The Celestial Sphere

2/3/09

Mastering Astronomy Assignment 2 Constellations – the 88 semi-rectangular regions that make up the sky • Due Feb 10, 11 am • Northern constellations have Latinized • Read Chapter 1 Greek-mythology names: – Orion, Cygnus, Leo, Ursa Major, Canis Major, Canis Minor • Southern constellations have Latin names: – Telescopium, Sextans, Pyxsis

What do you think? What do you think?

• Do the stars stay in the same position in the • What causes the stars move? sky all day/night long? • Do the stars actually move in the way they • Do we see the same stars all year round appear from Earth? every night? • Is the daily motion of the Sun different from the stars?

Earth’s daily rotation and yearly orbit The Celestial Sphere

• The north celestial pole (NCP) • The south celestial pole (SCP) • The celestial equator • The ecliptic • Right ascension – like longitude • Declination – like latitude

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The Celestial Sphere The Milky Way

A band of light The 88 official making a circle constellations around the celestial cover the celestial sphere. sphere. What is it? Our view into the plane of our galaxy.

Our view from Earth: The Local Sky • Stars near the north celestial pole are circumpolar and An object’s altitude (above horizon) and direction never set. (along horizon) speciﬁes its location in your local • We cannot see stars near the south celestial pole. sky • All other stars (and Sun, Moon, planets) rise in east and set in west.

A circumpolar star never sets

Celesal Equator

Your Horizon This star never rises

Celestial Sphere In-class Activities: Position Rotation Star B 2 Star A 1 2 • Work with a partner! Celestial Celestial Sphere 3 Sphere • Read the instructions and questions carefully. 1 4 • Discuss the concepts and your answers with one 3 another. Take time to understand it now!!!! Horizon • Come to a consensus answer you both agree on. 4 • If you get stuck or are not sure of your answer, ask another group. Celestial Sphere • If you get really stuck or don’t understand what the Rotation question is asking, ask me.

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Is the horizon shown a real physical horizon or an Celestial Sphere Rotation imaginary plane that extends In what direction Star B from your observing location 2 Star A and Earth out to the stars? Celestial Sphere is the observer 1 2 Rotation Star B Celestial Sphere Celestial Sphere facing? 3 Can the observer shown see a 2 Star A 1 star when it is located below 1 2 4 the horizon? Why or why not? Celestial Celestial 3 Sphere 3 Sphere 1 a) toward the South Horizon Is there a star that is in an unobservable position? 4 b) toward the North 4 3 Horizon c) toward the East When a star travels from a d) toward the West Celestial Sphere position below the observer’s Rotation 4 horizon to a position above the horizon, is that star rising or setting? Celestial Sphere Rotation

Imagine that from your current location you Celestial Sphere observe a star rising directly in the east. When this Where would the Rotation Star B star reaches its highest position above the horizon, observer look to see 2 Star A where will it be? 1 2 the star indicated by Celestial Celestial Sphere 3 Sphere the arrow? 1 A. high in the northern sky 4 3 B. high in the southern sky Horizon C. high in the western sky D. directly overhead A. High in the Northeast 4 B. High in the Southeast Celestial C. High in the Northwest Sphere D. High in the Southwest Rotation

Nightly Motion of the Stars

Earth’s rotation • Imagine looking Celestial Sphere Rotation Star B causes the Sun, toward the East as 2 Star A Planets, Moon a star rises above 1 2 Celestial Celestial Sphere 3 Sphere and stars to your horizon - 1 appear to move what does it do 4 after that? 3 when viewed Horizon from Earth 4

Celestial Sphere Rotation

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Nightly Motion of the Stars What direction • For stars (the Moon and planets) that is the observer appear in the southern sky: Stars first rise facing in this near the eastern horizon, move upward and toward the south, and then move down and picture? set near the western horizon. A. North B. South C. East D. West

Nightly Motion of the Stars Nightly Motion of the Stars Celestial Sphere Rotation Star B 2 Star A • Imagine looking toward the North. What 1 2 Celestial Sphere Celestial Sphere do stars appear to do over the course of 3 1 an evening? 4 3 Horizon

Celestial Sphere Rotation

Looking North: Circumpolar Stars Nightly Motion of the Stars

• Looking North: Stars – Circumpolar stars seem to move counter-clockwise appear to move around the stationary North Star. counter-clockwise – These constellations and stars are visible any night of the around the stationary year in the NORTHERN sky because they never rise or North Star (Polaris) – set! we call these – Examples: Ursa Major, Ursa Minor, Draco, Cepheus, and Cassiopeia circumpolar stars.

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What happens over time in the Northern Sky? How long did it take to get this picture?

Take out a piece of paper and put your name on it along with your answer!!

In-class Activities: Motion

• 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.