Astronomy summative 2

Astronomy

Eccentricity and Motions of the Earth

Summative part 2

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Johannes Kepler

Kepler found flaws in the Heliocentric model of the solar system.

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Johannes Kepler

The planets could NOT be traveling in perfect circles around the Sun.

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Johannes Kepler

He developed three laws known as Kepler’s Laws of Planetary Motion

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Kepplers Laws

Third Law

Second Law

First Law

(Law of Areas) As a planet moves around the Sun in its orbit, it covers equal areas in equal time. (changes speed)

(Law of Orbits) The orbit of each planet around the Sun is an ellipse. The Sun is at one focus.

(Law of Periods) The time it takes a planet to complete one orbit around the Sun is related to its average distance from the Sun. (p2 = a3, p = time, a = dist. from sun)

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Eccentricity

Eccentricity is how flat or circular an ellipse is.

It ranges from 0 – 1 0 = circle 1 = line Earth’s orbit has an eccentricity value of 0.017. This tells us that Earth’s orbit is nearly circular.

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EdPuzzle Time

Axial Tilt

The Earth’s axis of rotation is now tilted 23.5˚.

These changes in the axial tilt is believed to be the cause for Ice Ages.

Over 41,000 years the tilt varies from 22.1˚ to 24.5˚

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Motions of Earth

Rotation – spinning of a body on its axis

Causes day and night 24 hour period (time zones)

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Motions of Earth

Revolution – object traveling along a path around some point in space

365.25 days

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Motions of Earth

Perihelion – when the earth is closest to the sun (Jan. 3)

Aphelion – when the earth is furthest from the sun (July 4)

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Motions of Earth

Ecliptic – The apparent annual path of the Sun against the backdrop of the celestial sphere

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Astronomy

Solstice and Equinox

Summative part 2

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Equinox

Solstice

Autumnal Equinox – Sep. 23

• Night and day are same length
• First day of fall

Spring Equinox - March 21

• Night and day are same length
• First day of spring

Winter Solstice – Dec. 21

• The Sun is the lowest in the sky
• Shortest day of the year
• First day of winter
• Tropic of capricorn (23.5°S)

Summer Solstice – June 21 –

• The Sun is the highest in the sky (N.H)
• longest day of the year
• First day of summer
• Tropic of cancer (23.5° N) – Sun directly overhead (zenith)

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Precession

The Earth wobbles like a spinning top.

This wobbling is called precession.

This is caused by the gravitational pull of the Moon and the Sun

It takes 25,725 years for the Earth to wobble through one complete cycle.

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Orbital Precession

The Earth’s orbit is revolving around the Sun.

This is called the orbital precession.

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Combined Effects

The combined effects of the axial and orbital precessions will make our seasons as we know them today more extreme.

Winters will be colder

Summers will be hotter.

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Inclination

Orbital plane – the first 8 planets are all fixed in the same plane.

Pluto however is tilted 17.1˚ from the rest of the planets.

This tilt is called inclination.

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Astronomy

Summative

Summative part 2

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