Corrections for Astronomy Today, 3rd ed.

Chaisson and McMillan

                            by Donald Gudehus

Page 10, 1st column, line 7

    The actual relative brightnesses of Betelgeuse and Rigel depend both on time (since Betelgeuse is a variable star) and wavelength. Betelgeuse is an M2 supergiant with a color of B-V=1.85, and Rigel is a B8 supergiant with a color of B-V=-0.03. Therefore, given that the current magnitudes of Betelgeuse and Rigel are V=0.44 and V=0.12, making Betelgeuse slightly dimmer than Rigel, a slight shift of the wavelength band redward of V would make Betelgeuse quite a bit brighter than Rigel. In this course we will consider Betelgeuse as being the brighter of the two stars.
Pages 103 to 104, section on Light-Gathering Power
    The discussion applies only to a point source object, or to an unresolved source. For real objects, the diameter of the image must be taken into account. Since longer focal length telescopes produce larger images, the surface brightness of an image depends of the square of the ratio of telescope diameter to focal length, or inversely on the square of the focal ratio. It is true however that the total amount of light in the image depends on the square of the telescope diameter.
Page 148, 1st column, section on Earth's density
Page 193, 2nd column, section on Mercury's density
    Notice that the earth's density is given as 5.5 g cm-3 and Mercury's is given as 5.43 g cm-3, 0.98 that of Earth, yet Figure 8.25 shows that Mercury's core is proportionally bigger. Any comparison of terrestrial planets' density must only be done on the uncompressed density. Since Earth's uncompressed density is 4.2 g cm-3, Figure 8.25 does actually make sense. Disregard the factor of 0.98 for density comparison.
Page 195, Figure 8.24
    This figure tries to combine information on density (crust, mantle, and core) with information on rigidity (lithosphere and asthenosphere) in the Moon. The figure is not truly successful in this endeavor however; two separate figures would have been a better choice. Recall that the thickness of the crust is 60 (nearside) to 100 (farside) km, the thickness of the mantle 1200 km, and the radius of the core, 400 to 500 km. The thickness of the lithosphere is 1000 km, and the asthenosphere is the outer 500 km of the inner 700 km radius sphere.
Page 209, Figure 9.A
    At latitude=63, longitude=336, change "Secojawea" to Sacajawea".
Page 218, 1st column, line 7 from bottom
    Change "half" to "70 percent".
Page 227, Interlude 10-1
    The first person to use the term canali for Mars was the Italian astronomer Angelo Secchi in 1869.
Page 292, 2nd column, line 10
    The statement about the temperature at which ammonia freezes into ice crystals is in conflict with Figure 11.6 (page 248) which shows the temperature of the ammonia ice clouds in Jupiter's atmosphere. The temperature given on page 292 is wrong; the temperature is closer to 125 K. Methane however freezes at a temperature of about 70 K. Also delete the sentence following this one. Ammonia is not seen in the atmosphere of Uranus and Neptune because it forms clouds deeper down (below the methane clouds) and is obscured. On Jupiter, ammonia forms clouds high in the atmpshere (above all the other clouds) and is readily observed in its gaseous state.
Page 294, Figure 13.9
    The magnetic polarity of every planet is just the opposite of what is indicated. That is, each instance of "N" should be replaced by "S".
Page 363, 1st column, line 10
    Change "above the" to "above the base of the".
Page 363, Caption for Figure 16.13
    Change "outer edge" to "inner edge".
Page 363, Figure 16.13
    Change the X axis label from "Distance above photosphere (km)" to "Distance above base of photosphere (km)". Shift the pink section marked Chromosphere to run from 500 km to about 7000 km. The photosphere runs from 0 to 500 km, and spicules in the chromosphere can reach to 7000 km.
Page 388, Figure 17.11
    The temperatures given in the figure are not consistent with the positions of the peaks of the curves. The actual temperatures are close to 19,500 K, 4,420 K, and 2500 K. The figure attempts to show that for a 10,000 K star, the B and V intensities are equal. However they are not equal; it is the B and V magnitudes that are equal and only because of a hidden scaling factor that cannot be shown in the figure. Ignore this figure.
Page 434, 1st column, line 15 from bottom
    Change "Figure 18.20" to "Figure 18.19".
Page 476, Figure 21.7
    The light curve for Type II supernova should be shifted so that its peak intensity lies below that of the curve for Type I.
Page 479, 1st column, line 5 from bottom
    Note that except in a psychological sense, we cannot be overdue for events that are truly random, i.e., where the probability doesn't vary with time. For events where the probability increases with time, e.g. an earthquake fault whose stress is building up, or a particular massive star whose core has been accumulating heavy elements for some time, the idea of being overdue could apply.
Page 480, 2nd column, line 7 from bottom
    The element Technetium does in fact occur naturally on Earth. It was discovered in 1925 in columbite ore by Ida Tacke and her colleagues in Germany. It can also be found in Uranium ore.
Page 488, Figure 21.17
    The half lives given in the figure are wrong. For Nickel-56 it should be 6.1 days, and for Cobalt-56 it should be 77 days.
Page 508, 2nd column, line 7 from bottom
    Change "574" per century" to "5600" per century".
Page 526, 1st column, line 12 from bottom
Page 529, 1st column, line 9 from bottom
    The sun's distance from the center of the Galaxy, although not known exactly, was given a working value of 8.5 kpc by the International Astronomical Union in 1982.
Page 626, Figure 27.1
    The figure contains some errors. The radiation density and the matter density do decrease at different rates as time increases, however in a log-log plot the relations are straight lines only when the horizontal axis is the "scale size", R, of the universe. If the axis is time, as in the figure, then the slopes of the relations change at the crossover from radiation-dominated to matter-dominated, creating knees in the curves. Interestingly, for a Euclidean universe, the slope of the radiation density in the radiation-dominated region matches the slope of the matter density in the matter-dominated region.
Page 629, Table 27.1
    Change Density of 3X1025 to 3X10-25
Page 636, 1st column line 12
    Change "Grand Unified Terories" to "Grand Unified Theories"
Page 637, Figure 27.12
    Change "(a) Time = 10-39s" to "(a) Time = 10-35s"

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