Earth & Space Science ~The Solar System

In e r Sci – Uni 11

I. Sun, Earth & MoonA. The Solar System

1. the sun & the objects orbiting ita. incl. 8 planets, other stars, asteroids, meteoroids, dwarf planets, comets,

dust, & gasb. everything in the universe constantly

moves & pulls on every other object1) sun = 99% of solar system’s total mass

a) causes sun’s gravitational pull that creates orbits

a) gravity also creates orbits of moons around some planets

2. The Sun a. the closest star to Earth

1) avg. 150 million km away from Eartha) it takes 8 minutes for light traveling

300,000 km per second to reach Earth b. it’s the brightest object in our sky

1) our atmosphere scatters its light during the day, blocking light of other stars

c. fairly average-size star1) 1.4 million km diameter2) 1.989 x 1030 kg (333,000X Earth’s mass)

3) avg. surface temp = 5778 K (5504.85Co)

d. Sun is the Earth’s major external source of heat & light1) sunrise & sunset result from Earth

rotating on its axis every 24 hrs.a) creates a cycle of light & dark that

affects living things & their physical processes

b) planets & distant stars become visible in the night sky

2) Sun’s energy is also the main cause of weather patterns & ocean currents

3. Planetsa. celestial bodies orbiting the sun

1) nearly round due to their own gravity & mass

a) have “hydrostatic equilibrium”

2) have cleared the area around orbital paths

b. currently, there are 8 identified planets

1) visible when their surfaces reflect sunlight

2) distance from sun determines how long it takes to orbit the sun

a) ex: Mercury (closest) = 88 days, Earth = 365.25 days, Neptune (farthest) = 60,225+ days (165 yrs)

Relative Sizes of the Planets (incl. dwarf planet Pluto)

4. Satellitesa. objects in orbit around objects with larger masses are satellites

1) over 135 known natural satellites exist in the solar system

a) range in size from less than 3 km diameter to larger than the size of Mercury

(Titan {Saturn} & Ganymede {Jupiter})

b. moons are satellites

1) all planets except Mercury & Venus have moons

2) orbit due to gravitational pull to the planet

3) reflect sunlight, making them visible

5. Earth’s moona. orbits Earth about 384,000 km awayb. surface is covered in craters & dark patches

1) craters are from collisions w/ smaller bodies

2) dark patches = mariaa) due to lava flowing from inside moon &

hardening into rockc. the moon has an impact on life on Earth due

to its gravity & movements1) ex: tidal cycles

d. has phases – different areas illuminated & seen from another body (such as Earth)

1) due to relative position of Earth, moon & sun

2) include full, half, gibbous (nearly full), crescent

3) waxing = approaching full

a) full moon = illuminated side faces you

4) waning = approaching new

a) new moon = dark side faces you

b) 29.5 days from 1 full moon to the next

e. Moon’s orbit is elliptical, so its distance from Earth changes

1) apogee = point of orbit farthest from Earth

2) perigee = point of the orbit closest to Earth

f. Eclipses are due to bodies casting shadows

*1) an event when the shadow of one celestial body

falls on another

2) Solar eclipse – when a new moon blocks the sun &

casts a shadow on Earth

3) Lunar eclipse – when a full moon passes into the

shadow of the Earth

a) visible on night side of Earth – moon darkens as

it passes through Earth’s shadow

II. The Planets

A. The Inner Planets

1. the 4 planets closest to the Sun

a. Mercury, Venus, Earth & Mars

2. classified as terrestrial planets

a. highly dense

b. relatively small

c. have a solid, rocky surface similar to Earth

1) incl. mountains, canyons & craters

d. metallic core

e. few or no moons

3. Mercury

a. closest to Sun

1) 58 million km (0.39 Astronomical Units {AU}) away

b. smallest planet

1) smaller than Earth’s moon

2) only 38% of Earth’s diameter

c. almost no atmosphere or water

1) mostly oxygen, sodium, hydrogen, helium &

potassium

2) no wind or air pressure

d. surface temperature -180o C (nightside) to 430o C

(dayside)

e. gravity = 3.7 m/s2

1) only 38% of Earth’s gravity

f. length of day = 59 Earth days

1) day = time to rotate on own axis

g. length of year = 88 Earth days

1) year = time to orbit the Sun

h. moonless & ringless

i. no evidence of life

j. named after Roman god Mercury

1) messenger of the gods and god of shopkeepers,

merchants, travelers, transporters of goods,

thieves & tricksters

4. Venus

a. 2nd closest to the sun

1) 108 million km away (0.7 AU)

b. 2nd brightest object in night sky

1) often seen from Earth near sunrise or sunset

2) referred to as “morning star” or “evening star”

c. Earth’s closest neighbor - its “twin”

1) similar in size & structure

2) surface covered in plains & volcanic mountains

d. spins opposite of most planets

1) rotates very slowly but creates hurricane-force

winds

e. gravity = 8.87 m/s2

1) only 91% of Earth’s gravity

f. its environment cannot support life as we know it

1) 465o C surface temperature

a) hottest planet in solar system

2) large amounts of CO2

& sulfuric acid in atmosphere

3) over 90X greater atmospheric pressure than on

Earth

4) however, water may have once existed

a) this could support life

g. length of day = 243 Earth days

h. length of year = 225 Earth days

i. no moons or rings

j. named after Roman goddess Venus

1) goddess of love and beauty

5. Earth

a. 3rd closest to the sun

1) 150 million km away (1.0 AU)

b. largest of the terrestrial planets

1) most of the planet is covered in water

2) surface has mountains, canyons, plains

c. only known planet to support life

1) has a hydrosphere (all of its solid & liquid water)

a) helps regulates planet’s surface temperature

2) its atmosphere contains 78% nitrogen, 21% oxygen

a) avg. surface temp kept in moderation by

atmospheric gases

b) protects from meteroids, UV radiation &

high-energy particles from the sun

d. no rings, 1 moon

e. gravity = 9.8 m/s2

f. length of day = 24 Earth hours

g. length of year = 365.25 Earth days

h. name “earth” dates back over 1000 years

1) from English/German for “ground”

2) only planet not named after Roman/Greek gods

6. Mars

a. 4th closest to the sun

1) 228 million km away (1.5 AU)

b. smaller than Earth

c. rocky surface shaped by volcanoes, impacts, winds, etc.

1) liquid water once flowed across surface

2) it has polar ice caps

a) mostly frozen CO2

but may have traces of frozen

water

d. known as the “red planet”

1) soil contains iron oxide

2) frequent dust storms have created large, red dunes

e. no rings, 2 moons

1) Phobos & Deimos

f. gravity = 3.711 m/s2

g. length of day = a little over 24 Earth hours

h. length of year = 687 Earth days

i. its environment cannot support life as we know it

1) thin atmosphere - mostly CO2, argon, nitrogen

a) allows heat to easily escape

2) surface temp -153o C - 70o C

j. named for Roman god Mars

1) god of war

B. The Outer Planets

1. the four planets farthest from the sun

a. Jupiter, Saturn, Uranus & Neptune

2. classified as “the gas giants”

a. thick, gaseous atmospheres

1) relatively small rocky cores

b. many satellites

c. rings

b. lack solid surfaces

c. a.k.a. the Jovian planets

1. Jupiter

a. 5th closest to the sun

1) 778 million km away (5.2 AU)

b. the largest planet in our solar system

1) twice as large as all other planets combined

2) 1300 times larger than Earth

3) visible from Earth w/ the naked eye

a) 4th brightest object in solar system

c. Its atmosphere includes jet streams & enormous

storms

1) create characteristic striped cloud belts & red spot

a) Great Red Spot = hurricane over 2x Earth’s diameter that’s lasted 100-350 years

d. mostly made of hydrogen & helium

1) small dense core of liquid hydrogen, rocks & ice

e. 53 known moons

1) Galileo discovered the 4 largest in 1610

a) Ganymede, Callisto, Io and Europa

b) Ganymede is larger than Mercury

c) Io has active volcanoes

d) Europa may have liquid water under ice

f. it has a faint ring (discovered in 1979 by Voyager)

g. gravity = 24.79 m/s2

g. length of day = 10 hours (a Jovian day)

h. length of year = about 12 Earth years (a Jovian year)

i. surface temperature = -148o C

j. cannot support life as we know it

a) some of its moons have oceans under their

crusts & could support life

k. first observed in ancient Babylon, 7th-8th century BC

l. named after Jupiter, king of the Roman gods

2. Saturn

a. 6th closest to the sun

1) 1.4 billion km away (5.2 AU)

2) farthest planet that can still be seen with the

unaided eye

b. 2nd largest planet in our solar system

1) 9 Earth’s would fit across its diameter

c. mostly made of hydrogen & helium

1) doesn’t have a solid surface

2) it may have a metallic core 10 times the size of Earth

d. is the least dense of all planets

1) less dense than water

e. 53 known moons, + 9 awaiting confirmation

1) largest = Titan

f. it has a prominent ring system

1) 7 main rings, w/ gaps and divisions

2) twice every 29.5 years, rings can’t be seen from Earth

a) angle of each planet puts Earth in Saturn’s ring plane

g. gravity = 10.44 m/s2

h. length of day = 10.7 hours

1) spins faster than all planets except Jupiter

i. length of year = about 29 Earth years

j. surface temperature = -148o C

k. cannot support life as we know it

1) some of its moons may be able to however

l. named after Saturn, Roman god of agriculture & wealth

1) also the root of the word “Saturday”

3. Uranus

a. 7th closest to the sun

1) 2.9 billion km away (19 AU)

b. 3rd largest planet in our solar system

1) mass is 14x greater, 4 times wider than Earth

2) visible with telescopes

c. its atmosphere is high in helium & hydrogen

1) methane gives the planet a bluish color

2) it may have a metallic core 10 times the size of Earth

3) recently confirmed that its atmosphere stinks

a) due to hydrogen sulphide (causes rotten egg smell)

d. discovered by William Herschel in 1781

1) he thought it was a star or comet, & wanted to name

it after King George

a) planet is fairly slow & dim

e. planet is tilted

1) causes planet to rotate on its side

2) may be due to collision w/ small planet soon after its

formation

f. it has 13 faint rings & 27 small moons

1) many are named after Shakespearean characters

g. gravity = 8.87 m/s2

h. length of day = 17 hours

1) like Venus, it rotates backwards (retrograde)

i. length of year = 84 Earth years

j. surface temperature = -216o C

1) doesn’t vary w/ seasons since it’s so far from the sun

k. cannot support life as we know it

1) over 80% of its mass is a fluid mix of water, methane &

ammonia ices

l. named after Ouranos, Greek god of the sky & heavens

1) only planet named after a Greek deity

2) named by astronomer Johann Bode

4. Neptune

a. 8th closest to the sun

1) 4.5 billion km away (30 AU)

b. because of Pluto’s elliptical orbit, Neptune is sometimes

farther from the Sun than Pluto

c. its atmosphere is mostly hydrogen, helium & methane

d. discovered by Johann Galle in 1846

1) 1st planet whose existence was determined

mathematically

2) Galileo had seen it, but thought it was a star due to

its slow motion

e. it has 6 rings & 13 known moons

1) moons are named after Greek sea gods & nymphs

2) largest moon = Triton

f. gravity = 11.15 m/s2

g. length of day = 16 hours

h. length of year = 165 Earth years

i. surface temperature = -214o C

j. named after Greek & Roman god of the sea, Neptune

k. cannot support life as we know it

1) surface is fluid mix of ammonia & methane ices

2) too far from sun to be illuminated well

3) has great storms & winds that reach over 2400 km/hr

a) they are linked to the Great Dark Spot - a very large,

dark storm in Neptune’s atmosphere

b) strongest winds in the solar system