The Solar System

The So= lar System

The nebular theory of formation states that the solar system began = as a huge cloud of dust and gas called a nebula, which later condensed to form t= he sun and the planets.

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The nebu= la from which our solar system evolved was made mostly of hydrogen and helium gases. The planets are made o= f a variety of elements. About 5 billion years ago the nebula theory states a star exploded into a huge super nova causing heavy elements to stream into space and fall down on a nearby nebula helping to form the sun and planets as this gas cloud collapsed and gravitational forces pulled matter to the center of the nebula. The nebula flattened and the sun b= egan to take shape at the center. =

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Gravity = caused particles of dust and gas to gather and clump. Over long periods of time, the clu= mps became larger and larger taking the shape of the planets. The inner planets of Mercury, Venu= s, Earth, and mars became so hot the helium and hydrogen were boiled away leav= ing the metals and rocky materials. T= he outer planets of Jupiter, Saturn, Uranus, and Neptune were less affected by= the heat and kept the lightweight gases and grew to enormous sizes. Smaller clumps of matter formed ar= ound them and became satellites or moons. Asteroids formed between Mars and Jupiter. Farther out in space, near the edg= e of the solar system are other clumps of icy matter forming a huge cloud. =

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Astronom= ers understand huge distances in astronomical units or AU. One AU is Earth’s average di= stance from the sun which is 150,000,000 kilometers (93,000, 000 miles).

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History

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Ptolemy (Greek) put the Earth at the center of the universe in his theory with all objects orbiting around the Earth. Nicolaus Copernicus (Polish) put the planets revolving around the sun in orbits. Johannes Kepler (German) supported the ideas of Copernicus but = he believed the orbits to be elliptical. He could not explain why the planets stayed in orbit. Sir Isaac Newton (English) explained the orbit of planets using the law of inertia stating a planet’s motion around the sun is the result of two= factors: inertia and gravity. Another way to say that planets or= bit the sun is to say they revolve around the sun. Planets also rotate on an axis whi= ch is an imaginary line through the center of the planet.

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Mercury

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Mercury = is the planet closest to the sun. Me= rcury is 4.879 kilometers in diameter and 58,000,000 kilometers from the sun on average. At 48 Kilometers per second, one revolution around the sun is 88 days. Mercury rotates slowly making one Mercury day equal to 59 Earth days. The sun appears nine times larger.&= nbsp; Mercury has almost not atmosphere so there is no weather. Small amounts of sodium have been detected in the atmosphere. W= ithout weathering, Mercury has changed very little over the past few billion years. There are cliffs and p= lains formed from volcanoes billions of years ago. The days are hot (430⁰ = up to 900^o C) and nights are cold (-170⁰ C). Mercury has no moons.

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Distance= from the sun: 3.2 light minutes

Period of rotation: 58 days 16 hours

Period of revolution: 88 days

Diameter= : 4,879 km

Density:= 5.43 g/cm³

Surface temperature: -173 to 427^=
0 C

Surface gravity: 38% of Earth

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Mercury

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Venus

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Venus ha= s a similar diameter, mass, and density to Earth. Venus is 12,104 kilometers in diam= eter and 108,000,000 kilometers from the sun on average. One day on Venus is 243 Earth days= or 8 months. One revolution around= the sun on Venus is 224 Earth days or 7.5 months. A day on Venus is longer than a ye= ar on Venus. If the sun was seen, it would rise in the west and set in the east because Venus rotates east to we= st in a reverse motion called retrogr= ade rotation.

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Venus ha= s a thick cloud cover. The clouds= are made of sulfuric acid and carbon dioxide.&= nbsp; The sulfuric acid falls and evaporates in the air never reaching the ground. Surface temperature i= s 480⁰ C. The hostile atmosphere inc= luded lightning. No water has been = found on Venus. The atmospheric pre= ssure is 91 times greater than sea level on Earth. Deep canyons, craters and blue fla= t plains covered by lava flows exist along with highland areas and the remains of volcanoes along with rock similar rocky areas on Earth. The sun cannot be seen through the clouds. Maat Mons is the largest volcano on Venus. The carbon dioxide atmosphere of Venus traps heat causing a greenhouse effect making t= he dark side of Venus as hot as the bright side of 460⁰ C hot enoug= h to melt lead and up to 1000⁰C.&nb= sp; Venus has no moons. Ve= nus can be seen in the night sky as a bright object in the west after sunset an= d is called the “evening star”.

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Distance= from the sun: 6.0 light minutes

Period of rotation: 243 days retrograde rotation

Period of revolution: 224 days 17 hours=

Diameter= : 12,104 km

Density:= 5.24 g/cm³

Surface temperature: 464⁰ = C

Surface gravity: 91% of Earth

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Venus

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Earth

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Earth is= 12,756 kilometers in diameter and is 150,000,000 kilometers from the sun on average. Earth takes 36= 5.26 days to orbit around the sun in one complete revolution. Earth is tilted 23 ½ ^o= toward the sun creating seasons on Earth. The atmosphere extends 100 kilome= ters above the surface. 20% of the atmosphere is oxygen and the rest is nitrogen with a small amount of other gases. The atmosphere contains water vapor and clouds of water droplets.&= nbsp; 70% of the planet is covered in water. Earth consists of the crust, mantl= e, and the outer and inner core.

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Distance= from the sun: 8.3 light minutes

Period of rotation: 23 hours 56 minutes=

Period of revolution: 365 days 6 hours<= o:p>

Diameter= : 12,756 km

Density:= 5.52 g/cm³

Surface temperature: -13 to 37^0<=
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C

Surface gravity: 100% of Earth

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Mother Earth

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Earth’s moon is 3476 kilometers is diameter. It is much less dense than Earth.<= span style=3D'mso-spacerun:yes'> The gravitational force of the moo= n is 1/6 of Earth. The average dis= tance to the moon is 384,403 kilometers. The circumference of the moon is about 10,927 kilometers. The moon rotates in 29 days, 12 ho= urs, and 43 minutes. The moon revo= lves around the Earth in 29 days, 12 hours, and 44 minutes. The length of day and night on the= moon is about 144 Earth days each. The mass of the moon is 1/8 of Earth’s mass and the volume of the moon is 1/50 of Earth’s volume. Moon rock is 4.6 billion years old. It seems the Earth and the moon formed at the same time.

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The moon= as no atmosphere and therefore has no weather.&n= bsp; Noon temperatures reach 100⁰ C and as low as -175^{0
C at night. The moon is dry w=
ithout
air and barren. There are mou=
ntains
thousands of meters high and highl=
ands
up to 8 kilometers above the plains.
The plains are called Maria=
(Mare
singular). The moon has m=
any craters. The moon had active volcanoes.}

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The moon revolves around the Earth in an elliptical orbit. The perigee is the point of the moon’s orbit farthest from the Earth (400,000 kilometers). The same side of the moon is alway= s seen on Earth because the moon’s rotation time and revolution time are the same. The moon may have forme= d when a giant asteroid the size of Mars collided with Earth tearing a chunk of material from the planet. May= be the Pacific Ocean is the hole left after the asteroid tore the moon from the Earth.&nbs= p; Moon rock and Earth rock are similar.

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Period of rotation: 27 days 8 hours

Period of revolution: 27 days 8 hours

Diameter= : 3,476 km

Density:= 3.34 g/cm³

Surface temperature: -170 to 134^=
0 C

Surface gravity: 17% of Earth

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Earth’s Moon

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Mars

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Mars app= ears a reddish color. Mars is 6,794 = kilometers in diameter and 228,000,000 kilometers from the sun on average. Mars make a complete rotation in 1= .03 Earth days and one complete revolution around the sun in 1.9 Earth years.

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Mars has= two small moons that orbit, and they are named Phobos (27 km diameter) and Deim= os (15 km diameter) after the Greek words for fear and terror. These moons are smaller that Earth’s moon and also cratered. Phobos is close to Mars and is slowly spiraling down and may smash i= nto Mars in about 40 million years.

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Mars soi= l is similar to Earth. The red col= or is due to iron oxide. Mars has volcanoes that were once active. The largest volcano on Mars is Olympus = Mons. It is wider than Hawaii and is three times higher than Mount Everest. Frozen water can be found in the northern icecap. The southern icecap is frozen carbon dioxide. The atmosphere on Mars is very thin having only 1% the pressure of Earth’s atmosphere, and the atmosphere of mars is made of carbon diox= ide (95%) making it very cold on the planet being well below 0^o C. The axis is Mars is tilted 25^=
0 causing seasons on Mars. Ther= e are winds up to 200 kilometers per hour creating large dust storms. The Valles Marineris canyon on mars is 240 kilometers wide at one point and 6.5 kilometers deep. On Earth thi= s size would stretch from New York to California. The axis is Mars is tilted causing seasons on Mars.

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Two expl= oration rovers (Opportunity and Spirit) were sen= t to Mars to explore the surface and test for water.

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Distance= from the sun: 12.7 light minutes

Period of rotation: 24 hours 37 minutes=

Period of revolution: 1 year 322 days

Diameter= : 6,794 km

Density:= 3.93 g/cm³

Surface temperature: -123 to 37⁰⁼ C

Surface gravity: 38% of Earth

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M= ars

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The Asteroid Belt

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Asteroid= s are made of rocks, metal or a combination of both. They are small and irregular, but = some are large such as Ceres with a diameter of 1000 kilometers. The diameter of our moon is 3400 k= ilometers. Asteroids sometimes speed through = space and collide with the planets. Impact scares are identified on Earth. One theory states that a giant ast= eroid collided with Earth 65 million years ago near the Yucatan Peninsula of Mexi= co causing the great extinction of the dinosaurs and 90 percent of the life fo= rms on Earth. <= /p>

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Some ast= eroids are named such as Ceres (940 km), Pallas (522 km), Juno, Hygiea (430 km) and Vesta (530 km). Others are Id= a, Gaspra and Eros. <= /span>

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On Febru= ary 12, 2001, NEAR (the Near Earth Aste= roid Rendezvous spacecraft) ended its one year mission by becoming the first spacecraft to land softly on an asteroid after going into orbit around the asteroid Eros on February 14, 2000.

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Eros close up

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Jupiter

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Jupiter = is big and bright in the night sky. Jupiter is 143,000 kilometers in diameter and 779,000,000 kilometers from the sun. One complete revolution around the sun takes 12 Earth years and one complete rotation ta= kes .41 Earth days. It is made mo= stly of hydrogen and helium gases like the sun and stars. The gas giants have so much mass, = they exert a much stronger gravitational force than the rocky planets. This gravity keeps the gases form escaping. The core of Jupiter= may reach 30,0000^o C which is almost five times the surface temperat= ure of the sun, but the upper could temperature is cold.

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The thic= k bands of atmospheric clouds that appear as bands of color are made mostly of hydr= ogen and helium gas along with some ammonia and methane. Huge storms swirls around the planet. The Great Red Spot is probably a hurricane that has been active for more than 300 years. The clouds become thicker and dens= er as they get closer to the center of the planet where the clouds may change into giant oceans of liquid hydrogen. This thick cloud cover produces an enormous atmospheric pressure. This pressure makes liquid hydroge= n act like a metal layer giving Jupiter a gigantic magnetic field called the magnetosphere. The core maybe= made of rock, ice, frozen carbon dioxide, and other compounds. Jupiter gives off more heat than it receives from the sun. There = are bolts of lightning in the atmosphere.

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Jupiter = has four moons known as the largest called the Galilean satellites among it total 63 plus moons. Io is the inner most moon with a = high sulfur content on the surface it appears brilliant orange yellow and has volcanoes. Europa is the next. Europa is ice covered and smaller than Io. It appears bright white. After Europa is Ganymede the largest moon of Jupiter. It is larger than the planet Mercury. It is made of rock and water ice. Then there is Callisto which is hea= vily cratered made of rock and ice.

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Distance= from the sun: 43.3 light minutes

Period of rotation: 9 hours 56 minutes<= o:p>

Period of revolution: 11 years 313 days=

Diameter= : 142,984 km

Density:= 1.33 g/cm³

Temperat= ure: -153⁰ C

Surface gravity: 236% of Earth

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   Jupiter

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Saturn

Saturn h= as magnificent rings that were discovered by Galileo. Saturn is 120,500 kilometers in di= ameter and 1,434,000,000 kilometers from the sun on average. One complete rotation is .45 Earth= days and one complete revolution around the sun is 29 Earth years.

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The ring= s are made of icy particles from microscopic to 100 kilometers is diameter. The outer edge of the most distant= ring is about 300,000 kilometers from Saturn.&n= bsp;

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Saturn s= pins rapidly on its axis which flattens the poles and bulges the equator. Saturn is made of mostly hydrogen = and helium gases. Wind speed at t= he equator reach 1800 kilometers per hour creating violent long storms with lightning. The clouds on Satu= rn form bands as on Jupiter. Sat= urn is colder than Jupiter. Saturn g= ives off three times more energy than it receives from the sun. Saturn has a huge magnetic field l= ike Jupiter. The density on Satur= n is very low and is the least dense planet in the solar system. Saturn would float in water.

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Saturn h= as 47 plus moons. The largest moon = is named Titan. Only Ganymede is larger. Titan has a nitrogen atmosphere wi= th methane, hydrogen cyanide, carbon monoxide, carbon dioxide and some other g= ases making Titan glow orange. This atmosphere is similar to Earth’s atmosphere before life formed. Other moons are Dione, Enceladus, = Rhea, Mimas, Iapetus, and Tethys.

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Distance= from the sun: 1.3 light hours=

Period of rotation: 10 hours 39 minutes=

Period of revolution: 29 years 155 days=

Diameter= : 120,536 km

Density:= .69 g/cm³

Temperat= ure: -185⁰ C

Surface = gravity: 92% of Earth

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Saturn

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Uranus

Sir Will= iam Herschel an English astronomer discovered Uranus in 1781. Uranus is 51,100 kilometers in dia= meter and 2,873,000,000 kilometers from the sun on average. Uranus is almost twice as far from= the sun as is Saturn. It is a gas= giant like Jupiter and Saturn.

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There is= a thick atmosphere of clouds made of hydrogen, helium and methane making the planet appear a greenish blue in color. The temperature may be as cold as -220⁰ C. Uranus is covered with super heated oceans of water, but the 11,000 kilometer atmosphere creates such atmospher= ic pressure, the water does not boil. <= /span>

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The axis= of Uranus is on its side tilted about 90⁰. Uranus is rotating from top to bot= tom instead of from side to side. as the other planets do. One complete rotation is .72 Earth= days and one complete revolution around the sun is 84 Earth years   Uranus also has rings that ar= e dark and may be made of methane ice and they circle the planet from top to bottom.

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Uranus h= as 27 plus moons including Miranda and Ariel.&nb= sp; These moons are active and the surfaces show fault lines.=

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Distance= from the sun: 3.7 light hours=

Period of rotation: 17 hours 14 minutes retrograde rotation

Period of revolution: 83 years 274 days=

Diameter= : 51,118 km

Density:= 1.27 g/cm³

Temperat= ure: -214⁰ C

Surface gravity: 89% of Earth

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   Uranus

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Neptune<= /st1:place>

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John Cou= ch an English astronomer in 1845 calculated where to find = Neptune. Jean Joseph Leverrier in France also calculated where to find Neptune. This information was ignored by most. Johann Galle took the information seriously and searched for this unknown object and found it. = Neptune is 49,500 kilometers in diameter and <= /o:p>

4,495,00= 0,000 kilometers from the sun on average. One complete rotation is .67 Earth days and one complete revolution around the sun is 164 Earth years. <= /span>Neptune and Uranus are about the same size, mass and temperature.

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Neptune is covered by thick cloud cover with a blue atmosphere. Giant methane clouds float in the = atmosphere of hydrogen and helium. The temperature at the top of the clouds may reach = -220^o C. The surface of Neptune may be an ocean of water and liquid methane over a rocky core. Neptune has rings made of dust particles.

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Neptune has 13 plus moons with Triton being the largest. Triton is the fourth largest moon in the solar system. It seems to be icy with frozen met= hane and an atmosphere. It orbits = Neptune backwards.

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Distance= from the sun: 4.2 light hours=

Period of rotation: 16 hours 17 minutes=

Period of revolution: 163 years 265 day= s

Diameter= : 49,528 km

Density:= 1.64 g/cm³

Temperat= ure: -225⁰ C

Surface gravity: 112% of Earth

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Neptune

Pluto

In 1930,= Clyde Tombaugh found this object named Pluto for the Roman god of the underworld. Pluto is 2,400 kilometers in diameter and 5,870,000,000 kilometers from the sun on average. One complete rotatio= n is 6.4 Earth days and one complete revolution around the sun is 248 Earth years. Pluto is moon size made mostly of various ices mostly methane.&nbs= p; Pluto has one moon named Ch= aron one half the size of the planet. Pluto may not be a planet but just the largest of thousands of objec= ts revolving around the sun out beyond Neptune.

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Distance= from the sun: 5.5 light hours=

Period of rotation: 6 days 9 hours retr= ograde rotation

Period of revolution: 248 years

Diameter= : 2,390 km

Density:= 2.05 g/cm³

Surface temperature: -236⁰= C

Surface gravity: 6% of Earth

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Pluto and moon

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Planet X= is a possibility as astronomers wonder what object may be pulling on the orbits = of Uranus and Neptune. Is it a planet? Is it a brown dwarf?<= span style=3D'mso-spacerun:yes'> Is it a black hole?

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Comets

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Beyond P= luto is the Oort cloud named for the Dutch astronomer Jan Oort. This is a vast collection of ice, = gas, and dust 15 trillion kilometers from the sun. From time to time, gravity from a = star will pull a dirty snowball called a comet out of the Oort and send it speed= ing toward the sun. As it moves t= oward the sun, ice, gas and dust heat up and form a could. The core is the nucleus. The 100,0= 00 or so comets in our solar system orbit the sun over and over again. Comets have very long and narrow elliptical orbits. There are = long period comets with long elliptical orbits and there are short period comets which return to the sun every few years.&n= bsp; A famous short comet is Halley’s Comet named after Edmund Hall= ey and English astronomer. This comet returns every 75 to 79 years. Halley should return around the year 2062. Another comet is the

Hale-Bopp that was seen in March and April 1997.

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The Kuiper belt is a doughnut shaped = region that extends from beyond Neptune’s= orbit to about 100 times Earth’s distance from the sun. The Oort cloud is a spherical region of comets that surrounds the solar system o= ut to more than 1000 times the distance between Pluto and the sun. Most comets come from these two re= gions.

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Meteoroids, Meteors,= and Meteorites

Meteoroids are chunks of metal or stone that = orbit around the sun. They come fro= m the asteroid belt or comets that have broken up. Millions fall through Earth’s atmosphere each day. Meteoroi= ds moving through the atmosphere are called meteors. The streak of light produced by the burning meteoroid is called a meteor. They are also called shooting stars. Most of them burn up in the atmosphere. They contain iron, nickel, and stone. A meteor t= hat strikes the Earth is called a mete= orite. Meteors create craters on Earth at impact. The most famous crate= r is the Barringer Meteorite Crater between Flagstaff and Winslow in Arizona.

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Meteorite

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Escape Velocity

The esca= pe velocity is the velocity a rocket must achieve to escape the gravitational pull. This depends on the mas= s of the planet and the distance of the rocket from the planet’s center.

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        Escape Velocities:

Object

Escape Velocity km/sec=

Mercur= y

4.2

Venus<= o:p>

10.3

Earth<= o:p>

11.2 (40,320km/hr)

Moon

2.3

Mars

5.0

Jupite= r

63.4

Saturn=

39.4

Uranus=

21.5

Neptune

24,2

Pluto<= o:p>

0.3 estimate

Sun

616

Sirius= B

3400 estimate

Neutro= n star

2000,000 estimate

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The Sun=

The sun&= #8217;s gravity is the most powerful force in the solar system holding all the plan= ets and comets in orbit. 99.8% of= the mass of the solar system is in the sun.&nb= sp; The sun has an interior and an atmosphere. The sun does not have a solid surf= ace like Earth as 75% of the sun is hydrogen and 25% is helium along with a sma= ll amount of other chemical elements. <= /span>

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The sun&= #8217;s interior consists of the core,= the radiation zone, and the convection zone. The sun’s energy comes from nuclear fusion in the core which is the process of hydrogen atoms joining t= o form helium under extreme high temperatures.&nb= sp; The core temperature of the sun reaches 15,000,000 degrees Celsius. = As hydrogen is changed to helium, some of the mass is converted to energy (lig= ht and heat). The light and heat= moves to the atmosphere of the sun and escapes into space to reach Earth as our m= ain source of energy. The radiation zone is the middle laye= r of the sun’s interior, and it is the region of very tightly packed gas w= here energy is transferred in the form of electromagnetic radiation. The convection zone is the outer most= layer of the sun’s interior. = Here hot gases rise from the bottom of the convection zone and gradually cool as they reach the top to then sink forming loops of gas that move energy toward the surface of the sun. The s= un is about 5 billion years old and has enough hydrogen fuel for another 10 billi= on years.

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The sun&= #8217;s atmosphere has three layers named the photosphere, the chromosphere, and the corona. The inner layer of the sun’s atmosphere is the phot= osphere. The photosphere is 400 kilometers = thick, and is 5000 to 8000⁰ C. The sunlight that reaches Earth comes from the photosphere. This is the light image of the sun= you see as you look at pictures of the sun.&nb= sp; You can not see the photosphere during a total eclipse. The chromosphere (the middle layer of the sun’s atmosphere) can be seen during a t= otal eclipse at the beginning and the end of the eclipse as the red glow just ar= ound the photosphere. The chromosp= here is 2000 to 3000 kilometers thick, and is 5000 to 10,000⁰ C. The corona can be seen during a total eclipse as the white halo around the sun. The corona is the outer layer of t= he sun’s atmosphere. The c= orona is millions of kilometers thick, and the temperature is over 1,000,000^=
0 C.

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A stream= of electrically charged particles leaving the corona is called solar wind. The magnetic field of the Earth bl= ocks these charged particles. Some particles enter the atmosphere at the north and south pole and interact with gas molecules in the atmosphere causing them to glow as sheets of light in = the sky called auroras.

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The sun&= #8217;s surface included sunspots, prominences, and solar flares. Sunspots are areas of gas in the photosphere that are cooler than the gases around them. The sunspots look dark because they are cooler than the gases around them. The number of sunspots varies ever= y 10 or 11 years. Prominences are huge looping eruptions of gas from the chromosphere. Red loops of gas (prominences) link sunspots in a group as sunspots usually occur in pairs or groups. The temperature of prominences reaches 10,000⁰ C.&= nbsp; When the loops between sunspots connect, they release large amounts = of energy that heats the gas on the sun to millions of degrees Celsius. The hydrogen gas then explodes out= into space and that explosion is called a solar flare. Solar flares incre= ase the solar winds which increase the charged particles reaching Earth’s atmosphere. These magnetic st= orms can disrupt radio, telephone, television signals and electrical power.

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Object	Escape Velocity km/sec=
Mercur= y	4.2
Venus<= o:p>	10.3
Earth<= o:p>	11.2 (40,320km/hr)
Moon	2.3
Mars	5.0
Jupite= r	63.4
Saturn=	39.4
Uranus=	21.5
Neptune	24,2
Pluto<= o:p>	0.3 estimate
Sun	616
Sirius= B	3400 estimate
Neutro= n star	2000,000 estimate