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The Solar System

• 1 star

• 8 planets

• several dwarf planets

• many moons

• asteroids, comets, meteoroids

SOLAR SYSTEM • Consists of the Sun and the

astronomical objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago.

Sun: 99.85%

Planets: 0.135%

Comets: 0.01%

Satellites: 0.00005%

Minor Planets: 0.0000002%

THEORIES ABOUT THE

ORIGIN OF THE SOLAR

SYSTEM

• Nebular Hypothesis/Theory

• Hydrogen and other gases swirled around and condensed into our Sun and its planets.

• Fission Theory

• One day, our Sun burst open, and planets and moons shot out at high speeds and went to their respective places, then stopped, and started orbiting the Sun, as the moons began orbiting the planets.

• Capture Theory

• Planets and moons were flying around, and some were captured by our Sun and began circling.

• Accretion Theory

• A pile of space dust and rock chunks pushed together into our planets, and other pile pushed itself into our moon. Then the moon got close enough and began encircling the Earth.

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• Planetary Collision Theory

• Our world collided with a small planet, and the explosion threw off rocks which became the moon, and then it began orbiting us.

• Stellar Collision Theory

• Our planets, moons and Suns spun off from the collision between stars.

• Gas cloud Theory

• Gas clouds were captured by our Sun. But instead of being drawn into it, they began whirling and pushing themselves into planets and moons.

Formation of the Solar System

Any theory to describe the formation of

our Solar System must be consistent

with these facts:

1. Each planet is isolated in space.

2. The orbits are nearly circular.

3. The orbits of the planets all lie in roughly the same plane

4. The direction the planets orbit around the Sun is the same

as the Sun’s rotation on its axis.

5. The direction most planets orbit on their axes is the same

as that for the Sun.

6. The direction of the planetary moon’s orbits is the same

as that of the planet’s rotation.

7. The terrestrial planets are very different from the Jovian

planets.

8. Asteroids are different from both types of planets.

9. Comets are icy fragments that don’t orbit in the ecliptic

plane.

ASTRONOMERS THAT

CONTRIBUTED TO

THE DEVELOPMENT

OF THE CONCEPT OF

THE SOLAR SYSTEM

CLAUDIUS PTOLEMY

• Proponent of the Geocentric model of the solar system, where the Earth is the center of the solar system and all other planets, along with the Sun, wanderers.

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NICOLAUS COPERNICUS (1473-1543)

• Concluded Earth is a planet

• Constructed a model of the solar system that put the Sun at the center, but used circular orbits for the planets.(Heliocentric model)

TYCHO BRAHE (1546-1601)

• Precise observer

• Tried to find stellar parallax- the apparent shift in a star’s position due to the revolution of Earth.

• Did not believe in the Copernican system because he was unable to observe stellar parallax.

JOHANNES KEPLER (1571-1630)

• Planets revolve around the Sun

• Three laws of planetary motion

• All orbits are Ellipses

• As a planet gets closer to the sun it speeds up, when it is farther away it slows down

• There is a relationship between the distance an object is from the sun and the time it takes to orbit.

1st Law 3rd Law 2nd Law

The laws of planetary motion were

determined by Johannes Kepler in

1609. The planets’ orbits obey

these three laws based on the

effects of gravity. The Sun’s

gravitational pull dominates the

motions of all planets.

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Sizes are determined from

angular size and distance

The distances to planets are known

from Kepler’s Laws

GALILEO GALILEI (1564-1642)

• Supported Copernican Theory

• Constructed an astronomical telescope in 1609

• Galileo made two major observations with his telescope:

• Observed the moon of Jupiter- showed that some object orbit something OTHER than the Earth, so why couldn't the Earth orbit something else?

• Observed the phases of Venus. IF Venus orbited around the Earth, there is no way that we would see phases. THE ONLY WAY we would see phases of Venus is if both planets (Venus AND Earth) orbited the Sun

The Sun

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Sun Fact Sheet The Sun is a normal G2 star, one of more than 100 billion stars in our galaxy. Diameter: 1,390,000 km (Earth 12,742 km or nearly 100 times smaller) Mass: 1.1989 x 1030 kg (333,000 times Earth’s mass) Temperature: 5800 K (surface) 15,600,000 K (core) The Sun contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest). Chemical composition: Hydrogen 92.1% Helium 7.8% Rest of the other 90 naturally occurring elements: 0.1%

The Sun and its Planets to Scale

Energy is created in the core when hydrogen is fused to helium. This

energy flows out from the core by radiation through the radiative

layer, by convection through the convective layer, and by radiation

from the surface of the photosphere, which is the portion of the Sun

we see.

The seasons occur because the tilt of the Earth's axis keeps a

constant orientation as the Earth revolves around the Sun. A.

Summer in northern hemisphere. B. Winter in southern

hemisphere

Sun does not rotate as a rigid sphere. The equator

of the Sun rotates faster than the poles of the Sun.

This is called the differential rotation. Sunspots

and many other solar activities are due to this

differential rotation.

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Sun’s Magnetic Field

The Sun's corona is threaded with a complex

network of magnetic fields. Solar storms and

flares result from changes in the structure and

connections of these fields.

When some of the Sun's magnetic field lines are filled

with hot gas, we see a magnetic loop.

Sunspots

Sunspots appear as dark spots on the surface of the Sun.

Temperatures in the dark centers of sunspots drop to

about 3700 K (compared to 5700 K for the surrounding

photosphere). They typically last for several days,

although very large ones may live for several weeks.

Spectrum analysis shows that sunspots have strong magnetic field, about 1000

times stronger than the Sun's average. Sunspots usually appear in pairs. The two

sunspots of a pair have different polarities, one would be a magnetic north and

the other is a magnetic south, and can be joined by magnetic field lines. The

strong magnetic field locks the gas of the photosphere in places and inhibits the

hotter gas below to rise at the sunspots. As a result, the sunspots are cooler.

Sunspots appear to coincide with changes in the climate of the Earth. Studies

show that during the last ice age, there were very few sunspots

Granules

Energy rises to the surface as gas wells up in the

cores of the granules, and cool gas sinks around their

edges.

Convection from inside the sun causes the

photosphere to be subdivided into 1000-

2000km cells.

Prominences are dense clouds of material

suspended above the surface of the Sun by

loops of magnetic field.

Solar Prominences Solar Flares

Images from SOHO*

*NASA/ESA Solar and Heliospheric Observatory

spacecraft

Solar flares are tremendous explosions on the

surface of the Sun. In a matter of just a few

minutes they heat material to many millions of

degrees and release as much energy as a billion

megatons of TNT. They occur near sunspots,

usually along the dividing line (neutral line)

between areas of oppositely directed magnetic

fields.

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Coronal Mass Ejections (CMEs)

Coronal mass ejections (CMEs) are huge

bubbles of gas threaded with magnetic field

lines that are ejected from the Sun over the

course of several hours.

Corona and Solar Wind

Solar wind is the continuous flow of charged particles

(ions, electrons, and neutrons) that comes from the Sun

in every direction.

The Sun’s Corona is forever expanding into

interplanetary space filling the solar system with

a constant flow of solar wind.

Solar wind shapes the Earth's magnetosphere and magnetic storms are

illustrated here as approaching Earth. These storms, which occur

frequently, can disrupt communications and navigational equipment,

damage satellites, and even cause blackouts. The white lines represent

the solar wind; the purple line is the bow shock line; and the blue lines

surrounding the Earth represent its protective magnetosphere.

Hertzsprung-Russell diagram of star luminosity versus surface

temperatures. The vertical axis is a comparative one based on the Sun

having a luminosity of 1. The horizontal axis is reversed from the

normal order, with values of surface temperature increasing to the left.

Note that the Sun is a middle-range, main-sequence star.

Due to the discovery of additional solar system

bodies in recent years, it became necessary to

re-examine the term “planet”. At the August

2006 International Astronomical Union meeting

in Prague, a new definition was passed.

RESOLUTION 5A:

(1) A planet is a celestial body that (a) orbits the Sun, (b)

has enough mass to form a spherical shape, and (c)

has cleared the neighborhood around its orbit.

(2) A dwarf planet is a celestial body that (a) orbits the

Sun, (b) has enough mass to form a spherical shape,

(c) has not cleared the neighborhood around its orbit,

and (d) is not a satellite.

Thus, Pluto is now a Dwarf Planet mainly

because it has not “cleared its neighborhood”

sufficiently. There are other objects in similar

orbits as Pluto - Neptune, Pluto’s moon Charon,

Kuiper Belt objects.

What is a Planet? Masses (and densities) - determined through

observing the gravitational effect of the

planet on some nearby object (moons,

nearby planets, satellites)

• Planets orbit the

sun counter-

clockwise as seen

from the North

Celestial Pole.

• All planets are

roughly in the same

orbital plane

EXCEPT Mercury

(and the dwarf

planet Pluto).

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Terrestrial Planets

•Mercury, Venus, Earth

and Mars

•Close to Sun

•Small masses, radii

•Rocky, solid surfaces

•High densities

•Slow rotation

•Weak magnetic field

•No rings

•Few moons

Jovian Planets

•Jupiter, Saturn, Uranus,

and Neptune

•Far from Sun

•Large masses and radii

•Gaseous surface

•Low densities

•Fast rotation

•Strong magnetic field

•Many rings

•Many moons

MERCURY

• Known as “the messenger”

• Closest planet to the Sun and thus

considered the innermost

• No atmosphere

• No moon

• Revolves quickly at about 88 Earth days

and rotates slowly at about 79 Earth

days

• Very cold planet at nighttime (-173 °C)

and the day time temperature is about

472 °C

MERCURY VENUS

• Brightest planet in the night sky

next to our moon and known as

the goddess of love and beauty.

• Usually called the twin planet

Earth which orbits the Sun in

about 225 Earth days.

• Hottest planet due to Green house

effect.

• No moon

VENUS EARTH

• Only Living planet in the solar system.

• Has one moon named Luna

• Revolves 365 ¼ days in the Sun and Rotates 24 hours

• Has a layer of atmosphere that regulates its surface temperature.

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EARTH AND MOON

MARS

• Known as the red planet and

named after the roman god of war

• Martian atmosphere has only about

1% of the Earth’s atmosphere the

rest compose of carbon dioxide.

• Has large volcano known as Mons

Olympus

• 2 moons name Phobos and Deimos

MARS WITH PHOBOS AND DEIMOS

JOVIAN PLANETS

• Large planets of the solar system.

• Called the outer planets since they reside on the farther part of the solar system.

• All of them have rings thought only the rings of Saturn are thick enough to be observed by the naked eye.

• Gaseous planets and have small densities

JUPITER

• Largest planet in the solar system

• Mainly made up of hydrogen-helium

• Has 63 moons

• The largest and most prominent are referred to as Galilean moons: Callisto, Ganymede, Europa and Io

• With great red spot

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SATURN

• Known as the most elegant planet because of its visible rings

• Circles the sun in about 29.46 Earth years

• The largest known moon is the Titan

• Has a density less than that of water

• Has 62 moons

URANUS

• Known as the sideways planet

because the planet rotates on

its side. Its axis of rotation is

parallel of its orbit.

• Has 27 moons

• Two largest moons are Titania

and Oberon discovered by

William Herchel in 1787.

NEPTUNE

• Outermost planet in the solar

system

• Also believed as the twin of

Uranus

• Discovered in September 23, 1846

by Johann Gottfried Galle and

Louis d’ Arrest.

• Methane is the main component of

its atmosphere which gives the

bluish-green color of the planet.

• Has 13 moons. Largest is the Triton

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WAY TO REMEMBER THE 8 PLANETS

My…………… Mercury

Very…………. Venus

Energetic…….. Earth

Mother………. Mars

Just………….. Jupiter

Served………. Saturn

Us…………… Uranus

Nachos……… Neptune

DWARF PLANETS

According to the International Astronomical

Union (IAU), which sets definitions for

planetary science, a dwarf planet is a

celestial body that:

• Orbits the Sun.

• Has enough mass to assume a nearly

round shape.

• Has not cleared the neighborhood

around its orbit.

• Is not a moon.

PLUTO

• Discovered in 1930.

• Has 3 moons: Charon, Hydra and

Nix.

• Two-thirds the diameter of Earth's

Moon and probably has a rocky core

surrounded by a mantle of water ice.

• More exotic ices like methane and

nitrogen frost coat its surface.

ERIS

• Takes icy Eris 557 Earth years to

complete a single orbit around our

Sun.

• Has 1 moon named Dysnomia

• Eris, like Pluto, is still smaller than

Earth's Moon.

• The thin atmosphere will thaw in

hundreds of years as it gets closer to

the Sun, revealing a rocky surface

scientists believe is similar to Pluto.

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HAUMEA

• One of the fastest rotating large objects in our

solar system.

• It completes a turn on its axis every four hours.

• It takes 285 Earth years for Haumea to make

one orbit around our sun.

• Haumea's known moons are Hi'aka and

Namaka.

• Astronomers believe Haumea is a made of rock

with a coating of ice.

• Discovered in March 2003 at the Sierra Nevada

Observatory in Spain.

MAKEMAKE

• It takes 310 Earth years for this dwarf planet to

make one orbit around our Sun.

• Astronomers found signs of frozen nitrogen on

Makemake's surface.

• Frozen ethane and methane have also been

detected on the surface.

• Its unofficial codename was Easterbunny. It was

officially recognized as a dwarf planet by the

International Astronomical Union in 2008.

CERES

• Ceres ended up among the leftover debris of

planetary formation in the main asteroid

belt between Mars and Jupiter.

• Ceres is approximately 580 miles (930

kilometers) across, about the size of Texas.

• Ceres were composed of 25 percent water, it

may have more water than all the fresh

water on Earth.

• Ceres was the first object discovered in the

asteroid belt. Sicilian astronomer Father

Giuseppe Piazzi spotted the object in 1801.

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SEDNA

• Discovered in 2003 and also known as 2003 VB12, is most likely a dwarf planet.

• Sedna does have a highly elliptical orbit, which means that it ranges from 76 AU to 975 AU.

• Some astronomers calculate the orbital period as more than 12,000 years long.

QUAOAR

• Quaoar is a newly discovered Kuiper

Belt object, found in June 2002 by Chad

Trujillo and Mike Brown at Caltech in

Pasadena.

• It's the largest Kuiper Belt object

currently known, half the diameter of

Pluto (about 1/8 the volume), and 1.6

billion kilometers (1 billion miles)

further away than Pluto.

• Quaoar is about 1250 km in diameter,

roughly the size of Pluto's moon

Charon.

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Comets

Dirty snowballs - dust and rock in

methane, ammonia and ice

All light is reflected from the Sun - the

comet makes no light of its own

The nucleus is a few km in diameter

•Long period comets take up to 1 million

years to orbit the Sun (may originate in

the Oort cloud)

•Short period comets orbit the Sun in 200

years or less (e.g. Halley’s comet) –

likely originate in the Kuiper belt and were

kicked into an eccentric orbit

Comet Temple 1 image obtained from Stardust satellite

flyby on Feb 14, 2011

•Crater with a

small mound in the

center indicates

cometary nucleus

is fragile and weak.

•Caused by

impactor from

Deep Impact

mission in 2005 –

found comet to be

less icy and more

dusty than

expected...

Meteoroids – interplanetary

rocky objects smaller than

100m (down to grain size).

Consist mainly of iron and

nickel with some carbon

• called a meteor as it burns in

the Earth’s atmosphere

• if it makes it to the ground, it

is a meteorite

Old objects that appear to be

as old as the solar system

based on carbon dating

Most meteor showers are

the result of the Earth

passing through the orbit of

a comet which has left

debris along its path

Spring Meteor

showers:

Lyrids – Apr 21/22

Eta Aquarids – May 5/6

Asteroids - rocks with sizes greater

than 100m across

Most asteroids remain in the Asteroid belt

between Mars and Jupiter but about 2000

have orbits that cross Earth’s path.

Based on known

Earth-crossing

asteroid orbits, it is

estimated that 3

asteroids impact

Earth every 1

million years!

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Asteroid 2005 YU55 to Approach Earth on

November 8, 2011

Near-Earth asteroid 2005 YU55 (about 400m in

size) will pass within 0.85 lunar distances from the

Earth on November 8, 2011.

Asteroids range in size from 100m

to ~1000km

They are composed of

carbon or iron and other

rocky material.

The Asteroid belt is a group of

rocks that appear to have

never joined to make a planet

(as opposed to having once

been a planet that was later

destroyed).

•Too little mass •Different chemical compositions •Planet formation probably effected by nearby Jupiter’s strong gravity