Download Int. Sci. 9 - Universe Powerpoint

The Solar System
History of Our Solar System
• Geocentric Model – A.D. 140 Egyptian
astronomer Ptolemy
– Means Earth is in the center and everything else
revolves around it
– Explained most observations made at that time
• Heliocentric Model – early 1500s Polish
scientist Nicolaus Copernicus
– Means the Sun is in the center and everything
else revolves around it
– Galileo Galilei & other scientists later proved
this model was correct
What’s in Our Solar System?
• Our Solar System consists of a central star
(the Sun), the 8 planets orbiting the sun,
moons, asteroids, comets, meteors,
interplanetary gas, dust, and all the “space”
in between them.
• The 8 planets of the Solar System are
named for Greek and Roman Gods and
Goddesses.
Inner and Outer Planets
• Inner Planets:
– Mercury
– Venus
– Earth
– Mars
• Outer Planets:
– Jupiter
– Saturn
– Uranus
– Neptune
Planetary Orbits
• Johannes Kepler, 1600, discovered that the
orbit of a planet around the sun is not a
CIRCLE but an ELLIPSE – Looks like an oval that has been stretched
– The force that holds the planets in orbit around
the sun wasn’t understood until Isaac Newton’s
discoveries about gravity.
– Gravity & Inertia combine to keep the planets
in orbit around the sun
The Relative Size of the Planets in
the Solar System
One astronomical unit (AU) = avg. distance
from Earth to the Sun – 149,598,000 km
Exploring the Solar System
• Modern technology – telescopes, piloted
spacecraft, space probes, etc.
• 1st artificial satellite – Sputnik, 1957
• 1st human to orbit Earth – Yuri Gagrin, April 1961
• 1st American in space – Alan Shepard, May 1961
• 1st man on the moon – Neil Armstrong, July 1969
The Sun
• The sun’s energy comes from
nuclear fusion (where hydrogen is
converted to helium) within its
core. This energy is released from
the sun in the form of heat and
light.
• Remember: Stars produce light.
Planets reflect light.
• A star’s temperature determines its
“color.” The coldest stars are red.
The hottest stars are blue.
The 8 Planets of the Solar System
• Planets are categorized according to
composition and size. There are two main
categories of planets:
– Terrestrial (small & rocky) (Mercury,
Venus, Earth, and Mars)
– Gas Giants (Jupiter, Saturn, Uranus, and
Neptune)
Characteristics of Small Rocky
Planets
•
•
•
•
•
They are made up mostly of rock and metal.
They are very heavy.
They move slowly in space.
They have no rings and few moons (if any).
They have a diameter of less than 13,000
km.
• They are much warmer on average
Mercury
• Revolution period of 88
days.
• Smallest & closest to the sun
• Large iron core; geologically
dead
• Extreme temp fluctuations
• Scientists believe there is
ICE on Mercury! The ice is
protected from the sun’s heat
by crater shadows.
Venus
• Its maximum surface temperature
may reach 900F.
• Venus has no moons and takes 243
days to complete an orbit.
– Rotation is longer than revolution
• Unusual rotation – rotates in the
opposite direction to which it
revolves
• Thick atmosphere – mostly CO2
which raises the planet’s temp
• Brightest object in Earth’s night sky
– Often mistaken as a star
Earth
• Earth is the only planet
known to support living
organisms.
• Earth’s surface is composed
of 71% water.
– Water is necessary for life on
Earth.
– The oceans help maintain
Earth’s stable temperatures.
• Earth has one moon and an
oxygen rich atmosphere.
Earth’s Moon
• It takes the moon approximately 29 days to
complete one rotation. The same side of the moon
always faces us.
• The moon’s surface is covered in dust and rocky
debris from meteor impacts.
• The moon reflects light from the sun onto the earth’s
surface.
• Hypothesis = the moon formed after an enormous
collision early in Earth’s history
Earth-Moon System
• Lack of an atmosphere causes the surface temp. to
vary greatly
• Evidence of ice near the moon’s N and S poles
• Major features:
– Maria – low, flat plains formed by ancient lunar lava flows;
cover about 15%
– Highland – surround Marias & are lightly colored; rough,
mountainous ranges
– Craters – round depressions caused by an impact of high speed
meteoroids
Earth-Moon System
• Thousands of craters are evidence that the
moon is geographically dead
– Little erosion
– No plate motion
Phases of the Moon
Eclipses
• Occurs when a shadow of one body in space
falls on another
– For an eclipse to occur on Earth, the sun, moon,
and Earth must lie along a straight line
– Infrequent because the plane of the moon’s
orbit is tilted about 5 degrees
• Solar – occurs when the moon casts a
shadow on a portion of Earth’s surface
• Lunar – occurs when Earth casts a shadow
on the moon
Tides on Earth
• Regular rise and fall of ocean waters
• Caused mainly by differences in the moon’s
gravitational pull on Earth
Mars
• “Red Planet” – iron rich rocks
• Like Earth, Mars has ice caps
at its poles.
• Mars has the largest volcano in
our solar system: Olympus
Mons. Olympus Mons is
approximately 15 miles high.
• Shows evidence of once having
liquid surface water
• Mars has two moons and takes
about two years to complete an
orbit.
Beyond Mars
• Asteroids – small, rocky bodies
– Asteroid belt – beyond mars, orbiting the sun
• Scientists hypothesize that asteroids are
remnants of the early solar system that
never came together to form a planet
Characteristics of Gas Giants
• They are made up mostly of gases
(primarily hydrogen & helium).
• Massive & very light for their size.
• Very cold temps
• Move quickly in space.
• They have rings and many moons.
• They have a diameter of less than 48,000
km
Gas Giants
• Rings – disk made of many small particles
of rock & ice in orbit around a planet
Jupiter
• Jupiter is the largest and most
massive planet.
• Composed mainly of hydrogen &
helium
• It’s diameter is 11 times bigger than
that of the Earth’s.
• Rotates rapidly – 1 day on Jupiter is
less than 10 Earth hours
• It takes about 12 years for Jupiter to
orbit the sun.
• Jupiter has at least 63 moons.
Jupiter’s Moons
• Ganymede & Callisto – similar size to
Mercury
• Io & Europa – about the size of our moon
• Europa – icy crust appears to rest on top of
a liquid saltwater ocean; scientists
hypothesize that Europa is the most likely
place in the solar system to support life
(other than Earth obviously)
Saturn
• 2nd largest planet; most visible from
Earth
• Saturn is composed almost entirely of
hydrogen and helium.
• Saturn has many rings made of ice.
Saturn’s rings are very wide. They
extend outward to about 260,000
miles from the surface but are less
than 1 mile thick.
• Atmosphere is the largest of any
planet
• Lowest average density of any planet
• Saturn has at least 56 moons, some of
which orbit inside the rings!
– Titan – larger than Mercury
• It takes Saturn about 30 years to orbit
the sun.
Uranus
• Uranus is blue in color
due to methane gas in its
atmosphere.
• Uranus has 11 dark rings
surrounding it.
• Uranus has at least 27
moons and takes 84
years to complete one
orbit.
• Very cold
• Unusual tilt – lies
nearly on its side @
more than 90 degrees
Neptune
• Neptune has the fastest
winds in the solar
system: up to 2,000
km/hr.
• Neptune is also blue in
color due to methane gas
in its atmosphere.
• Neptune takes 165 years
to orbit the sun and has
at least 13 moons.
• Large storms in its
atmosphere – Great Dark
Spot 1989
Dwarf Planets
• Like a planet, spherical & orbits the sun
directly
• Unlike a planet – has not cleared the
neighborhood around its orbit
• Pluto – very small
– Elliptical orbit
– Tilted more than 90 degrees like Uranus
Comets & Meteoroids
• Comet – dusty pieces of ice & rock that
partially vaporize when they pass near the
sun
• Meteoroids – pieces of rock, usually less
than a few hundred meters in size
Edge of the Solar System
• Estimate thousands of solar system objects
exist beyond Neptune’s orbit
– Kuiper Belt – extends about 100 AU from
Neptune;
• Objects are mostly made of ice, dust, & rock
• Pluto is found here
– Oort Cloud – great reservoir of comets
Exploring the Universe
The Sun
• Tremendous amounts of energy in the form
of electromagnetic radiation
– Produced in its central region by the fusion of
hydrogen nuclei into helium nuclei
Forces in Balance
• Astronomers estimate the sun will remain
stable for another 5 billion years
• Energy from nuclear fusion in the center of
the sun causes ions to move faster, exerting
an outward thermal pressure
– At the same time, gravity pulls the gas inward
The Sun’s Interior
•
•
•
Core – nuclear fusion occurs;
little more than ¼ of the sun
Radiation Zone – region of
highly compressed gas; energy
is transferred by the
absorption & reradiating
electromagnetic waves
Convection Zone – outer
layer of the sun’s interior;
energy is transferred outward
mainly by convection currents
The Sun’s Atmosphere
• Protosphere –
innermost layer
• Chromosphere –
middle layer; gives off
color
• Corona – outermost
layer
Features of the Sun’s Atmosphere
• Sunspots – areas of gas
in the photosphere that
are cooler than the
surrounding gases
• Prominences – huge
loops of gas that erupt
from sunspot regions
• Solar Flare – sudden
release of energy from the
sun usually near sunspots
Sun’s Energy
The sun will eventually lose energy & become a
white dwarf!!
Stars
• Large, glowing ball of gas in space, which
generates energy through nuclear fusion in
its core
– Closest star to Earth = Sun
Distances to the Stars
• Light year – distance that light travels in a
vacuum in a year; about 9.5 trillion years
• Scientists cannot measure stars distances
directly
– Parallax – apparent change in position of an
object with respect to a distant background
Properties of Stars
• Classified based on their color, size, &
brightness
– Color & Temp – hottest stars are blue
– Brightness – decreases as its distance from you
increases
• Apparent brightness – brightness of a star as it appears
from Earth
• Absolute brightness – how bright the star really is
– Size & Mass – calculate the mass by observing the
gravitational interaction of stars that occur in pairs
Star Composition
Hertzsprung-Russell Diagram
Hertzsprung-Russell Diagram
• Used to estimate the sizes of stars & their
distances, and to infer how stars change over time
• Main Sequence Stars – about 90% of stars
– The Sun lies in the middle of this band
• Supergiants – less than 1%; very bright stars at
the upper right of the diagram
• White Dwarf – about 10% of stars; small, dense
remains of low or medium mass stars
How Stars Form
• Nebula – large cloud of gas and dust spread
out over a large volume of space
• Stars form in the densest regions of nebulae
by the pulling by gravity
• As the nebula contracts, it heats up
• Protostar – contracting cloud of gas & dust
with enough mass to form a star
How Stars Form continued…
• As a protostar contracts, its internal pressure
& temp continue to rise
• A star is formed when a contracting cloud
of gas & dust becomes so dense & hot that
nuclear fusion begins
• New stars enter the Main Sequence stage
Adult Stars
• A star’s mass determines the star’s place on
the main sequence & how long it will stay
there
• Stars spend 90% of their life as main sequence
– Nuclear fusion is occurring @ a stable rate
• Amount of gas & dust available when a star
forms determines the mass of each young star
• A star ends up as a white dwarf, neutron star,
or black hole once it exhausts its fuel supply
The Death of a Star
• Dwindling supply of fuel in the star’s core
• Low & Medium Mass stars eventually turn
into White Dwarfs
• High Mass stars result in a supernova
(explosion)
– Its core continues to collapse & either become a
neutron star or a black hole
Groups of Stars
• Open Clusters, Associations, & Globular
Clusters
– Open cluster – often contain bright supergiants
& gas & dust clouds
– Globular cluster – large group of older stars
Galaxies
• Huge group of individual stars, star
systems, star clusters, dust, & gas bound
together by gravity
– Spiral
– Elliptical
– Irregular
Hubble’s Law
• The speed @ which a galaxy is moving
away is proportional to its distance from us
• “the red shift” refers to galaxies shifting
toward the red wavelengths (getting farther
away from Earth)
• Galaxies that are farther away  moving @
a faster speed
Evidence for the Big Bang theory
• Existence of cosmic microwave background
radiation
• Red shift in the spectra of distant galaxies