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Why don’t we see the same Mastering Astronomy Assignment 3 constellations throughout the year?
• Due Feb 17, 11 am • Read Sections 2.1, 2.2 and S1.2
The Earth also revolves around the Sun, From our perspective... which changes our view of the stars
March September
Earth circles the Sun in 365.25 days and, The Ecliptic consequently, the Sun appears to go once around the ecliptic in the same period. If we could see • As the Earth orbits background stars in the daytime, our Sun would the Sun, the Sun appears to move a) appear to move against them at a rate of 360° per eastward among the day. stars following a path b) appear to move against them at a rate of about called the ecliptic 15° per day. • The ecliptic is a c) appear to move against them at a rate of about 1° projection of Earth’s per day. orbit onto the The tilt of the Earth's axis d) remain stationary against these stars. celestial sphere causes the ecliptic to be tilted to the celestial equator
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The sky varies as Earth orbits the Sun
• As the Earth orbits the Sun, the Sun appears to move along the Zodiac ecliptic. • At midnight, the stars on our meridian are opposite the Sun in The 13 Zodiacal constellations that our Sun the sky. covers-up (blocks) in the course of one year (used to be only 12) • Aquarius • Leo • Pisces • Libra • Aries • Virgo • Scorpius • Taurus • Ophiuchus • Gemini • Sagittarius • Cancer • Capricornus
The Zodiacal Constellations that our Sun blocks in the course of one year (only 12 are shown here) North Star
Aquarius Pisces Capricornus Aries 1 day Sagittarius
Taurus Scorpius
365 days Libra Gemini Virgo Cancer Leo
North Star
Aquarius Pisces Capricornus In-class Activities: Seasonal Stars Aries 1 day Sagittarius • Work with a partner! Taurus Scorpius • Read the instructions and questions carefully. 365 days • Discuss the concepts and your answers with one Libra Gemini another. Take time to understand it now!!!! Virgo Cancer Leo • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask Taurus another group. Aries Gemini • If you get really stuck or don’t understand what the question is asking, ask me. South Cancer Pisces
What it would look like if you were the observer
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North Star North Star
Aquarius Aquarius Pisces Capricornus Pisces Capricornus Aries Aries 1 day Sagittarius 1 day Sagittarius
Taurus Scorpius Taurus Scorpius
365 days 365 days Libra Libra Gemini Gemini Virgo Virgo Cancer Leo Cancer Leo What is the name of the constellation that would What time is it for the observer? appear on the observers Eastern Horizon? a) noon a) Cancer b) 6am b) Gemini c) Midnight c) Taurus d) 6pm d) Aries e) Pisces
North Star North Star
Aquarius Aquarius Pisces Capricornus Pisces Capricornus Aries Aries 1 day Sagittarius 1 day Sagittarius
Taurus Scorpius Taurus Scorpius
365 days 365 days Libra Libra Gemini Gemini Virgo Virgo Cancer Leo Cancer Leo Two months from the time shown what constellation will Two months from the time shown, which constellation be high in the Southern sky, at Midnight? would the Sun be? a) Taurus a) Scorpius b) Cancer b) Pisces c) Pisces c) Capricornus d) Virgo d) Virgo
If you could see stars during the day, the drawing below How can we describe the motion of the sun in the sky? shows what the sky would look like at noon on a given day. The Sun is near the stars of the constellation Gemini. Near meridian which constellation would you have expect the Sun to be zenith located at sunrise on this day?
Sun 1. Leo
2. Cancer Gemini LUNCH!! AM or ante PM or post Cancer Taurus 3. Gemini meridian meridian 4. Taurus Leo Aries 5. Aries ⇐ East South West ⇒
east south west
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Where is the Sun at noon today? Noon zenith
• Noon is the precise moment when the Sun is here or highest in the sky (on the meridian) and the there? sundial casts its shortest shadow. • Sun highest in the sky ≠ clocks read 12 pm
east south west
Where is the Sun at noon today? What about the path of the Sun?
zenith zenith
What about What about there tomorrow at tomorrow at there noon? noon? JUST A LITTLE HIGH !!
east south west east south west
The time for Where is the Sun throughout the year? the sun to go from being Mar 21 zenith June 21 zenith ONE (Vernal) and Summer highest in Sept 21 Solstice the sky at (Autumnal) noon, to YEAR Equinox lowest and back to highest again is…
Dec 21 Winter Solstice
east south west east south west
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Position of the Sun when photographed during Sun’s altitude changes with seasons the day of the winter and summer solstice
Sun’s position at noon in summer
Sun’s position at noon in winter
In-class Activities: Path of the Sun
• Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. Take time to understand it now!!!! • Come to a consensus answer you both agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the question is asking, ask me.
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