THE SOLAR SYSTEM

OUR SOLAR SYSTEM IS THOUGHT TO BE 4.5 BILLION YEARS OLD. IT WAS FORMED FROM A NEBULA CONTAINING MATERIAL THAT HAD BEEN THROUGH 2 PREVIOUS SUPER NOVAE. 99.9% OF THE MASS OF THE SOLAR SYSTEM IS FOUND IN THE SUN. THE MOON WAS FORMED SHORTLY AFTER EARTH WHEN A MARS SIZED PLANET COLLIDED WITH EARTH.

UNITS OF MEASURMENT IN ASTRONOMY ASTRONOMICAL UNIT, AU = 93,000,000 MILES = 150,000,000 km = AVERAGE DISTANCE FROM EARTH TO THE SUN LIGHT YEAR = 5.9 X MILES = 9.5 X km = THE DISTANCE LIGHT TRAVELS IN ONE YEAR Speed of light = 186,000 mi/sec = 3 x 10 8 meters/sec

OUR SOLAR SYSTEM CONSISTS OF: AN AVERAGE STAR, OUR SUN 8 PLANETS (not counting Pluto) THE ASTEROID BELT – BETWEEN MARS AND JUPITER THE KUIPER BELT – WHERE PLUTO AND A NUMBER OF OTHER PLANETESIMALS ARE LOCATED THE OORT CLOUD – FURTHEREST REACHES

THE PLANETS ARE (in order) MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, URANUS, AND NEPTUNE. THEY ALL ORBIT THE SUN IN APPROXIMATELY THE SAME PLANE - THE ECLIPTIC.

PlanetDistance x 10 6 km Distance in AU Period to Revolve Around Sun Mercury days Venus days Earth days Mars days Jupiter yrs Saturn yrs Uranus yrs Neptune yrs

The terrestrial planets - mercury, venus, earth, and mars - sometimes referred to as the rocky planets.

MERCURY Diameter – 3031 miles (38% of Earth’s) Mass – 5.5% of Earth’s Distance from sun – from 28 million miles to 43 million miles Surface gravity – 38% of Earth’s Average surface temperature – 800 o F Atmosphere – none Satellites – none Sunlight – 1000% of Earth’s

MERCURY Rotates in earth days – orbits in earth days.

VENUS Diameter – 7521 miles (94.8% of Earth’s) Mass – 95% of Earth’s Surface gravity – 90% of Earth’s Average surface temperature – 900 o F Distance from sun – approx. 67,000,000 mi. Sunlight – 190% of Earth’s Atmosphere – 96% carbon dioxide, 3.2% nitrogen and 0.8% other Satellites - none

VENUS Rotates in 243 days – orbits 225 days.

EARTH Diameter – 7926 miles Mass – 1.3 x pounds Distance from sun – approx. 93,000,000 miles Average surface temperature – 56 o F Number of satellites – 1 Atmosphere – 78% nitrogen, 21% oxygen, 0.9% argon, 0.1% other

EARTH Rotates in 23 hours, 56 min – orbits in days.

IT IS A LONELY PLACE. THE NEAREST STAR IS 4.22 LIGHT YEARS AWAY. THE OTHER PLANETS IN OUR SOLAR SYSTEM ARE NOT CAPABLE OF SUPPORTING LIFE AS WE KNOW IT. VENUS HAS AN ATMOSPHERE OF MOSTLY CARBON DIOXIDE AND A SURFACE TEMPERATURE OF 472 o K. MARS HAS A VERY THIN ATMOSPHERE OF MOSTLY CARBON DIOXIDE AND A SURFACE TEMPERATURE OF -140 o TO 20 o C.

MARS Diameter – 4221 miles ( 53.2% of Earth’s) Mass – 11% of Earth’s Distance from sun – from 128 million miles to 155 million miles Sunlight – 36 – 52% of Earth’s Surface gravity – 38% of Earth’s Average surface temperature o F Satellites – 2 Atmosphere – 95% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.7% other

MARS Rotates in 24 hours, 37 min – orbits in 687 days.

MERCURYVENUSEARTHMARS DIAMETER3031 mi7512 mi7926 mi4221 mi MASS5% of Earth 95% of Earth 1.3 x pounds 11% of Earth AV. TEMP.800 o F900 o F56 o F- 20 o F ATMOSPH ERE Very thin96% CO 2 Dense* 79% N 2 20% O 2 95% CO 2 2.7% N 2 ROTATION58 days243 days24 hrs ORBIT88 days225 days365 days687 days * Surface pressure on Venus is 90 atmospheres.

ASTEROID BELT EXTENDS FROM 2.15 au TO 3.3 au. THE INNER ASTEROIDS ORBIT THE SUN IN APPROX 3 YEARS, WHILE THE OUTER ASTEROIDS TAKE APPROX. 6 YEARS. THERE IS NO RELIABLE ESTIMATE OF THE NUMBER OF ASTEROIDS. THE TOTAL MASS IS THOUGHT TO BE AROUND 1/20 th OF THE MASS OF OUR MOON. THE LARGEST ASTEROID IS CERES, WHICH IS 650 MILES ACROSS. MOST ARE LESS THAN 30 FEET.

JUPITER DISTANCE FROM SUN = 5.2 AU MASS = 318 X EARTH DIAMETER = 11 X EARTH ATMOSPHERE = HYDROGEN AND HELIUM SURFACE = LIQUID HYDROGEN ORBIT = 12 YEARS ROTATION = 10 HOURS MOONS = 63 (4 GALILEAN MOONS)

ONE OBVIOUS FEATURE IS THE GREAT RED SPOT, WHICH IS LARGE ENOUGH TO PUT TWO EARTHS IN SIDE-BY-SIDE. IT IS A LARGE STORM, AND IT HAS LASTED FOR OVER 300 YEARS.

Io, Europa, Ganymede, and Callisto

TIDAL FORCES HEAT THE INTERIOR OF THE TWO INNERMOST MOONS. IO HAS TREMENDOUS VOLCANIC ERUPTIONS. IO IS 2% LARGER THAN EARTH’S MOON. EUROPA HAS A SHELL OF WATER ICE, WHICH IS ESTIMATED TO BE BETWEEN 12 AND 90 mi THICK. EUROPA IS ABOUT 12% SMALLER THAN EARTH’S MOON.

CASTILLO AND GANYMEDE ARE BOTH SLIGHTLY LARGER THAN THE PLANET MERCURY. BOTH MAY HAVE LIQUID OCEANS DEEP BENEATH THEIR ICY CRUSTS. JUPITER MAY HAVE A ROCKY IRON/NICKEL CORE 1.5 TIMES EARTH’S DIAMETER. DUE TO THE EXTREME GRAVITY, THE CORE TEMPERATURE MAY BE AS HIGH AS 20,000 o C.

SATURN DISTANCE FROM SUN = 9.5 AU DIAMETER = 9.4 EARTH MASS = 95 X EARTH ORBIT = 29.5 YEARS ROTATION = 11 HOURS

THOUGHT THAT SATURN HAS A CORE APPROX. 2.5 TIMES EARTH’S DIAMETER, 20 TIMES EARTH’S MASS, AND 15% OF JUPITER’S TOTAL MASS. THE PLANET IS MADE MOSTLY OF MOLECULAR HYGROGEN (88%) AND HELIUM (11%). SATURN’S RINGS ARE VERY THIN. THEY ARE 250,000 km ACROSS, BUT THEY ARE ONLY 1 km THICK. THERE IS NOT MUCH MATERIAL THERE. IF IT WERE ALL COMPRESSED INTO A SINGLE OBJECT, IT WOULD ONLY BE 100 km THICK.

LIKE JUPITER, SATURN RADIATES MORE ENERGY THAN IT RECEIVES FROM THE SUN. ALSO, LIKE JUPITER, SATURN HAS A STRONG MAGNETIC FIELD. SCIENTISTS THINK THIS IS CAUSED BY THE METALLIC HYDROGEN IN THE INTERIOR.

TITAN IS THE LARGEST MOON OF SATURN. IT HAS AN ATMOSPHERE COMPOSED MOSTLY OF NITROGEN AND METHANE. THE ATMOSPHERIC PRESSURE AT THE SURFACE IS 1.6 TIMES THAT OF EARTH.

THE SURFACE OF TITAN IS COVERED WITH HYDROCARBON LAKES, PRIMARILY METHANE AND ETHANE. PICTURE OF TITAN SHOWING ITS ATMOSPHERE.

SATURN WAS THE FURTHEREST PLANET FROM THE SUN KNOWN TO THE ANCIENTS. URANUS WAS NOT DISCOVERED UNTIL 1781 BY WILLIAM HERSCHEL USING A TELESCOPE.

URANUS DIAMETER = 4 X EARTH MASS = 11 X EARTH DISTANCE FROM SUN = 19.2 AU ROTATION = 17 HOURS ORBIT = 84 YEARS THE ROTATIONAL AXIS IS ONLY 8 DEGREES OUT OF THE PLANE OF THE ORBIT, SO WE SEE IT ON ITS SIDE. COMPOSITION = MOSTLY HYDROGEN AND HELIUM. MOONS = 5 LARGE AND 10 SMALL

THE BLUE COLOR IS DUE TO METHANE IN THE ATMOSPHERE. URANUS HAS A MAGNETIC FIELD ABOUT 50 TIMES STRONGER THAN THAT OF EARTH. IT DOES NOT HAVE AURORA LIKE JUPITER AND SATURN AS IT IS FURTHER FROM THE SUN. URANUS HAS SOME NARROW RINGS – PROBABLY ROCKY COMPOSITION.

NEPTUNE NEPTUNE IS SLIGHTLY SMALLER IN DIAMETER THAN URANUS, BUT HAS SLIGHTLY GREATER MASS. DISTANCE FROM SUN = 30 AU ROTATION = 16 HOURS ORBIT = 165 YEARS

NEPTUNE IS THOUGHT TO HAVE A ROCKY CORE ABOUT 15 TIMES AS MASSIVE AS EARTH. TILT ON AXIS = 50 degrees NEPTUNE HAS A MAGNETIC FIELD SLIGHTLY LESS THAN THAT OF URANUS.

NEPTUNE HAS FAINT RINGS. IT HAS 2 LARGE MOONS AND 6 SMALLER ONES. THE LARGEST IS TRITON AND IS ABOUT THE SAME SIZE AS OUR OWN MOON. TRITON HAS A THIN ATMOSPHERE OF MOSTLY NITROGEN AND POLAR ICE CAPS – ALSO NITROGEN.

PLUTO PLUTO IS 2/3 THE SIZE OF OUR OWN MOON AND 1,200 TIMES FURTHER AWAY. THIS MAKES IT VERY DIFFICULT TO SEE, EVEN WITH A TELESCOPE. DISTANCE FROM SUN = 40 AU ROTATION = 6 ½ DAYS ORBIT = 248 YEARS

PLANETDISTANCE FROM SUN MERCURY0.39 VENUS0.72 EARTH1 MARS1.5 JUPITER5.2 SATURN9.5 URANUS19.2 NEPTUNE30 PLUTO40

THERE IS A SCATTERED RING OF DEBRIS CONSISTING OF OBJECTS MADE MOSTLY OF ICES THAT EXTENDS FROM ABOUT 30 TO 50 AU. THIS REGION IS CALLED THE KUIPER BELT. SCIENTIST ESTIMATE THAT THERE MAY BE AS MANY AS 100,000 OBJECTS IN THE KUIPER BELT WITH DIAMETERS GREATER THAN 50 KM, BUT THE TOTAL DENSITY IS PROBABLY NOT GREATER THAN 1/10 THAT OF EARTH.

BEYOND THE KUIPER BELT, SCIENTIST BELIEVE THERE IS A SPHERICAL CLOUD OF DEBRIS KNOWN AS THE OORT CLOUD. THIS EXTENDS FROM ABOUT 50,000 TO 100,000 AU OR 1 LY TO ABOURT 1.7 LY FROM THE SUN. THIS REGION COULD CONTAIN UP TO 1 TRILLION ICY OBJECTS AND IS THOUGHT TO BE THE ORIGIN OF MOST COMETS.

The Sun's nearest known stellar neighbor is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away. Our solar system is part of our home galaxy. Our home galaxy is the Milky Way galaxy, a spiral galaxy of approximately 200 billion stars.

Edge on view of our galaxy. Our solar system is about 28,000 light years from the center. We’re rotating the center at a speed of 250 km/sec and complete one rotation every 220 million years.

THIS LITTLE PLACE WE CALL HOME

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