Astronomy Chapter 1-11
Astronomy HOMEWORK Chapter 1 9th ed 5. In Figure 1-8, what is another name for the “Sun’s annual path?” Ecliptic. This term also refers to the mathematical plane of Earth’s orbit. 10. By about how many degrees does the Sun move along the ecliptic each day? The Sun moves 360 degrees in 365.25 days along the ecliptic, so Degrees per day = (360◦ )/365.25 days = 0.986◦ = 1◦ . Round to 1 degree since the question says “about how many...” 14. What are the vernal and autumnal equinoxes? What are the summer and winter solstices? How are these four events related to the ecliptic and the celestial equator? The equinoxes are the points on the celestial sphere where the ecliptic and celestial equator intersect. The vernal equinox is the point where the sun crosses the celestial equator northbound.
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These events mark the start of the seasons; the equinoxes occur on or about March 21 and Sep 22, while the solstices occur on or about June 21 and December 21. 25. How is an annular eclipse of the Sun different from a total eclipse? What causes this difference? In both annular and total solar eclipses, the Moon lines up precisely with the Sun, center on center. The difference is that in an annular eclipse, the Moon fails to cover the Sun completely, leaving a bright ring. This is caused by the Moon being farther away than usual – its orbit isn’t exactly circular – so that its angular size is smaller. Variation in the distance to the Sun also contributes, since Earth’s orbit is likewise not precisely circular. But the variation in Moon angular size is greater. 27. At what phase(s) of the moon does a solar eclipse occur? A lunar
These events mark the start of the seasons; the equinoxes occur on or about March 21 and Sep 22, while the solstices occur on or about June 21 and December 21. 25. How is an annular eclipse of the Sun different from a total eclipse? What causes this difference? In both annular and total solar eclipses, the Moon lines up precisely with the Sun, center on center. The difference is that in an annular eclipse, the Moon fails to cover the Sun completely, leaving a bright ring. This is caused by the Moon being farther away than usual – its orbit isn’t exactly circular – so that its angular size is smaller. Variation in the distance to the Sun also contributes, since Earth’s orbit is likewise not precisely circular. But the variation in Moon angular size is greater. 27. At what phase(s) of the moon does a solar eclipse occur? A lunar