Chapter 20: Problem 2
. Horizontal-branch stars are sometimes referred to as "helium main-sequence stars." In what sense is this true?
Chapter 20: Problem 2
. Horizontal-branch stars are sometimes referred to as "helium main-sequence stars." In what sense is this true?
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Get started for freeUse the Starry Night Enthusiast \({ }^{\text {TM }}\) program to show the location of Supernova \(1987 \mathrm{~A}\). In the menu, select Favourites \(>\) Deep Space \(>\) Local Universe to display the Milky Way and other nearby galaxies, conveniently labeled, against the background of distant galaxies, from a distance of \(0.282\) Mly from the Sun. (If the Milky Way does not appear immediately, click once on either of the Zoom buttons.) Remove the image of the astronaut's feet by clicking on View > Feet. You can rotate the Milky Way Galaxy and its neighbor galaxies by holding down both the Shift button and the mouse button while moving the mouse. (On a two-button mouse, hold down the left mouse button.) (a) Use the Find pane to locate and center the Sun in the field of view. Describe the position of the Large Magellanic Cloud (LMC), within which SN \(1987 \mathrm{~A}\) lies, relative to the Milky Way Galaxy and to our solar system. (b) Use the Find pane to center on the LMC. You should be able to locate the Tarantula Nebula, shown in Figure 20-17. Is SN 1987A near to the center or the edge of the LMC? (Note that, although Starry Night Enthusiast \({ }^{\mathrm{TM}}\) depicts the LMC as being rather flat, it is thought to be an irregular blob of stars with some thickness.)
. What is the asymptotic giant branch? Where is it located on an H-R diagram? How do asymptotic giant branch stars differ from red giants or main-sequence stars?
The similar names white dwarf, red dwarf, and brown dwarf describe three very different kinds of objects. Suggest better names for these three kinds of objects, and describe how your names more accurately describe the objects' properties.
Although they represent a fleeting stage at the end of a star's life, planetary nebulae are found all across the sky. Some of the brightest are listed in the accompanying table. Note that the distances to most of these nebulae are quite uncertain. Observe as many of these planetary nebulae as you can on a clear, moonless night using the largest telescope at your disposal. Note and compare the various shapes of the different nebulae. In how many cases can you see the central star? The central star in the Eskimo Nebula is supposed to be the "nose" of an Eskimo wearing a parka. Can you see this pattern?
Is a carbon star a star that is made of carbon? Explain.
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