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The Universe, Solar System,
and Planets I
Questions:
How do we know the Big Bang happened?
How do we know the Universe is expanding?
What is the timeframe of Universe evolution?
News Flash: NASA/CNN report first starsformed early than once thought
Edwin Hubble at Mt. Wilson
Hubble guiding the Hooker
100 inch telescope in 1923.The Hooker 100 inch telescope atop Mt. Wilson
near Pasadena, CA. It was the largest telescope in
the world from 1917-1947.
Hubble’s observations at the 100 inch during the1920’s led him to the conclusion that the universe is expanding, and that an object’s recession velocityis proportional to its distance from the observer.
A deep image of an “empty”portion of the sky with the
Hubble Space Telescope
reveals that the universe is
filled with galaxies- many just
like our own. The light
we see from the most distant
galaxies has traveled approx-
imately 10 billion years to
reach us.
Deep Hubble Space Telescope Image
Using the Doppler Effect to Measure Velocity
Blueshift Redshift
Calcium
Magnesium
Sodium
Galaxy Spectrum
Stellar Spectrum
Spectra of a nearby star and a distant
galaxy
Star is nearby, approximately at rest
Galaxy is distant, traveling away from
us at 12,000 km/s
Galaxy Spectroscopy
Origin of the Universe -
Did It Begin with a Big Bang?
Penzias and Wilson, 1965 Arecibo Dish, Puerto Rico
Discovery of the Background Radiation from initial Big Bang
-Long wavelength
-came from all directions
Early History of the Universe
• Matter as we know it did not exist at the time of the Big Bang, only pure
energy. Within one second, the 4 fundamental forces were separated
– gravity - the attraction of one body toward another
– electromagnetic force - binds atoms into molecules, can be
transmitted by photons
– strong nuclear force - binds protons and neutrons together in the
nucleus
– weak nuclear force - breaks down an atom’s nucleus, producing radioactive decay
Early History of the Universe
• After 3 minutes, photons and neutrons began
to fuse to form the nuclei of hydrogen and
helium atoms
• About 300,000 years later, temperatures were
cool enough for complete hydrogen and
helium atoms to form
• Photons escaped from matter about the same
time, and light existed for the first time
Changing Composition of the
Universe
• 200 million years later, with expansion still occurring, stars and galaxies
began forming from leftover matter - hydrogen and helium
– nuclear fusion in stars has reduced the original composition of 100%
H and He to 98%
– when a dying star explodes, the heavier elements created by fusion
are blown into space to be recycled by newly forming stars
– the overall composition of the galaxies is gradually changing to the
heavier elements
The Solar System - Its Origin and Early Development
Our solar system, part of the Milky Way galaxy, consists of the Sun, nine planets, 64 known moons, many asteroids, millions of comets and meteorites, as well as interplanetary dust and gases
The Solar System - Its Origin and Early Development
General Characteristics of the
Solar System
• Planetary orbits and rotation
– planet and satellite orbits are in a common plane
– nearly all planet and satellite orbital and spin motions are in the same direction
– rotation axes of nearly all planets and satellites are roughly perpendicular to the plane of the ecliptic
General Characteristics of the
Solar System• Chemical and physical properties of the planets
– the terrestrial planets are small, have a high density, and are composed
of rock and metallic elements
– the Jovian planets are large, have a low density, and are composed of
gases and frozen compounds
• Slow rotation of the Sun
• Interplanetary material
– existence and location of asteroid
belt
– distribution of interplanetary dust
Meteorites -
Visitors from Outer Space
– Stones - composed of iron and magnesium silicates,
about 93% of all meteorites
– Irons - composed of iron and nickel alloys
– Stony-Irons - nearly equal amounts of iron and nickel
and silicate minerals
• Meteorites are believed to be pieces
of material that originated in the
formation of the Solar System about
4.6 billion years ago
• Size and Scale of the Universe
Size and Scale of the Universe
Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002
Size and Scale of the Universe
• Planet where we
all live
• Comprised
primarily of rock
• Spherical in shape
• 12,700 km in
diameter
• It would take 17
days to
circumnavigate the
globe driving a car
at 100 km/hr (62
mph)Image Credit: NASA/JPL/GSFC
19
20
EARTH
Mercury
Venus
Mars
21
22
Earth
Saturn
UranusNeptune
Jupiter
Pluto (not a planet) and its moon Charon
23
The Sun
is our nearest star
24
The Solar System
25
The Milky Way(Our Galaxy)
A hundred, thousand, million stars!
26
the Milky Way as seen from the Enterprise
A hundred thousand light years across
Light would take 100 000 years to travel across the galaxy.
27
Distances
• It takes 8 minutes for light to reach us from the Sun.
• A light-year is the distance travelled by light in 1 year.
• The Sun is our nearest star.
• Our next nearest star, Alpha Centauri is 4 light years away.
• The Milky Way is 100 000 light years across.
28
The local group of galaxies
Andromeda is the nearest biggalaxy to theMilky Way
Milky Way
29
Light from Andromeda takes
2 million years to reach us.
Milky Way
Andromeda
30
Local group
The Local Supercluster
Here the local group has shrunk to the size of the Milky Way in the last slide.
31
It left when the dinosaurs were on Earth.
Light from Virgo has taken 65 million years to
reach us.
Virgo Cluster
32
The Universe is mind-bogglingly big!
• The Sun is about 150 000 000 km away from
Earth
• Bright stars in the night sky are about 1000 000 (1
million) times as far away as the Sun.
• The near galaxies are about 100 000 times as far
away as the bright stars.
– 15 000 000 000 000 000 000 km
33 NASA
Size and Scale of the Universe
• The star that Earth
orbits
• Composed primarily of
hydrogen and helium
gas
• Uses nuclear fusion in
its core to generate heat
and light to allow itself
to resist the crushing
weight of its own mass
• Spherical in shape
• 1.39 Million km in
diameter
Image Credit: SOHO/NASA/ESA
Size and Scale of the Universe
• The Sun’s diameter is 109 times greater than
that of Earth
• Over 1 million Earths
would fit inside the
Sun’s volume
• The average distance
between the Earth
and the Sun is called
an Astronomical Unit
(AU) - it is about150
million kilometers
• It would take 11,780
Earths lined up side to
side to bridge the gap
between Earth and Sun
(or 107 Suns)Image Credit: SOHO/NASA/ESA
Size and Scale of the Universe
• 8 planets, several dwarf
planets, thousands of
asteroids, and trillions of
comets and meteoroids
• Mostly distributed in a flat
disk
• Pluto orbits ~40 AU from Sun• The Sun blows a constant
wind of charged gas into
interstellar space, called the
Solar Wind
• The boundary between the
Solar Wind and interstellar
space (the Heliosphere) is
Imag
e credit: N
AS
A
Imag
e cr
edit
: N
AS
A/J
PL
-Cal
tech
/R. H
urt
Imag
e credit: N
AS
A
Size and Scale of the Universe
• The region of the
Galaxy within about
20 light-years of the
Sun (40 light-years
diameter)
• A light-year is the
distance that light
travels in one year
(~10 trillion
kilometers or 63,000
AU)
• The neighborhood
stars generally move
with the Sun in its Image credit: Andrew Colvin
Size and Scale of the Universe
• The Milky Way Galaxy
is a giant disk of stars
100,000 light-years
across and 1,000 light-
years thick
• The Sun is located at the
edge of a spiral arm,
30,000 light-years from
the center
• It takes about 250
million years for the Sun
to complete one orbit
• There are over 200
billion stars in the Milky
Way
Image credit: R. Hurt (SSC), JPL-Caltech, NASA
Size and Scale of the Universe
• About 6.5 million
light-years in
diameter
• Contains 3 large
spiral galaxies --
Milky Way,
Andromeda(M31)
, and
Triangulum(M33)
-- plus a few
dozen dwarf
galaxies with
elliptical or
irregular shapes
• Gravitationally Image Credit: Andrew Colvin
Size and Scale of the Universe
• The Local
Supercluster is about
130 million light-
years across
• It’s a huge cluster of thousands upon
thousands of galaxies
• Largest cluster is the
Virgo cluster
containing well over
a thousand galaxies
• Clusters and groups
of galaxies are
gravitationally bound
together, however the
Image credit: Andrew Colvin
Size and Scale of the Universe
• Great walls and filaments
of galaxy clusters
surrounding voids
containing no galaxies
• Probably at least 100
billion galaxies in the
Universe
• Surveys of galaxies reveal
a web-like or honeycomb
structure to the Universe
Image Credit: Dr Chris Fluke, Centre for Astrophysics and Supercomputing,
Swinburne University of Technology
Image Credit: G.L. Bryan, M. L. Norman, UIUC, NCSA, GC3
• Computer simulations also show a
similar structure, often called the
“Cosmic Web”
Size and Scale of the Universe
Image Credit: Springer et al (2004)
• The Observable Universe is
currently about 91
billion light-years across
• There could be (and
likely is) much more
beyond that, but we
cannot see it from this
point in spacetime
• Note: The matter that
we can see glowing
shortly after the Big
Bang (detected by the
light it emitted 13.7
billion years ago) is
Most people have seen the curved Space-
Time figure, so let’s understand those!
The size of the Sun… Remember:Diagram shows the CURVATURE of Space-time
Draw the dent to be deepest is where the force is largest Where space is falling to the center “fastest”
Nothing to “See”43
44
How the Curvature Changes as we
Compress the SunWhat if we compressed the Sun
into a Neutron Star? Far outside the Sun
you can’t really tell the difference
• Force is the same
You can tell the
difference if you are
very close to the Sun
itself
• Force is bigger
The sun is now a few kilometers across
45
Compress the Sun into a Black Hole
Infinite curvature
Curvature is VERY different really close to where the mass
isNothing “curved” to SEE, deeper
just means where space
falling in fastest
Remember: The black hole is just a point in space
46
The Sun in Space-TimeThe size of the Sun…