Chapter 16

Formation of the Solar System

Necessary Materials

Atoms, all of them, but

mostly hydrogen, are scattered throughout space. With little pressure, these atoms exist as gases (even though space is very cold). As pressure increases, heat increases and atoms can be forced to become liquids, then solids.

• Forces1. Gravity pulls on all

objects, drawing them closer together

2. Friction creates heat as atoms are forced into close contact

3. Pressure is created by particles bouncing off each other, pushing out.

Formation of the solar system

1. Gravity causes the atoms in the nebula to begin to collapse inward.

2. As matter falls in, friction between atoms creates heat. Collapsing matter also begins to spin (rotate).

3. Clumps begin to form (snow-ball effect) as particles collide. Clumps sweep up more matter, becoming larger.

- called planetessimals

4. The smaller clumps continue to orbit the center of gravity (the largest clump), now called a protostar.

5. At the center of gravity, the densest part of the cloud is also the hottest.

- Heat makes it start to glow (protostar).

6. At 10 million degrees celcius the cloud begins to fuse atoms ( a star turns on).

• Fusion- the process by which smaller atoms are fused into larger ones– Two hydrogen atoms get

squeezed together forming a helium atom.

– This releases a huge amount of energy.

5. At the center of gravity, the densest part of the cloud is also the hottest.

- Heat makes it start to glow.

6. At 10 million degrees celcius the cloud begins to fuse atoms ( a star turns on).

• Fusion- the process by which smaller atoms are fused into larger ones– Two hydrogen atoms get

squeezed together forming a helium atom.

– This releases a huge amount of energy.

7. The fusion process stops the collapse of the nebula as the protostar becomes a star. The flow of energy out from the star creates a solar wind, clearing out the loose gas and dust, leaving only the clumps that remain to become planets.

Stars verses Planets

• A star produces its own light and generates power by the process of fusion

• A planet cannot produce its own light (it shines only reflected light) and it orbits another object.

Planets are much smaller than stars. The main difference between them is their size. Bigger means hotter.

Mer

cury

Venus

Earth

Mar

s

Jupit

er

Satur

nUra

nus

Neptu

ne

Pluto

Sun

M V E M J S U N P

Structure of the Sun

• The sun is our local star which forms the heart of our solar system.

• It is a medium sized, medium-bright yellow star.

Core

Core- hottest, densest part of the sun, where fusion occurs

Radiative Zone

Radiative Zone- heat and light slowly work their way out

Convective Zone

Convective Zone- heat and light make their way out as hot gases rise and cooler gases fall

Photosphere- the visible surface of the sun

Chromosphere- lower atmosphere of the sun, can only be seen during a solar eclipse.

Corona- upper atmosphere of the sun, only visible during an eclipse.

Other parts of the sun

• Solar flares- eruptions or storms on the surface of the sun.

• Sun spots- cooler, dark spots on the sun– caused by disturbances in

the sun’s magnetic field.– Follows an eleven year

cycle. More sunspots mean higher average temperatures on Earth.

• Aurora- an Earth phenomena caused by solar particles colliding with the Earth’s magnetic field. (also called the Northern/ Southern Lights)

The Inner Planets

• Mercury• Venus• Earth• Mars

• Terrestrial– Rocky surfaces

MercuryFastest Planet

• Rotation– 58 days, 16 hours

• Revolution– 88 days

• Diameter– 4,878 km (smaller than

the Earth)

• Surface details– Looks a lot like our moon– No moons orbiting– No atmosphere– Very hot during the day,

very cold at night– Hard to study because it is

so close to the sun. It has been visited by one Earth satellite in the 1970’s. A new satellite is currently on its way to orbit the planet in 2011.

VenusEarth’s Twin

• Rotation– 243 days – Retrograde (sun rises

in the west)

• Revolution– 224 days

• Diameter– 12,104 km (only 12,104 km (only

slightly smaller than slightly smaller than the Earth)the Earth)

• Surface details– No moons orbiting– Dense atmosphere

keeps it very hot day and night.

• High winds, sulfuric acid rain

– It has been visited by several Earth satellites and landers.

• Radar maps show surface details similar to the Earth without water

Earth• Rotation

– 23 hours, 56 minutes

• Revolution– 365 days, 6 hours

• Diameter– 12,756 km

• Surface details– One moon, Luna– Complex atmosphere

keeps it from getting too hot during the day or too cool at night.

• Large amount of liquid water

– Only place in the universe known that is capable of sustaining life

MarsThe Red Planet

• Rotation– 24 hours, 37 minutes

• Revolution1 year, 322 days

• Diameter– 6,794 km (about 1/3 the

size of the Earth)

• Surface details– 2 moons, Phobos, Deimos

• Small moons, probably captured asteroids

– Thin atmosphere• Large dust storms and other

weather patterns seen

– It has been visited by several Earth satellites and landers.

• Detailed photos show surface details similar to the Earth with evidence of past water

The Asteroid BeltThe Planet that never was

• Around 2,000 asteroids have been discovered orbiting the sun between Mars and Jupiter. Most are small only a few miles across. There may be 1 million such objects orbiting inside this area.

The asteroid belt is found between the orbits of Mars and Jupiter. It holds most of the asteroids found orbiting the sun. It is believed they might have been a small planet that was prevented from forming by the gravity of Jupiter.

The first 4 asteroids discovered• Ceres (also the largest)

– Discovered 1/1/1801 by Giuseppe Piazzi– 1/3 the mass of all asteroids combined

• Pallas – Discovered 3/28/1802 by Heinrich Olbers– 1/12 the mass of all asteroids combined

• Juno – 9/1/1804 by Karl Harding– 1/100 the mass of all asteroids

• Vesta– Discovered 3/29/1807 (Olbers)– 1/10th the mass of all asteroids

The Outer Planets

• Jupiter• Saturn• Uranus• Neptune

• Gas Giants (no rocky surfaces)– Consist of layers of

gases that blend smoothly into the denser layers in their interiors

– All have systems of rings (made up of dust and small rocks)

– All have manyhave many moons

JupiterKing of the Planets

• RotationRotation– 9 hours, 50 minutes9 hours, 50 minutes

• RevolutionRevolution– 11.3 years11.3 years

• DiameterDiameter– 142,984 km 142,984 km (largest of

all planets, heavier than all of the planets together)

• Jupiter’s gravity makes it very important to the solar system.

• Surface detailsSurface details– 60-100 moons60-100 moons

• 4 very large moons, the rest 4 very large moons, the rest are very smallare very small

– Gases are divided into Gases are divided into bands of different colors, bands of different colors, altitudes and temperaturesaltitudes and temperatures

• Great red spot, a storm first Great red spot, a storm first seen over 400 years agoseen over 400 years ago

– Very thin ring system.Very thin ring system.– It has been visited by It has been visited by

several Earth satellitesseveral Earth satellites

SaturnPlanet with Ears

• Rotation– 10 hours, 20 minutes

• Revolution– 29.5 years

• Diameter– 120,536 km (least dense

planet, less dense than water)

• Saturn bulges at the equator because of its fast rotation and low density.

• Surface details– 40 - 60 moons

• The solar system’s largest moon, Titan, has its own atmosphere

– Gases are divided into bands similar but cooler than Jupiter’s

• Storms and aurora have been seen

– Only ring system easily seen on Earth.

– It has been visited by several Earth satellites, including one orbiting now

UranusA Planet on its Side

• Rotation– 17 hours, 14 minutes

• Revolution– 83.6 years

• Diameter– 51,118 km

• Surface details– 20-30 moons

- Some show evidence of violent pasts, which might explain why Uranus orbits sideways

– Less banding in the clouds (much cooler) than Jupiter or Saturn

– Planet orbits on its side• Each of its poles points at the sun for

part of the year

– It has been visited by one Earth satellite, Voyager 2

– First planet to be “discovered” (the closer ones can be seen by everyone)

• Found by William Herschel in 1781.

NeptuneOcean Planet

• Rotation– 16 hours, 7 minutes

• Revolution– 163.6 years

• Diameter– 49,528 km

• Surface details– 13+ moons

• One large moon, Triton, has a thin atmosphere

– Seems to give off more heat and light than it gets from the sun

• Great Dark Spot has been seen until recently

– It has been visited by one Earth satellite, Voyager 2

– Second planet “discovered”• Found by in 1846 John Adams

and Urbain Le Verrier, who predicted its location using Kepler’s and Newton’s laws.

The Edge of the Solar SystemThe Kuiper Belt, home of the comets. This is a region outside Neptune’s orbit, on the edge of our solar system, that holds many icy objects which may collide and fall toward the sun and melt.

PlutoDouble Planet

• Rotation– 6 days, 10 hours

(retrograde)• Revolution

– 248 years– Actually closer to the sun

than Neptune for part of its orbit

• Diameter– 2,320 km (smaller than our

moon)

• Surface details– 1 confirmed moon, Charon

• Charon orbits locked in a very tight orbit

• May be at least two other moons recently found.

– Surface is likely mostly ice and dust

• Not terrestrial nor gas• Similar to the composition of a

comet• Very small, very far away, very

hard to study

– It has not been visited yet, one Earth satellite is on its way

– Discovered by Clyde Tombaugh in 1930

Beyond Pluto

• Sedna

Comets are dirty snowballs that melt as they fall toward the sun. The gas and dust left behind produce a tail that is always pushed away from the sun.

The most famous comet is named after Edmond Halley. He was the first person to realize that comets return in cycles. He realized a series of comets that had been seen many times since 240 B.C. was actually a single comet. In the 1700’s he correctly predicted the return of the comet that would bare his name. It returned as predicted 16 years after he died. Halley’s comet returns every 76 years.

Short period comets from the Kuiper Belt have defined orbits within our solar system and predictable returns.

Long period comets come from farther away (the Oort Cloud) and swing far away from the sun. They might never return.

Coma is the dust a

nd gas surrounding

the comet itself (

called the nucleus)

Ion tail

Dust tail

The tail consists of two parts. A dust tail made of pieces of the comet lit by sunlight and an ion tail made of charged particles created by passing through the solar wind. The tail is only visibleas the comet approaches the sun. It shrinks and disappears as the comet orbits away. Studying comets lets us see what the early solar system was like since the material in a comet has been frozen and unchanged since the formation of the solar system.

• No atmosphere (means no weather)

• Made of the same rocks as the Earth (probably a piece broken off from the Earth early in its history).

• This is the only place, other than Earth, where humans have walked.

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The Moon (Luna)• Rotation

– 27 days, 7.7 hours• Revolution

– 27 days, 7.7 hours

• Keeps the same side always facing the Earth

• Diameter– 3,476 km

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Phases of the Moon

New Moon

Waxing crescent

First Quarter

Waxing gibbous

Full moon

Waning gibbous

Third QuarterWaning

crescent

• A solar eclipse occurs when the moon blocks the sun creating a shadow for some observers on the Earth.

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Only visible to those in the right place at the right time, always during the day, always during a new moon (but not every new moon).

Eclipse

• A lunar eclipse occurs when the moon passes through the shadow created by the Earth. Some light is bent by the Earth’s atmosphere causing the moon to change colors.

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Visible to everyone who can see the moon, always at night (or near sunrise or sunset), always during a full moon (but not every full moon).

Our moon, Luna, was most likely formed from pieces blown off of the Earth by a massive collision. This is believed because of the size of the moon, the closeness of the it’s orbit as well as the composition of rocks being very similar to those found on Earth.

The dark patches are called maria (meaning “seas”) because they were believed to contain water. Now we know they are darker colored rocks, probably created when lava filled massive impact craters.

The brighter spots are smaller impact craters and rays produced by materials thrown out by meteor collisions.

The moons of Mars were named after the children of the Greek god of war, Mars.

• Phobos (Fear) orbits closer to its planet than any other moon in the solar system. It takes only 7 ½ hours to orbit Mars and has a diameter of 23 km.

• Deimos (Hate) takes 30 hours to orbit Mars and has a diameter of 12 km.

Ganymede is the largest of the four and the heaviest of all moons.

Europa is covered with a smooth ice surface. It may hide an ocean below.

Io is badly beaten by Jupiter’s magnetic field. It is the most volcanically active place in the solar system

Callisto has many impact craters and a two-tone surface (one half is much lighter than the other).

Galileo used the first telescope to discover these moons (the first moons seen besides our own). By watching these moons orbit their parent planet Galileo confirmed his belief that the planets moved around the sun, which was different than common belief.

Major Moons of Jupiter: The Galilean Satellites

Titan is the largest moon in the solar system. It has an atmosphere made of methane. It is the only moon we have landed on, besides our own, with a robot spacecraft.

Iapetus has two different colored sides and a 20 mile high ridge around its middle making it look like a walnut.

Dione is made mostly of water ice.

Tethys has strange deep ridges of ice.

Major Moons of Saturn