Astronomy Notes The Universe ©Mark Place, 2008-2009 www.LearnEarthScience.com Revised 2009

How Old is the Universe? Astronomers estimate that the universe is somewhere between 12 and 14 billion years old. To put this in perspective, the Solar System is thought to be 4.5 billion years old and humans have existed as a genus for only a few million years.

What is the Big Bang Theory? The universe started as a single point. That point was extremely dense. It became unstable and exploded outward. Today the universe continues to expand.

What is the Doppler Effect?

The Doppler effect – As a star is moving away from us it appears RED because the wavelength of the waves is increasing. If a star is moving closer to us it appears BLUE because the wavelength of the waves would be decreasing- RED shift or BLUE shift. Stars appear red-MOVING AWAY!

Evidence for the Big Bang (1) The Doppler Effect

Shifts in the Electromagnetic Spectrum Doppler Effect ~~> Red Shift = stars moving away Blue Shift = stars moving towards

Evidence for the Big Bang (2) Cosmic Background Radiation

Stars ©Mark Place, 2008-2009 www.LearnEarthScience.com

What are the main classifications of stars? Blue Supergiants Red Giants Main Sequence White Dwarfs Red Dwarfs ESRTs p15

characteristics are used to What two characteristics are used to classify stars? Luminosity Temperature ESRTs p15

What type of star is our Sun classified as? ESRTs p15 Main Sequence

How do stars generate their energy? Hydrogen Helium Hydrogen Nuclear Fusion

Our Solar System ©Mark Place, 2008-2009 www.LearnEarthScience.com

The total mass of all the asteroids is less than that of the Moon. rocky objects with round or irregular shapes lie in a belt between Mars and Jupiter The total mass of all the asteroids is less than that of the Moon.

Comet A comet is a body of ice, dust and small rocky particles which orbits the Sun. When close enough to the Sun, a comet exhibits a visible tail. The popular Halley's comet next scheduled pass by the earth is in 2062.

shooting stars A meteor is a bright streak of light in the sky (a "shooting star" or a "falling star") produced by the entry of a small meteoroid into the Earth's atmosphere

The Planets

Draw a line across the table between the terrestrial and jovian planets and label. terrestrial jovian

Which are more dense? Jovian or terrestrial

Which have more moons ? Jovian or terrestrial

Which have longer periods of revolution? Jovian or terrestrial

Which are larger in size on average ? Jovian or terrestrial

Which planet has the longest day? Venus

Which planet has the longest year? Neptune

How are the orbits of the planets described? slightly, eccentric ellipse eccentricity website

Which planet has the least perfectly circular orbit? Mercury

Which planet has the most perfectly circular orbit? Venus

Calculate the eccentricity of the ellipse below: length of major axis Formula: eccentricity = distance between foci length of major axis

When does a planet move slowest in its orbit? When furthest from Sun When does a planet move fastest in its orbit? When closest to Sun

Kepler's Second Law Area A = Area B Area C eccentricity website

Explain the difference between the geo- and helio-centric models of the solar system. Helio-centric Geo-centric Earth- centered Sun- centered

Earth Motions Astronomy ©Mark Place, 2008-2009 www.LearnEarthScience.com

How long is one rotation of Earth? Earth's Motions How long is one rotation of Earth? One day How long is one revolution of Earth? One year

Rising and Setting of the Sun Rotation Rising and Setting of the Moon Movement of Stars through the sky Revolution Changing Constellations The Seasons

Seasons Earth tilted away from sun in winter Earth tilted towards sun in summer Earth tilted away from sun in winter Seasons Sun highest in sky in summer and lowest in sky in winter

Earth's rate of rotation? How do you calculate Earth's rate of rotation? One rotation = 360° Time for one rotation = 24 hours 360° ÷ 24 = 15°/hr

How many degrees did the stars move from diagram 1 to diagram 2? 30° (2 hours x 15°)

It’s the only one that didn’t move How can you find Polaris? It’s the only one that didn’t move

Because Polaris can only been seen in the North What hemisphere must you be in? Why? Northern Because Polaris can only been seen in the North

What direction must you be looking? North

What direction do the stars appear to move? (Look at diagram)

What causes the stars appear to move?

Evidence for Rotation Foucault Pendulum Coriolis Effect

Evidence for Revolution Changing Constellations Parallax -movement of stars

Phases of the Moon

What causes the phases of the moon? The moon's revolution around Earth.

27.3 days How long does one revolution of the moon take? How long does one rotation of the moon take?

What phenomenon does this explain? We only ever see one side of the moon.

Why does the moon rise later each day? because as the Earth rotates, the moon revolves

What phase of the moon is this? New Gibbous New Crescent 3rd Quarter

Approximate Times of Moonrise and Moonset    moonrise    moonset new moon 06:00 AM 06:00 PM waxing crescent 09:00 AM 09:00 PM first quarter 12:00 PM 12:00 AM waxing gibbous 03:00 PM 03:00 AM full moon waning gibbous third quarter waning crescent How many hours is the moon visible each day? 12 hours

What is "waxing"? more of the moon's surface can be seen

What is "waning"? less of the moon's surface can be seen

The phases of the moon are what type of event? Cyclic

A Total Solar Eclipse over Turkey

solar and lunar eclipses? What’s the difference between solar and lunar eclipses? Solar Lunar Earth goes into moon’s shadow moon goes into Earth’s shadow

New Moon Eclipses Full Moon

Solar Eclipse 2009

Solar Eclipses through 2020

Lunar Eclipse 2009

solar and lunar eclipses Why don’t we have solar and lunar eclipses every month? The moon’s orbit is tilted 5° from the Earth’s orbit.

Our Galaxy- The Milky Way                          The End