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 26, Problem 38Q
To determine
(a)
The Jeans length for a dark nebula assuming it to be mostly composed of hydrogen.
To determine
(b)
Whether the density fluctuations within a typical dark nebula that is several light-years away will grow with time or not.
To determine
(c)
The proof that the formation of protostar within a dark nebula is related to the growth of the nebula.
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A planetary nebula expanded in radius 0.3 arc seconds in 30 years. Doppler measurements show the nebula is expanding at a rate of 35 km/s. How far away is the nebula in parsecs?
First, determine what distance the nebular expanded in parsecs during the time mentioned. Δd = vpc/sTs
So we first need to convert the rate into pc/s and the time into seconds:
vpc/s = vkm/s (1 pc / 3.09 x 1013km)
vpc/s = ?
Ts = (Tyr)(365 days/yr)(24 hrs/day)(3600 s/hr)
Ts = ? s
Δd= vpc/sTs
Therefore, Δd = ? pc
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If we plot the apparent brightnesses of stars in a globular cluster versus their surface temperatures in a similar way as in the HR diagram , there will be a horizontal branch . Which of the following statements about these horizontal branch stars is wrong ? (A)They have the same absolute magnitude . (B)They have different sizes . (C)Their sole source of energy is hydrogen shell burning . (D)They can help us estimate the distance of the globular cluster from us .
Chapter 26 Solutions
Universe: Stars And Galaxies
Ch. 26 - Prob. 1QCh. 26 - Prob. 2QCh. 26 - Prob. 3QCh. 26 - Prob. 4QCh. 26 - Prob. 5QCh. 26 - Prob. 6QCh. 26 - Prob. 7QCh. 26 - Prob. 8QCh. 26 - Prob. 9QCh. 26 - Prob. 10Q
Ch. 26 - Prob. 11QCh. 26 - Prob. 12QCh. 26 - Prob. 13QCh. 26 - Prob. 14QCh. 26 - Prob. 15QCh. 26 - Prob. 16QCh. 26 - Prob. 17QCh. 26 - Prob. 18QCh. 26 - Prob. 19QCh. 26 - Prob. 20QCh. 26 - Prob. 21QCh. 26 - Prob. 22QCh. 26 - Prob. 23QCh. 26 - Prob. 24QCh. 26 - Prob. 25QCh. 26 - Prob. 26QCh. 26 - Prob. 27QCh. 26 - Prob. 28QCh. 26 - Prob. 29QCh. 26 - Prob. 30QCh. 26 - Prob. 31QCh. 26 - Prob. 32QCh. 26 - Prob. 33QCh. 26 - Prob. 34QCh. 26 - Prob. 35QCh. 26 - Prob. 36QCh. 26 - Prob. 37QCh. 26 - Prob. 38QCh. 26 - Prob. 39QCh. 26 - Prob. 40QCh. 26 - Prob. 41QCh. 26 - Prob. 42QCh. 26 - Prob. 43QCh. 26 - Prob. 44QCh. 26 - Prob. 45QCh. 26 - Prob. 46QCh. 26 - Prob. 47Q
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- . The radius of the nebula is about 0.401 light-years. The gas is expanding away from the star at a rate of about 37 kilometers/second . Considering that distance = velocity x time, calculate how long ago the gas left the star if its speed has been constant the whole time. Make sure you use consistent units for time, speed, and distance. Answer in years.arrow_forwardYou can estimate the age of the planetary nebula in image (c) in Figure 22.18. The diameter of the nebula is 600 times the diameter of our own solar system, or about 0.8 light-year. The gas is expanding away from the star at a rate of about 25 mi/s. Considering that distance=velocitytime , calculate how long ago the gas left the star if its speed has been constant the whole time. Make sure you use consistent units for time, speed, and distance. Figure 22.18 Gallery of Planetary Nebulae. This series of beautiful images depicting some intriguing planetary nebulae highlights the capabilities of the Hubble Space Telescope. (a) Perhaps the best known planetary nebula is the Ring Nebula (M57), located about 2000 lightyears away in the constellation of Lyra. The ring is about 1 light-year in diameter, and the central star has a temperature of about 120,000 °C. Careful study of this image has shown scientists that, instead of looking at a spherical shell around this dying star, we may be looking down the barrel of a tube or cone. The blue region shows emission from very hot helium, which is located very close to the star; the red region isolates emission from ionized nitrogen, which is radiated by the coolest gas farthest from the star; and the green region represents oxygen emission, which is produced at intermediate temperatures and is at an intermediate distance from the star. (b) This planetary nebula, M2-9, is an example of a butterfly nebula. The central star (which is part of a binary system) has ejected mass preferentially in two opposite directions. In other images, a disk, perpendicular to the two long streams of gas, can be seen around the two stars in the middle. The stellar outburst that resulted in the expulsion of matter occurred about 1200 years ago. Neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue. The planetary nebula is about 2100 light-years away in the constellation of Ophiuchus. (c) In this image of the planetary nebula NGC 6751, the blue regions mark the hottest gas, which forms a ring around the central star. The orange and red regions show the locations of cooler gas. The origin of these cool streamers is not known, but their shapes indicate that they are affected by radiation and stellar winds from the hot star at the center. The temperature of the star is about 140,000 °C. The diameter of the nebula is about 600 times larger than the diameter of our solar system. The nebula is about 6500 light-years away in the constellation of Aquila. (d) This image of the planetary nebula NGC 7027 shows several stages of mass loss. The faint blue concentric shells surrounding the central region identify the mass that was shed slowly from the surface of the star when it became a red giant. Somewhat later, the remaining outer layers were ejected but not in a spherically symmetric way. The dense clouds formed by this late ejection produce the bright inner regions. The hot central star can be seen faintly near the center of the nebulosity. NGC 7027 is about 3000 light-years away in the direction of the constellation of Cygnus. (credit a: modification of work by NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; credit b: modification of work by Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA; credit c: modification of work by NASA, The Hubble Heritage Team (STScI/AURA); credit d: modification of work by H. Bond (STScI) and NASA)arrow_forwardPictures of various planetary nebulae show a variety of shapes, but astronomers believe a majority of planetary nebulae have the same basic shape. How can this paradox be explained?arrow_forward
- From the comments in the text about which kinds of stars produce emission nebulae and which kinds are associated with reflection nebulae, what can you say about the temperatures of the stars that produce NGC 1999 (Figure 20.13)? Figure 20.13 Pleiades Star Cluster. The bluish light surrounding the stars in this image is an example of a reflection nebula. Like fog around a street lamp, a reflection nebula shines only because the dust within it scatters light from a nearby bright source. The Pleiades cluster is currently passing through an interstellar cloud that contains dust grains, which scatter the light from the hot blue stars in the cluster. The Pleiades cluster is about 400 light-years from the Sun. (credit: NASA, ESA and AURA/Caltech)arrow_forwardIf the Sun were a member of the cluster NGC 2264, would it be on the main sequence yet? Why or why not?arrow_forward
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