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Transcript
OUR SOLAR SYSTEM
FORMATION OF OUR SOLAR SYSTEM
• Our solar system is believed to have formed from a
nebula
• Nebula—A cloud of dust and gas in space
• Nebulae begin rotating slowly and speed up as they
contract.
• Nebular Theory—the sun and planets formed from a
rotating disk of dust and gases
• As the speed increased, matter became concentrated in the
center where the sun eventually formed.
PLANETESIMALS
• Planets were formed as matter collided and clumped
together.
• Planetesimals—small irregularly shaped bodies formed by
matter colliding.
• Grew larger with more collisions until large enough to exert a
gravitational pull on surrounding objects, growing even larger.
• Inner planets—closer to the sun, higher temperatures, formed
objects with higher melting points
• Outer planets—further from the sun, colder temperatures, ices
formed
SOLAR SYSTEM DETAILS
• Approximately 99.85% of the mass of our solar system is
in the sun (0.15% planets)
• This large mass causes a very large gravitational pull causing
the planets to orbit.
• All planets orbit the sun in the same direction
• 7 planets orbit on the same plane as the sun (within 3°)
• Mercury’s orbit is inclined by 7°
PLANETS
• Terrestrial Planets—Mercury, Venus, Earth, and Mars
• The inner planets
• Relatively small, 5x density of water
• Terrestrial = Earth-like
• Jovian Planets—Jupiter, Saturn, Uranus, Neptune
• The outer planets
• Huge gas giants
• 1.5x density of water – Saturn 0.7x density of water, will float
• Jovian = Jupiter-like
WHAT MAKES UP THE PLANETS?
• The substances that make up planets are divided into 3 groups:
gases, rocks, & ices.
• Gases—hydrogen & helium (have low melting/freezing points)
• Rocks—mainly silicate materials & metallic iron (high melting points)
• Ices—include ammonia (NH3), methane (CH4), carbon dioxide (CO2), and
water (H2O) (intermediate melting points)
• Terrestrial Planets: mostly rocky & metallic substances. Only minor
amounts of gases & ices.
• Jovian Planets: large amounts of gases (H & He) and ices (mostly H2O,
NH3, & CH4). Some rocky material is concentrated in their cores.
ATMOSPHERES OF THE PLANETS
• Jovian planets: very thick atmospheres of mostly hydrogen,
helium, methane, and ammonia.
• Terrestrial planets: thinner atmospheres
• Mass & Temperature affect a planet’s atmosphere
• Mass: larger mass causes a larger gravity to keep gases from
escaping
• Temperature: higher temps cause gases to move faster, so they
can reach escape velocity (velocity needed to escape gravity)
23.2 THE TERRESTRIAL PLANETS
• Studied by space crafts, probes, & rovers taking pictures and
collecting samples from our closest neighbors.
MERCURY
• Innermost & smallest planet (slightly larger than our moon)
• Dark gray in color due to rocky surface of igneous silicate rocks
& dust.
• Similar features to our moon: highlands, craters, & smooth
areas like maria.
• Unlike the moon, it is very dense and has a large iron core.
• Thinnest atmosphere of all the planets--mostly oxygen, sodium,
hydrogen, and helium
• The greatest temperature extremes of any planet -173°C to 427°C
• Revolves around the sun quickly, but rotates slowly
• No moons
VENUS
• 2nd planet from the sun—similar to Earth in size, density,
mass, & tectonic activity (a.k.a. “Earth’s twin”)
• Atmosphere is much more dense than Earth
• Mostly carbon dioxide, nitrogen, and sulfuric acid clouds
• Creates a runaway greenhouse effect, trapping heat and
heating the planet.
• Hotter surface than Mercury (475°C)
• Appears reddish orange due to the sun hitting its atmosphere
• Surface features (mapped with radar pulses): mostly planes, lava
flows, lava channels, & volcanoes due to tectonic activity & volcanism
• No moons
MARS
• “The Red Planet” last terrestrial planet
• Atmosphere only 1% density of Earth’s
• Carbon dioxide & traces of water vapor
• Extensive dust storms causes Mars’ color to change
• hurricane force winds last for weeks
• Surface features: numerous inactive volcanos (largest Olympus
Mons 2 ½ x Mount Everest), craters, canyons (formed by
material slipping along faults)
• Temperatures range from -70°C to -100°C
• 2 moons: Phobos & Deimos (captured asteroids)
WATER ON MARS?
• Polar ice caps of water ice covered by frozen
carbon dioxide
• Liquid water?
• Evidence: drainage patterns similar to those created by streams on Earth &
ancient “islands” in dry streambeds
• Water may have existed in Mars’ atmosphere causing downpours which may
have produced the channels.
• Many scientists do not accept this theory of Mars. Stream-like valleys
may have formed by collapsing after subsurface ice melted.
• Liquid water is essential to life, so finding evidence of it on Mars is
exciting
THE OUTER PLANETS
JUPITER
• Largest, most massive planet in our solar system (1/800 the mass of the sun)
• 2.5x greater than the mass of all other planets & moons combined
• Rotates fastest of all the planets (1 day = 10 Earth hours)
• Covered in alternating bands of multicolored clouds parallel to the equator
caused by winds.
• Great Red Spot: a cyclonic storm in Jupiter’s southern hemisphere.
• Under the thick atmosphere Hydrogen is compressed to a liquid
• Jupiter is covered by a gigantic ocean of liquid hydrogen
• Contains a rocky, metallic core
• 63 moons discovered so far (4 largest: Io, Europa, Ganymede, & Callisto)
• Io is 1 of only 4 volcanically active bodies in our solar system
SATURN
• Very active atmosphere: winds up to 1500km/hr
• Cyclonic storms similar to Jupiter’s red spot.
• Most prominent feature: rings
• Categories based on density
• A & B are very dense, larger particles, lightest colors
• C & D are also quite dense, but made of different materials (darker)
• E, F & G outermost rings, less dense, fine particles & faint
• 56 moons
• Titan is largest—larger than Mercury
• Contains liquid hydrogen
• One of only 2 moons that has an atmosphere (the other is Triton)
• Enceladus is volcanically active
URANUS
• Most planets spin on an axis perpendicular to their orbit
• Uranus’ spin is nearly parallel to its orbital axis
• Rotates on its side
• Appearance of rolling
• 27 moons that we know of
• 5 largest moons have varied terrain
• Miranda has the greatest variety of land forms of any body
in our solar system
NEPTUNE
• The windy planet
• Dynamic atmosphere like Jupiter & Saturn
• Winds exceed 1000 km/hr
• Windiest planet in our solar system
• Great Dark Spot: a storm like Jupiter’s Great Red Spot, moves
around the planet
• Cirrus-like clouds of frozen methane
• 13 known moons: Triton is largest (≈ size of our moon)
• Triton experiences retrograde motion
• Must have formed independently and was captured by Neptune
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WHICH PLANETS HAVE RINGS?
Originally thought to be unique to Saturn
All 4 Jovian planets have rings
Rings differ in detail, number & density
All have multiple concentric rings separated by gaps of varying
widths
Each ring is made of individual particles of ice & rock: “moonlets”
Jupiter’s rings are very faint, widely dispersed, fine dark particles
similar to smoke particles
Saturn has the most dense rings
Uranus’ rings were discovered when the planet passed in front of a
star and something on the edges blocked its view.
Neptune has 5 primary rings of dark material
PLUTO
• No longer considered a planet, “dwarf planet” since 2006
• Dwarf Planet—a round object that orbits the sun but has not cleared
the area around its orbit
• Gravity is too weak to attract nearby debris
• Orbits in a zone with other small bodies
• Made of a combination of ice & rock
• Ceres (in asteroid belt) discovered in 1801
• Eris, larger than Pluto discovered in 2005
• Pluto has 5 moons: 1 large moon—Charon over ½ the size of Pluto
• Charon may be considered a dwarf planet itself
ASTRONOMY MODELS
• Models of the solar system and other space models
are often not drawn or built to scale
• Scaled Model—a physical representation of an object
or system which maintains accurate relationships
between certain aspects of the model, but actual
values of the original objects are not preserved.
• Relative Sizes are often used instead of scaled
models for space
• Objects in space vary widely in size and distance
• Space objects are often put in relative order from largest to smallest (or nearest to
farthest), not considering the AMOUNT of size difference between them.
• Our Toilet Paper model of the size of the solar system was to scale
• Our Paper Mache solar system will use relative sizes
JUST HOW
BIG IS THE
SOLAR SYSTEM?
SOLAR SYSTEM
9* PLANETS
Earth
Sun
Venus
Mars
Mercury
Jupiter
Saturn
Neptune
Uranus
Venus
Earth
MINOR MEMBERS OF THE SOLAR SYSTEM
• Asteroids—small rocky bodies that orbit the sun
• Larger than 10 m in diameter
• Largest: dwarf planet Ceres (1000 km in diameter)
• Most are in the asteroid belt between Mars & Jupiter
(orbital period of 3-6 years)
• Most have irregular shapes (may be fragments of a broken
planet between Mars & Jupiter but there isn’t enough mass
to support this)
COMETS
• Comets—pieces of rocky & metallic materials held
together by frozen water & gases (NH3, CH4, CO2, & CO)
• Very elongated orbits taking them beyond Pluto
• Orbital periods of less than 200 yrs to hundreds of thousands of years
• Distant from the sun they are very small, as they approach the sun, frozen
gases begin to vaporize causing them to expand & form a tail.
• Parts of a comet
• Coma: glowing head
• Nucleus: small bright core within the coma (few km in diameter)
• Tail: trailing dust and gases (extends millions of km)
• The ion gases trail at the top of the tail and the dust trails at the bottom.
• Always points away from the sun (due to radiation pressure & solar wind)
WHERE DO COMETS COME FROM?
• Kuiper Belt: Region beyond Neptune
•
•
•
•
Comets with short orbital periods
Move in nearly circular orbits on the same plane as the planets
Collisions may alter their orbit, sending them into the inner solar system
Halley’s Comet comes from this region.
• Potato-shaped nucleus pitted with craters
• 1.6 million km tail was visible during daylight in 1910
• Oort Cloud: Spherical shell around our solar system
• Comets with long orbital periods
• Not confined to the plane of our solar system
• Highly elongated orbits
METEOROIDS, METEORS, & METEORITES
• Meteoroid—small particle that travels through space
• Most are as small as sand grains
• Originate from 3 places:
• Interplanetary debris (not collected by planets)
• Small pieces of material in the asteroid belt
• Solid remains of comets
• Meteor—a meteoroid that enters Earth’s atmosphere and burns up
(shooting star)
• Meteor showers: up to 60+ meteors per hour, often associated with the
orbits of comets
• Meteorite—a meteoroid that reaches Earth’s surface.
• One of the few large meteorites to hit Earth is Meteor Crater in Arizona.
AGE OF THE SOLAR SYSTEM
• Evidence from meteorites, moon rocks, & Earth
rocks were used to determine the age of the solar
system.
• Radiometric dating of meteorites were found to be
4.57 billion years old
• Oldest known materials in our solar
system
• Mostly iron