the solar system. what is the solar system? the solar system includes our sun, and all the matter...

The Solar System

What is the Solar System?

• The solar system includes our sun, and all the matter that orbits the sun.

• Planets, moons, dust and other debris

• People used to believe that everything they saw in the sky revolved around earth and therefore the entire Universe was our solar system.

Aristotle

• Greek Philosopher (384-322 BCE)• Came up with the idea that the earth was in the

center of the solar system– Geocentric Model

• Determined Universe to be spherical and limited in size

• This idea was adopted by the church and remained untested for 1000 years.

• His model was not very accurate and did not explain a lot of the variation seen in planets and comets.

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Ptolemy

• Greek Astronomer (87-150 CE)• Ptolemy looked at the motion of the stars and

the planets and came up with ideas that helped Aristotle’s model work better

• Ptolemy’s system had the planets spinning in large circles as they orbited earth.

• This system more accurately predicted the motion of the planets but was very complex.

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Aristarchus

• Greek Astronomer (310-230 BCE)

• First to suggest a Heliocentric model of the solar system.

• Few people believe in him as at the time they believed their Gods lived on Earth so it must be the center of the known Universe.

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Nicolaus Copernicus

• Polish Astronomer (1473-1543 BCE)• First astronomer to formulate a scientifically based

sun-centered model of the cosmos.• Delayed publishing his work until he was near

death, likely due to fear of condemnation from the Church.

• Nearly 60 years later the Church banned his book. It remained banned until 1835.

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Tycho Brahe

• Danish Nobleman (1546-1601)• Known for his accurate and complete astronomical and

planetary observations• Religious beliefs led Tycho to attempt to use his data to

blend Ptolemy and Copernicus’s views.• He believed the sun revolved around the earth and the

planets revolved around the sun.• The stars lay beyond all of this and also revolved around

earth.• His assistant, Johannes Kepler, would later develop his

own theory on the solar system.

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Johannes Kepler

• German mathematician and astronomer. (1571-1630)

• Used Brahe’s extensive observations to develop the most accurate model of the Universe based on his Three Laws of Planetary motion– 1. All planets move in ellipses with the sun at one

focus.– 2. A planet moves faster as it gets closer to the sun.– 3. The further a planet is from the sun, the slower it

revolves.

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Galileo Galilei

• Italian physicist, mathematician, astronomer, and philosopher (1564-1642)

• Was the first astronomer to use the telescope to make observations that helped to prove Copernicus and Kepler right.

• Found four of Jupiter’s Moons• Found objects outside of our solar system that did

not revolve around either the sun or earth.• Was sentenced to house arrest for his beliefs by

the Inquisition

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What is in our Solar System?

• 8 Planets• 166 known planetary moons• Billions of small bodies including

– 4 dwarf planets and their 4 moons– Asteroids– Meteoroids– Kuiper Belt objects– Comets– Interplanetary Dust

Types of Planets

• The planets are divided into 2 groups based on their location and composition

• Inner planets– Mercury, Venus, Earth, Mars– Small and Rocky with few moons

• Outer Planets– Jupiter, Saturn, Uranus, Neptune– Huge, gaseous, ringed, many moons

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NTK Terms

• Astronomical Unit - Distance from the earth to the sun (150,000,000 km) (AU)

• Revolution - A celestial body’s movement around another object, usually in an ellipse

• Rotation - The spinning of a celestial body like a top.

• Earth Day - the amt of time it takes earth to rotate once (24 hours)

• Earth Year- the amt of time it takes the earth to revolve once (365 days)

Mercury

• Closest planet to the sun.– 0.39 AU– The sun looks 3 times bigger

• Smallest planet in our solar system– About 40% the diameter of Earth

• Has no atmosphere– Is heavily cratered like the moon

Mercury

• Takes 88 Earth days to revolve around the sun

• 116 Earth days to rotate once

• Used to be larger, its liquid core shrunk as it solidified, leaving large cracks on the surface.

• Has no Moons

Mercury

• Temperature Range -168 ~ 427C

• Has polar ice caps

• Was named after the Roman winged messenger to the Gods as it is the fastest planet.

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Venus

• Second planet from the sun.– 0.72 AU

• Just slightly smaller than earth (5%)

• Has a very hot, dense, atmosphere that contains sulfuric acid clouds

• Sustains an average temperature of 450C likely due to runaway greenhouse gases.

Venus

• Revolves around sun in 225 Earth Days• Rotates very slowly, 243 Earth Days• Surface is protected by the thick atmosphere

from meteors so it looks much like Earth’s• No moons or ice caps• Named after the Roman goddess of Love• Brightest object in night sky aside from moon.

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Earth

• Third planet from the sun– 1 AU

• Largest of the Inner Planets (12,000km dia.)• Has an atmosphere containing mostly

nitrogen(78%) and oxygen (21%)• Temperature ranges from -88 to 58C• Earth is tilted from its axis of revolution by

23°

Earth

• Earth revolves around the sun in 365.24 Earth days.

• The Earth rotates in one Earth day or 23.93 hours.

• Has a molten core.• Has polar ice caps.• Has a moon (Luna or Moon)

– Roughly 25% the size of earth.

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Mars

• The fourth planet from the sun– 1.5 AU

• Roughly half the size of Earth• Has a very thin atmosphere composed mostly of

carbon dioxide• Temperature ranges from -140 to 20C• Called “Red Planet” due to iron oxide in the crust• Named after the Roman god of war.• Home to largest volcano in solar system, Olympus

Mons

Mars

• Mars revolves around the sun in 687 Earth Days.

• Mars’ rotation takes just slightly over one earth day (24.6 hours)

• Mars has polar ice caps made of dry ice.

• Mars has two tiny moons– Phobos(22km) and Deimos(13km)

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Jupiter

• 5th planet from the sun– 5.2 AU

• The largest of the planets (88,700km wide)• Is comprised almost entirely of hydrogen and helium. If

it were considerably larger, it could have become a star.• The gas is compressed to a liquid in the center.• There is likely a molten rocky core, possibly from

impacts with other objects.• Surface temp -153C (Core is hotter due to pressure from

gravity

Jupiter

• Jupiter takes about 12 years to revolve around the sun.

• Jupiter rotates in only 9.8 hours.• Jupiter has a giant storm on its surface called the

Great Red Spot• Jupiter has 63 named satellites

– Io and Europa are two well known moons

• Jupiter has rings, but they are very faint• Jupiter was named after the principle Roman God

(Greek equivalent Zeus)

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Saturn

• Saturn is the 6th planet from the sun– 9.5AU

• Second largest planet (75,000km wide)• Hydrogen and Helium with a liquid center

and a molten rock core.• Has a surface temperature of -185C (Core

hotter due to pressure from gravity)

Saturn

• Revolution takes 29 Earth Years• Rotation takes 10.2 Hours• Saturn has beautiful rings composed mostly

of ice and dust.• Saturn has 60 identified moons (52 named)

– Titan is the largest moon

• Named after the Roman god of agriculture, who happened to be Jupiter’s father.

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Four of Saturn's moons: Dione, Titan, Prometheus (edge of rings), Telesto (top center)

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Uranus

• Uranus is the 7th planet from the sun– 19 AU

• Third largest planet (51,000km wide)• Composed of Hydrogen, Helium and

Methane (blue-green color)• Also likely to have liquid center with

molten rock core.• Surface temperature of -114C

Uranus

• It takes 84 Earth years to revolve around the sun.• Rotates in just 18 hours.• Has 11 rings that run up and down because Uranus

is tilted nearly 90°• Has 27 known moons

– Titania is the largest

• Was named after the greek god of the sky. (Saturn’s Father)

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Neptune

• Neptune is the eighth and farthest planet from the sun -30 AU

• Neptune is nearly equal in size to Uranus– 50,000 km wide.

• Composed of hydrogen, helium, and methane (blue-green color)

• Also has liquid center and molten rocky core• Surface temperature of -125C

Neptune

• It takes Neptune 165 Earth years to orbit the sun.

• It takes only 19 hours to rotate

• Has several faint rings

• Named after the Greek god of the sea.

• Has 13 known moons– Triton is the largest.

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What else is in our solar system?

• Asteroids

• Meteoroids

• Kuiper Belt Objects

• Comets.

Asteroids

• Asteroids are large chunks of rock that orbit the sun

• Larger than a meteor(10m)

• Have no ice

• Most are located between the inner planets and outer planets in the Asteroid Belt

• Largest known is Ceres at 950km across

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Left to right: 4 Vesta, 1 Ceres, Earth's Moon

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Meteoroids

• Small sand to boulder sized debris in the solar system.

• Anything smaller is considered interplanetary dust.

• Tend to be debris from things like comets or collisions with planets.

• These meteoroids clump together as they orbit.

Meteors

• Meteors are meteoroids that enter Earth’s atmosphere.

• When earth passes through a clump of meteoroids, a meteor shower occurs.

• Meteor showers are regular and predictable.

• If the meteor hits the ground it is referred to as a meteorite.

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Kuiper Belt Objects

• Kuiper Belt is a region of space extending beyond Neptune. (30-55AU)

• Composed of small bodies of rock and ‘ice’• Very similar to comets, though without the

eccentric orbit.• Pluto is the most well known KBO• If we wanted to include Pluto as a planet we

would have to include the 70,000 other pluto-like objects in the Kuiper Belt.

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Comets

• Comets are small bodies in the solar system that orbit the sun. (100m to 40+km)

• As they approach the sun ice begins to sublimate, causing a visible coma and tail to form that points away from the sun.

• Comets have very elliptical orbits• As comets lose ice they also loose debris• Eventually they run out of ice and lose the coma and tail.• Comets all together form the Oort Cloud which is

estimated to end around 50,000 AU from the sun.

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