Chapter 20

The Solar System

http://www.brainpop.com/science/space/solarsystem/

Earth at the center-Centuries ago, the sun and stars moved across the sky while Earth seemed to remain stationary (still).Greek Observations-several points of light seemed to wander across the sky among the stars. They called these PLANETS.

Mercury, Venus, Mars, Jupiter, SaturnThey thought that Earth was in a rotating dome called a celestial sphere.

Section 1-Observing the Solar System

Geocentric- an Earth centered model of the solar system“geo” -EarthGeocentric System-Earth is at the center of the revolving planets and stars.

A.D. 140- Greek astronomer Ptolemy developed the geocentric modelAstronomer- a scientist who studies the universe beyond Earth.His model had the Earth at the center with other planets moving on smaller circles that move on bigger circles.This model was incorrect but showed how motions of planets are observed.This geocentric model was accepted for over 1,500 years!

Ptolemy’s Model

Not everyone believed the Earth being at the center.Heliocentric was developed as the sun being the center of the solar system“helios” – sunIn the heliocentric system, the Earth and other planets revolved around the sun. People did not want to believe this system because it went against Earth being the center of the universe.

Sun at the Center

In a heliocentric system, Earth and the other planets revolve around the sun.

http://www.astro.utoronto.ca/~zhu/ast210/both.html

1543- Nicolaus Copernicus further developed the heliocentric modelCopernicus was able to work out the arrangement of the known planets and how they move around the sun.Because this was against the church and the belief of the time, and Copernicus did not have enough evidence to support this idea, he did not publish his theories until after his death.

Copernican Revolution

1610- Galileo Galilei used newly invented telescope to make discoveries that supported the heliocentric model. He saw 4 moons revolving around Jupiter (proved not everything revolved around the Earth)He also saw that Venus goes through phases similar to Earth’s moon which it would not have if it circled around the Earth.The Heliocentric Model must be correct!

Galileo’s Evidence

Copernicus correctly placed the sun as the center of the universe but incorrectly assumed the planets travel in orbits that are perfect circles.Late 1500’s- Tycho Brahe and assistants studied and recorded the positions of the planets for 20 years without telescopes!After Brahe died in 1601, his assistant Johannes Kepler continued analyzing observations.

Tycho Brahe’s Observations

By studying Mars, Kepler found that Mar’s orbit was an ellipse instead of a circle.Ellipse- oval shape that is closely circularUsing the evidence gathered by Brahe, Kepler found that the orbit of each planet is an ellipse.

Kepler’s Calculations

Since Galileo’s time, our knowledge of the solar system has increase dramatically.We have discovered 3 more planets- Uranus, Neptune, and PlutoAstronomers have discovered other objects in the solar system like comets and asteroids.Today we know that the solar system consists of the sun, nine planets and their moon, and several kinds of smaller objects that revolve around the sun. Galileo used a telescope to make observations as we do today but we have more technology and have placed telescopes in space as well as space probes to explore further into the far reaches of our solar system.

Modern Discoveries

Section 2The Sun

https://www.youtube.com/watch?v=HEheh1BH34Q

The sun does not have a solid surface, but is a ball of glowing gas¾ mass is hydrogen, ¼ heliumLike the Earth, has an interior and atmosphereThe sun’s interior consists of the core, the radiation zone, and convection zone.

The Sun’s Interior

https://www.youtube.com/watch?v=gS1dpowPlE8 (how does the sun work?)

3 parts of the sunThe core- or ‘central region’Energy comes from nuclear fissionNuclear fission- a process where hydrogen atoms join together to form helium. -this only occurs under extremely high pressure and temperature-temperature in the core- 15 million degrees Celsius (27 mill. F)Energy slowly moves out from the core into space.

The radiation zone- ‘middle layer’ a region of very tightly packed gas where energy is transferred mainly in the form of electromagnetic radiation. Energy can take 100,000 years to move through this layer.The convection zone- ‘outer most layer’ hot gases rise to the top from the bottom, cool, then sink forming loops of gas that move energy to the surface.

Includes the photosphere, chromosphere, and the coronaThe Photosphere- (inner layer) (‘photos’ – light) the sphere that gives off visible light. Considered the sun’s surface layerThe Chromosphere- (middle layer) (‘chroma’ – color) the sphere of colorThe Corona- (outer layer) (‘corona’ – crown) extends into space and thins into streams of electrically charged particles called solar wind.

The Sun’s Atmosphere

Features on or just above the sun’s surface include sunspots, prominences, and solar flares.https://www.youtube.com/watch?v=HFT7ATLQQx8Sunspots- areas of gas on the sun’s surface that are cooler than the gases around them. Cool areas don’t give off much light and are darker.

Features on the Sun

huge reddish loops of gas (sunspots) extending over the edge of the sun

Prominences-

when loops connect releasing magnetic energy, erupting into space.

Solar flares-

Solar flares increase solar wind from the corona, which reach Earth’s upper most part of the atmosphere. Normally blocked from Earth’s magnetic field and atmosphere, at the North and South poles, particles create powerful electric currents causing gas molecules to glowAurora- rippling sheet of light caused by solar flaresSolar wind particles effect Earth’s magnetic field creating magnetic storms, disrupting radio, tv, phone, and electrical power problems.

Solar wind

https://www.youtube.com/watch?v=Ip2ZGND1I9Q (aurora)https://www.youtube.com/watch?v=2zOlkIyg3iE (solar wind)https://www.youtube.com/watch?v=3JdWlSF195Y (song-why does the sun shine?)

Section 3

The Inner Planets

Mercury, Venus, Earth, and MarsThe 4 inner planets are small and have rocky surfacesInner planets are also called terrestrial planets

4 inner planets

Characteristics:Water: Liquid water on the surface70% covered Exists in all three forms: solid, liquid, and gasAtmosphere: Has enough gravity to hold gasesNitrogen- 78% Oxygen- 20% and other gases such as Argon and Carbon Dioxide and water vapor.

Earth

The smallest terrestrial planet and closest to the sunCharacteristics:A single probe called Mariner 10 in the mid 1970’s showed the surface with craters and plainsThe surface has changed little over time.

Mercury

http://www.space.com/20086-mercury-map-nasa-messenger.html

https://www.youtube.com/watch?v=6KY-oB2i9lo

Mercury’s Atmosphere:Almost NONE!Small mass of the planet- weak gravityExtreme temperatures- Greatest out of all planetsDuring the day the surface reaches 430°C, at night (because of lack of atmosphere heat escapes to space) temp goes to -170°C

Size and mass similar to Earth and referred to as Earth’s twin or Sister planetDensity and internal structure similar to Earth’s.Takes 7.5 Earth months to rotate around the sun and 8 months to rotate around on its axis. A day on Venus is longer than a Venus year!Rotates East to West

Venus

https://www.youtube.com/watch?v=HqFVxWfVtoohttp://www.youtube.com/watch?v=hsgrTnTTPpc (space school)

Venus’s Atmosphere:Super thick and always cloudyMade mostly of sulfuric acid.Atmosphere is 90 times greater than Earths and would crush you if you stood on Venus’s surface. Carbon Dioxide traps heat in through the greenhouse effectTemperature average: 460°C- hot enough to melt lead.

Probes have visited Venus.Venera- 1970, Magellan- 1990 mapped entire surfaceCovered with rock with volcanoes and plains formed by lava flows

Venus Continued

“Red Planet”- iron rich rocksAtmosphere: More than 95% Carbon Dioxide- similar to Venus but thinnerYou could walk on Mars but would need a tank of oxygenFew clouds and temperatures range from -140°C to 20°C

Mars

https://www.youtube.com/watch?v=i5D8e71c75U (living on mars)

https://www.youtube.com/watch?v=XmxaPKt94jI (how mars lost its atmos)

Mars’s Water:Scientist think large amounts of water flowed on Mars’s surface in the distant past.The atmosphere is so thin that any water will turn to gas.Two frozen polar ice caps Water may be frozen underground. Mars’s Seasons:Axis is tilted – has seasons like Earth Northern and southern poles have different season so one ice cap grows and the other shrinks.Windstorms cause dust to blow around

Many space probes have visited Mars.NASA’s Spirit and Opportunity rovers have explored and examined rocks and soil samples, finding strong evidence of liquid water.Several volcanoes flowed in Mars’s past but are inactive now. Olympus Mons is the largest volcano in the solar system.

Exploring Mars

https://www.youtube.com/watch?v=B8OUL9QYNpI (curiosity)

https://www.youtube.com/watch?v=nQfJ7j2UGGk (planet rap)

Section 4

The Outer Planets

The first 4 outer planets- Jupiter, Saturn, Uranus, and Neptune- are much larger and more massive than Earth.They do not have a solid surface and often called Gas Giants.The 5th planet, Pluto, is small and rocky like the terrestrial planets. Gas Giants-Composed of hydrogen and helium in liquid formStrong gravitational force compared to terrestrial planetsOuter layers are extremely cold, inner layers temperatures increaseHave many moonsAll have rings-small particles of ice and rock

The largest and most massive planetAtmosphere: Made of hydrogen and heliumThe Great Red Spot- a storm larger than Earth, similar to a hurricane, and first observed in the mid-1600’s.

Jupiter

Structure:Dense core of rock and ironThick mantle made of liquid hydrogen and heliumCrushing weight of atmosphere- 30 million times stronger than Earth. Jupiter’s Moons:Galileo discovered Jupiter’s 4 largest moons- Io (has active volcanoes), Europa (icy crust covers liquid oceans), Ganymede (largest moon in solar system; larger than Mercury), and Callisto (covered with craters).Dozens of others orbit around Jupiter

Second largest planet in solar system.Only planet that is less dense than

water (it will float)

Atmosphere: Mainly hydrogen and heliumClouds and storms (hurricane discovered recently at the north pole)Rings: (chunks of rock and ice)Has most spectacular than any other planetBroad and thin like a compact discMoons: Largest-Titan

Saturn

First, let’s get something straight-

Uranus

Uranus: Gas Giant, planet near the end of our solar system.

Your Anus: Human biology- organ near the end of the digestive system.

Comparison

Uranus Atmosphere: Looks blue-green because of methane in atmosphereHas ringsDiscovering Uranus: 1781-William Herschel opened up the door for active solar system study

Exploring Uranus:Voyager 2 arrived and sent back close-ups showing only a few cloudsUranus rotates in 17hrsUranus’s axis is tilted at 90 degrees from its vertical. (rotates top to bottom instead of side to side)Believed a large object hit into Uranus and knocked it on its side.Uranus Moons:5 largest have icy, cratered surfacesSome have lava flowsTotal of about 27 moons.

Cold, blue planet with visible cloudsCould be slowly shrinking, heating up interior, producing clouds and storms in atmosphere.Discovery: First as a mathematical prediction based on Uranus’s orbit. Thought gravity of an unseen planet was affecting Uranus and discovered in 1846.

Neptune

Exploring Neptune:Voyager 2 discovered a Great Dark Spot, like Jupiter’s Great Red Spot, but did not last long. Spots seem to come and go.Moons: 13 moons- largest Triton(thin atmosphere and south pole covered with nitrogen ice)

Very different than gas giantsPluto has a solid surface, much smaller and dense than outer planets.Has a single moon: Charon which is more than half the size of Pluto and sometimes called a double planet.Pluto’s orbit:Takes 248 Earth years to revolve around the sun!Very elliptical, brings it closer to the sun than Neptune

Pluto

Pluto is very small Pluto may only be slightly larger than some of the other pieces of ice, rock, and dust that orbit in our solar system. If astronomers had discovered these other objects, it may not have been called a planet.Recently astronomers have discovered a larger body beyond Pluto but have not classified or named this as a planet yet.

Is Pluto a planet?