A Tour Of The Solar System

Galaxies

Galaxies are huge regions of space that contain the stars, planets, and other astronomical featuresThey can have many shapes

SpiralEllipticalIrregular

Our galaxy is known as the milky way galaxyHttp://www.astro.Princeton.edu/~frei/Gcat_htm/cat_ims.htm

Milky Way Galaxy

80,000 light years acrossSpiral shaped with 4 armsWe are located in the Orion armNearest neighbor is Andromeda (2.2 Million light years)

Solar System

Origin of the Solar SystemThe solar system began as nothing more than dustGravity caused the dust to condense and spinAs the cloud gets hotter and denser fusion takes placeThe fusion results in the birth of a star

Proto – Planetary DiscAs our star, the sun, is being formed it is surrounded by a disc of debris and gasThese particles interact and accumulate to form the plantsWhen the sun forms it emits solar windThis wind pushes lighter material outward (the gases)

The SunOne of more than 100 billion in our galaxyRotates about the nucleus at about 137 miles/sec Takes about 200 million years to complete a rotationAccounts for 99.8% of the mass of our solar system

The Sun Cont.

The sun is the center of the solar systemBecause it is so massive all of the planets are captured in its gravity field and orbit itComposed of 75% hydrogen and 25% heliumThe core is about 15.6 million KelvinThe surface, photosphere, is about 5800 K

The Planets

There are 9 planets that orbit the sunThe orbit is in an elliptical pathThe plane along which the planets orbit is known as the ecliptic

The Earth3rd rock from the sun (5th largest)149,600,000 km from the sunRotation: 23 hr 56 minOrbit: 365.26 daysMass: 5.97 x 1024 kgGravity: 1.0Obliquity: 23.5 degrees

Formation of the EarthThe earth was formed from accreted particles in the proto-planetary disc about 4.6 GaAs the material was accreted it began to differentiate (responsible for internal layering)The denser material sank towards the center (iron core)Lighter material rose towards the top (crust)

SeasonsThe earth spins about an axis that is at an angle of 23 degrees with the eclipticThis angle causes different regions of the earth to experience variable amounts of sunlight throughout the year

Earth’s Magnetic FieldThe liquid outer core of the earth is in a state of convectionThis convection is responsible for a magnetic field about the earthThe magnetic field of the earth resembles that of a bar magnetSolar wind from the sun interacts with the magnetic field to create the northern lights

Aurora Borealis

Earth’s Oceans and Atmosphere

The earth is distinguishable from the other terrestrial planets because of its surface waterWater accounts for 71% of the earth’s surface

The earth’s atmosphere is 77% nitrogen and 21% oxygenThe atmosphere helps block out harmful rays and maintains the surface temperature

The MoonEarth’s only satellite384,000 km from earth1738 km radiusMass: 0.07 x 1024 kgGravity: 0.16Orbit: 27.32 daysRotation: 27.32 days4.4 Ga oldNo:

Magnetic fieldOceansPlate tectonicsAtmosphere

Moon Formation

During the earth’s formation a large object collided with the earthThe ejected material is the moonDifferentiation was already in process so the moon is composed of the lighter external materials (largely basalts)

Moon’s SurfaceThe surface of the moon is composed largely of basaltsThe major surface feature are craters from meteoroid impactsEvidence of lava flows exist for impact craters greater than 100 km

The Moon’s RotationThe rotation of the moon is the same as the orbit.This implies that we always see the same side of the moon.The phase of the moon that we see depends on the moon’s location relative to the sun

MercuryClosest planet to the sun (58 million km)Second smallest planet 2,439 km radiusMass: .33 x 1024 kgGravity: 0.38Orbit: 87.96 daysRotation: 58.65 days

Mercury Rotation

Mercury rotates 1.5 times per each orbitThis 3:2 ratio causes the mercury day to be extremely long (176 earth days)During the day the surface can get as hot as 700 KDuring the night the surface cools to 100 K

Mercury SurfaceDominated by craters and basins

Cratering took place early (ended 3.8 Ga)

Largest basin: Caloris Planitia

1300 km diameter

Plains regions also exist

Evidence of lava flows

Scarps are other surface features

Evidence of contraction

Mercury’s Interior

Despite its small size, mercury is very denseImplies internal composition must be ironPresence of a magnetic field (1% of earth’s) confirmed thisTo account for magnetic field and density, mercury is 70% metal and 30% silicatesBelieved that a large impact after differentiation ejected most of the silicate material

Water / Atmosphere

No surface water exist on the surface of mercuryPotentially ice located in craters that see little sun (polar regions)

Possesses a thin atmosphereAtmosphere is surface material lifted by solar wind interaction

Venus

2nd planet from the sun (108 million km)Radius: 6,052 kmMass: 4.87 x 1024 kgGravity: 0.76Orbit: 224.7 daysRotation: 243 days

Atmosphere

Very thick cloud coverAtmosphere composed mostly of carbon dioxideClouds composed of sulfuric acidEffect is a runaway greenhouseSurface pressure: 90 atm (the same as 1 km depth in earth’s oceans)Surface temperature: 700 K

Venusian SurfaceVery dryYoung (500 my)Mostly lava plainsTwo regions of major relief

Ishtar terra (polar)Aphrodite terra (equatorial)

Few impact cratersVolcanic features

Venus InteriorVenus is very similar to earth in size, mass, and distanceImplies similar interior structureThe core of Venus is still hot from formation and radioactive materialsImplies the mantle convects

Plate Tectonics?Although Venus is currently inactive, did plate tectonics exist in the past?Young surface age believed to be result of global overturn.The overturn marks the transition from a mobile lithosphere to a stagnant lithosphere.

Venus Rotation

The obliquity of Venus is nearly 180 degrees.The effect of this is a retrograde rotation.On Venus it would appear as if the sun rose in west and sat in the east.

Mars

4th planet from the sun (228 million km)Radius: 3393 kmMass: 0.64 x 1024 kgGravity: 0.39Orbit: 686.98 daysRotation: 24 hrs 37 min

Mar’s Rotation / AtmosphereMars has an axial tilt of 25.Orbital period is nearly twice that of the earth’s so seasons are nearly twice as long.Tilt and highly elliptical orbit results in temperature variations from 140 K to 300 K.

The atmosphere of mars is very thinComposed primarily of CO2

Seasonal dust storms results in a lot of dust in the atmosphereSmall % of water in atmosphere can produce clouds

Martian Atmosphere

Martian SurfaceFeatures include:

Shield volcanoes:• Olympus Mons (24

km high and 550 km wide)

Patera:• Shield volcanoes

that do not rise very high but extend for great distances.

Channels:• Valles Marineris

(3000 km long, 8 km deep, and 600 km wide)

Southern hemisphere heavily cratered while northern hemisphere is notInactive

Water?Mars contains polar capsChannels suggest water at some point in the martian historyCurrent hypothesis:

Water is located beneath the surface (much like permafrost on earth)

Martian Interior

Smaller so had longer time to coolLess dense so core probably has sulfer and iron compositionCore is 1700 km thickMantle: 1300 kmCrust: 80 km

Is There Life on Mars?

Popular notion since LowellBelieved that seasonal color changes were evidence of vegetation and channels were man madeRecent findings indicate some biological activity

Moons Of Mars

Two moons: Deimos and PhobosBoth carbon rich but low density suggest both contain ice as wellProbably astroids captured by mars gravityDeimos smallest moon in solar system (6.3 km radius)Phobos: 11 km radius but only 6000 km above surface

Jupiter

5th planet from the sun (778.3 million km)Radius: 71,398 kmMass: 1900 x 1024 kgGravity: 2.74Orbit: 4,333 daysRotation: 9 hrs 50.5 min

Jupiter CompositionLikely to have a rocky core (10 - 15 x the mass of the earth)Above the core there exist liquid metallic hydrogen

Only exist at pressures > 4 million barsConsist of ionized protons and electrons (source of magnetic field)

Outermost layer is regular hydrogen and heliumWe actually observe the clouds of Jupiter

Jupiter’s CloudsVariable composition consisting of:

Ammonia iceAmmonia hydrosulfideWater and ice

Confined to bands of latitude that rotate in opposite directionsMost prominent feature is the GRS

High pressure zone (rises higher than surrounding clouds)

Jupiter’s RingsVoyager discovered in 1971Contains no iceVery thin and darkComposed of rocky material probably from the inner four moonsConstantly replenished since atmospheric and magnetic field deplete them

Jupiter’s MoonsAt least 164 largest (Galilean):

CallistoIoGanymedeEuropa

4 inner moons:ThebeMetisAndrasteaAmalthea

Io

It is the center of a tug-a-war between Ganymede, Europa, and JupiterThe effect is intense tidal volcanic activitySurface temperature is low (-143 C)Has a solid core surrounded by a rocky shell of silicate? Composition

Europa

Europa consist of a metallic core, a silicate rock layer, and water.The outer ice shell of Europa is crisscrossed by dark bands.Beneath the ice shell there is potentially large oceans.Water exist because of tidal heating.

Saturn

6th planet from the sun (1427 million km)Radius: 60,000 kmMass: 569 x 1024 kgGravity: 1.17Orbit: 10,579 daysRotation: 10 hrs 14 min

Saturn Composition

Saturn’s interior is similar to Jupiter’s.

Rocky core, metallic hydrogen, hydrogen, helium, trace elements

Density less than that of waterAlso possesses cloud coverClouds trapped in bands of latitude that rotate at variable speeds

Fastest at the equator

Ring System of Saturn

Ring System of Saturn

Most interesting featureVery thin (1.5 km thick) despite large diameter (250,000 km)Composition is largely ice and rocky particles coated with iceBroken into different regionsOrigin unknown but must have some mechanism to replinish

Resonance of moons

Moons of Saturn18 to dateAll have densities less than 2 gm/cm3

30 – 40% rock60 – 70% ice

Most interact with one another to produce stable and synchronous orbitsTitan is by far the largest with a radius of 2575 km

Once believed to be bigger but enormous atmosphere threw off calculations

Uranus

7th planet from the sun (2871 million km)Radius: 25,559 kmMass: 87 x 1024 kgGravity: 0.94Orbit: 30,685 daysRotation: 17 hrs 14 min

Neptune

8th planet from the sun (4497 million km)Radius: 24,800 kmMass: 103 x 1024 kgGravity: 1.15Orbit: 60,188 daysRotation: 16 hrs 3 min

Composition

Small rocky cores (3% of their mass)Thick layer of rock and ice (85% of their mass)

Most likely in a liquid state (mud)

Atmosphere of hydrogen, helium, and trace materialsSimilar to Jupiter and Saturn without the liquid metallic hydrogen

AtmosphereThe striking blue color of these two planets is due to methane gas

Methane absorbs red light and reflects blue

Majority of the atmosphere is hydrogen and heliumCloud features are more prominent on NeptuneNeptune once contained GDS (half the size of the GRS)

Axial Tilt

Neptune: 29; Uranus: 98As a result both planets experience seasonsOn Uranus the polar regions receive more sunlight yet equatorial regions are hotterLack of storms on Uranus as compared to Jupiter, Saturn, and Neptune believed to be b/c of orientation

Rings

Both planets possess ringsLike Jupiter they are dark (charcoal color)Compositon is unknownUranus:

11 distinct regions

Neptune:4 distinct regions

Uranus SatellitesContains the most moons (24)Named after the writings of Shakespeare and pope3 classes:

11 small dark inner ones5 large onesOuter new ones

Largest is Titania (789 km)

Neptune Satellites

8 known moonsLargest of which is Trition (1350 km)

 Naiad Thalassa Despina Galatea Larissa Proteus Trition Nereid

Pluto

9th planet from the sun (5913 million km)Radius: 1,140 kmMass: 0.01 x 1024 kgGravity: 0.03Orbit: 90,700 daysRotation: 6.387 days

Orbit

The orbit of Pluto is very eccentricDuring 20 of its 249 year orbit it is closer to the sun than NeptunePluto and Charon have the same rotation period

Composition

Average density is 1.8 – 2.1 g/cm3

Implies 50 – 75% rock

Charon: 1.2 – 1.3 g/cm3

Icy surface composed of:98% nitrogenTraces of methane and carbon monoxide

Atmosphere is thin, constantly freezes, and falls to the surface

Asteroids and Comets

Believed to be remnants of primordial planets that were destroyed or never formed.Therefore, they provide detailed information about past conditions.Believed to originate in two locations.

Asteroid belt and Kuiper belt, respectively.

CompositionsAsteroids:

C-type: (75%) same composition as sun minus hydrogen and heliumS-type: (17%) nickel-iron mixed with iron and magnesium silicatesM-type: (8%) pure nickel-iron

Comets:Mixture of non-volatile grains and frozen gases

Web SourcesAmazing space web based activities

Interactive games and lessonsHttp://amazing-space.stsci.edu/

BrainPopGreat movieHttp://www.brainpop.Com/science/space/solarsystem/

Build a solar systemHow to build a scaled solar systemHttp://www.exploratorium.edu/ronh/solar_system/

NASA’s ObservatoriumGamesHttp://observe.ivv.nasa.Gov/nasa/fun/fun_index.shtml.Html

Space and astronomyLessonshttp://www.athena.ivv.nasa.gov/curric/space/

Web SourcesGalaxy Catalogue

Images of various galaxieshttp://www.astro.princeton.edu/~frei/Gcat_htm/cat_ims.htm

Nine PlanetsLessons on the nine planetshttp://www.seds.org/nineplanets/nineplanets/nineplanets.html

SeasonsExperiment to show cause of seasonshttp://faldo.atmos.uiuc.edu/w_unit/LESSONS/seasons.html

Virtual Solar SystemLessonshttp://freespace.virginnet.co.uk/solar.system/index.html

Views of the Solar SystemBio and pictures of the planetshttp://www.hawastsoc.org/solar/eng/homepage.htm