prob. 26QAPCh. 12 - Prob. 27QAPCh. 12 - Prob. 28QAPCh. 12 - Prob. 29QAPCh. 12 - Prob. 30QAPCh. 12 - Prob. 32QAPCh. 12 - Prob. 33QAPCh. 12 - Prob. 34QAPCh. 12 - Prob. 35QAPCh. 12 - Prob. 36QAPCh. 12 - Prob. 37QAPCh. 12 - Prob. 38QAPCh. 12 - Prob. 39QAPCh. 12 - Prob. 40QAPCh. 12 - Prob. 42QAPCh. 12 - Prob. 43QAPCh. 12 - Prob. 44QAPCh. 12 - Prob. 45QAP
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- 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_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_forwardYou can use the equation in Exercise 22.34 to estimate the approximate ages of the clusters in Figure 22.10, Figure 22.12, and Figure 22.13. Use the information in the figures to determine the luminosity of the most massive star still on the main sequence. Now use the data in Table 18.3 to estimate the mass of this star. Then calculate the age of the cluster. This method is similar to the procedure used by astronomers to obtain the ages of clusters, except that they use actual data and model calculations rather than simply making estimates from a drawing. How do your ages compare with the ages in the text? Figure 22.10 NGC 2264 HR Diagram. Compare this HR diagram to that in Figure 22.8; although the points scatter a bit more here, the theoretical and observational diagrams are remarkably, and satisfyingly, similar. Figure 22.12 Cluster M41. (a) Cluster M41 is older than NGC 2264 (see Figure 22.10) and contains several red giants. Some of its more massive stars are no longer close to the zero-age main sequence (red line). (b) This ground-based photograph shows the open cluster M41. Note that it contains several orange-color stars. These are stars that have exhausted hydrogen in their centers, and have swelled up to become red giants. (credit b: modification of work by NOAO/AURA/NSF) Figure 22.13 HR Diagram for an Older Cluster. We see the HR diagram for a hypothetical older cluster at an age of 4.24 billion years. Note that most of the stars on the upper part of the main sequence have turned off toward the red-giant region. And the most massive stars in the cluster have already died and are no longer on the diagram. Characteristics of Main-Sequence Starsarrow_forward
- According to the text, a star must be hotter than about 25,000 K to produce an H II region. Both the hottest white dwarfs and main-sequence O stars have temperatures hotter than 25,000 K. Which type of star can ionize more hydrogen? Why?arrow_forwardIn 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_forward
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