Solar System Astronomy

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Patterns in the Sky :

Patterns in the Sky Solar System Astronomy Chapter 2

Motions in the Sky :

Motions in the Sky The Sun and stars show regular patterns of motion which reflect the motion of the Earth. are clues to how the Solar System works. Our focus: Daily rotation of the Earth Annual orbit of the Earth Monthly orbit of the Moon

Frames of Reference :

Frames of Reference An observer sees things from a frame of reference. On the Earth, different observers see different parts of the sky. different motions of the stars. This shows the Earth is a sphere and rotates daily.

Constellations :

Constellations Constellations are arbitrary patterns of stars in the sky. During the year, the Sun passes in front of some constellations. The annual path of the Sun is called the ecliptic. The constellations along the ecliptic are called the zodiac.

Constellations & such… :

Constellations & such… SummerTriangle Orion Ursa Major Scorpius Canis Major Centaurus Taurus Leo Crux Andromeda Aries Sagittarius Pisces Pegasus Argo Libra Boötes

The Celestial Sphere :

The Celestial Sphere It helps to think of the sky as the celestial sphere. The stars, Sun, and planets are actually at different distances. The celestial sphere rotates around the north and south celestial poles each day. Midway between the poles is the celestial equator.

Celestial Sphere and Ecliptic :

Celestial Sphere and Ecliptic

Celestial Sphere, Ecliptic, &c :

Celestial Sphere, Ecliptic, &c

At the North Pole :

At the North Pole An observer would see half the celestial sphere. The north celestial pole is overhead. The stars rotate counterclockwise in about 24 hours. No star rises or sets: all are circumpolar.

At the Equator :

At the Equator All stars rise and set. The celestial poles are on the northern and southern horizons. Observers can see the whole celestial sphere as it rotates.

In Between (like Radford) :

In Between (like Radford) One pole is above the horizon. The angle to the horizon equals the latitude. Some stars are circumpolar; others rise and set. Some of the celestial sphere is never visible.

Rotation of the Earth :

Rotation of the Earth The motion of the celestial sphere reflects the daily spin of the Earth. The rotation of the Earth sets the spin of hurricanes (Coriolis effect). Storms spin counterclockwise in northern hemisphere, clockwise in the southern.

Annual Motion of the Sky :

Annual Motion of the Sky The changing position of the Sun reflects the Earth’s orbit around the Sun. As the Earth’s position changes, the Sun is seen against different constellations.

The Earth’s Axis & Rotation :

The Earth’s Axis & Rotation The Earth’s axis is not perpendicular to the ecliptic plane. 23.5˚ Sun is alternately north and south of the celestial equator during the year. Produces seasons receive more direct sunlight in the summer, and Sun is up longer

The Earth’s Axis & Rotation :

The Earth’s Axis & Rotation

Special Days of the Year :

Special Days of the Year Apparent Motion of the Sun Summer solstice: Sun farthest north. Autumnal equinox: Sun on the equator, moving southward. Winter solstice: Sun farthest south. Spring (vernal) equinox: Sun on the equator, moving northward.

The Earth Spins and Revolves :

The Earth Spins and Revolves

Precession :

Precession Gyroscopic Effect The location of the celestial poles slowly shifts. Currently the north celestial pole is near the bright star Polaris. This reflects a 26,000-year wobble in the Earth’s spin axis.

Solar Eclipse About 1/year – rare. Applause

Last look at lunar cycle :

Last look at lunar cycle