Sun’s right ascension and declination – pick the comprehensive correct set Which of the following statements about the Sun’s right ascension (RA) and declination (δ) are correct?
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AThe Sun’s RA increases from 0 h toward 24 h as it returns to the first point of Aries
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BThe maximum declination north is about +23.5° around June 21 (June solstice)
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CThe Sun’s declination is 0° on about September 22–23 (autumnal equinox)
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DThe maximum declination south is about −23.5° around December 21–22 (December solstice)
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EAll of the above
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Right ascension and declination describe the Sun’s position on the celestial sphere relative to the equator and the vernal equinox. Seasonal motion causes predictable changes in δ and steady eastward progression in RA.
Given Data / Assumptions:
- Standard astronomical year with equinoxes near March 20–21 and September 22–23, solstices near June 21 and December 21–22.
- Obliquity of the ecliptic ≈ 23.5°.
Concept / Approach:As Earth orbits the Sun, the apparent solar position moves along the ecliptic. RA increases continuously and wraps at 24 h near the vernal equinox direction. Declination reaches +23.5° at the June solstice, 0° at both equinoxes, and −23.5° at the December solstice.
Step-by-Step Solution:(a) RA behavior: increases 0–24 h over a year → correct.(b) Maximum north declination ≈ +23.5° near June 21 → correct.(c) δ = 0° at September equinox → correct.(d) Maximum south declination ≈ −23.5° near December solstice → correct.Thus, all statements are correct.
Verification / Alternative check:Almanacs and solar ephemerides list RA and δ values matching these seasonal markers.
Why Other Options Are Wrong:Since (a)–(d) are all correct, any single-option choice would be incomplete; the comprehensive choice is “All of the above”.
Common Pitfalls:Mixing up which equinox corresponds to northward or southward crossing; RA increases uniformly while δ oscillates between ±23.5°.
Final Answer:All of the above