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Passport Science Space Unit –

Part 2 of 3 PowerPoints

(Textbook reference Chapters 12, 13, 14, 15 and 16)

The Sun (Textbook reference 14-2

• The sun is an ordinary star.• The sun is the biggest,

brightest, and hottest object in the solar system.

• Its energy is the result of the fusion of hydrogen nuclei into helium nuclei.

• The sun is made of about 70% hydrogen and 28% helium.

Source: The British Astronomical Association

Our Sun is a star that has already spentabout 5 billion years on the main sequence.

Scientist believe our Sun is roughly halfwaythrough it's life.

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Characteristics of the Sun• Interior: Core, Radiation Zone, Convection

Zone• Exterior: Photosphere, Chromosphere, Corona• Features: Sunspots, Prominences, Solar Flares• Central star in our solar system around which

planets revolve• Composed of gases (H2 and He) burning at

15,000,000 o C

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The Sun: Seasons (Textbook Reference 12-1)

Seasons: Solstices

sun directly overheadtwo times a year (June 21 and December 21)June=longest day, December=shortest day

Equinoxeshalfway between solsticesneither hemisphere is tilted toward the sundaylight and darkness=equal

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What causes the seasons?

1. 23.5° tilt of Earth’s axis2. Direct vs. indirect sun

rays3. Length of daylight

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Winter

FallSummer

Spring

Sun

In one year the earth revolves around the sun one time.

For every time Earth rotates on

it’s axis, one day passes.

In one year the earth rotates on its axis one 365

times.

Which season is it when the south end of Earth’s axis is tilted toward the sun?

Stars are the source of light for all objects in outer space

Earth’s Moon

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Phases of the Moon (Textbook reference 12-3)

waxing = increasing waning = decreasing

gibbous = > ½ crescent = < ½

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Lunar Phases• New Moon

New

Waxing CrescentFirst QuarterWaxing GibbousFull

• Waxing Crescent

• First Quarter

• Waxing Gibbous

• Full Moon

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Lunar Phases• Full Moon • Waning Gibbous

• Last Quarter

• Waning Crescent

• New Moon FullWaning GibbousLast QuarterWaning CrescentNew

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Rotate vs. Revolve

• Rotation – spin of an object on its axis

• Revolution – orbit of an object around another object

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Moon’s Orbit and Phases

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Why does one side of the moon always face us?

• Moon rotates once every 27.3 days

• Moon revolves once every 29.5 days

• Moon’s rotation approximately equal to its revolution

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Eclipses

1. Lunar Eclipse 2. Solar Eclipse3. Total Eclipse

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A total eclipse of the sunoccurs during the day!

Only the corona is visible.

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Tides

•Effect of gravity between the moon and the sun

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Spring Tides• When the sun, the moon, and the Earth are all aligned in a 180o angle

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Neap Tide• When the sun, the moon, and the Earth form a 90° angle