Download Stars, Galaxies, and the Universe

Chapter 21
Stars, Galaxies, & The Universe
Telescopes
Characteristics of Stars
 Electromagnetic Radiation
 Forms of Radiation
 The Electromagnetic
Spectrum
 Types of Telescopes
 Refracting Telescopes
 Reflecting Telescopes
 Radio Telescopes
 Other Telescopes
 Observatories
 Advanced Telescopes
 Telescopes in Space
 Classifying Stars
 Color and Temperature
 Size
 Chemical Composition
 Brightness of Stars
 Apparent Brightness
 Absolute Brightness
 Measuring Distances to Stars
 The Light-Year
 Parallax
 Parallax in Astronomy
 The Hertzsprung-Russell
Diagram
Stars, Galaxies, & The Universe
Lives of Stars
Star Systems and Galaxies
 The Lives of Stars
 A Star is Born
 Lifetimes of Stars
 Deaths of Stars
 White Dwarfs
 Supernovas
 Neutron Stars
 Black Holes
 Star Systems and Clusters
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Multiple Star Systems
Eclipsing Binaries
Planets Around Other Stars
Star Clusters
 Galaxies
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Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies
Quasars
 The Milky Way
 The Scale of the Universe
 Scientific Notation
 The Immensity of Space
Stars, Galaxies, & The Universe
The Expanding Universe
 How the Universe Formed
 Moving Galaxies
 Cosmic Background
Radiation
 Age of the Universe
 Formation of the Solar
System
 The Solar Nebula
 Planetesimals
 The Inner Planets
 The Outer Planets
 The Future of the Universe
 Dark Matter
 An Accelerating Expansion
How does distance affect an
image?
 Telescope- device that makes an object in
the sky appear closer.
 Revolutionized astronomy (study of
space)- allowed them to see objects in
space for first time.
 Galileo made telescope famous seeing sun
spots, Saturn’s rings, and Jupiter’s moons
Electromagnetic Radiation
 There are waves of energy and light
moving around us in the form of TV and
radio transmissions, gamma radiation from
space, and heat in the atmosphere.
 The waves of energy are called
electromagnetic (EM) because they have
both electric and magnetic characteristics.
Electromagnetic Radiation
 They are classified by the frequency of
their wavelength, going from high to low
frequency.
 When a wave has a lot of energy, it could
be a gamma ray or x-ray, and has high
frequency.
 If it has low frequency, it has less energy
and could be a TV or radio wave.
 http://video.pbs.org/video/2219781967/
REFRACTING TELESCOPES
REFLECTING TELESCOPES
OBSERVATORIES
DETECTING ENERGY
 All types of EM radiation are useful to the
world of science. Radio waves for example,
They are used to carry communications from
one point to another.
 Astronomers listen to the radio waves of
other galaxies to learn more about their stars.
 Stars give off large amounts of EM radiation
across the entire spectrum and we can study
that radiation to learn more about the
universe.
Classifying Stars
 Color
 Temperature
 Size
 Composition
 Brightness
Star Properties

Color & temperature
 white / Hot stars
 Blue
 Yellow, orange,
 red / Cool stars
Star Properties

Size
 neutron- smallest
 white dwarf
 medium
 large
 giant/ super giant
Star Properties
 Composition
 Use a spectrograph (breaks light into
colors and produces an image) to detect
elements
 Gases in a star’s atmosphere absorb some
of the wavelength of the light it produces
 Each Chemical element absorbs light
Light-year
 The distance between stars and
galaxies in the universe is so vast it
would be too much to describe it in
miles or kilometers—like measuring
the distance from New York to Tokyo
in inches! Instead, scientists use
light-years to measure distances in
space.
Light-year
 is actually a distance: the distance
that light travels in one year.
 Light travels 186,000 miles per
second which is equal to 300,000
km/s
 9.5 trillion km/year
 Brightness
 How a star appears from Earth
depends on the distance and the
actual brightness of the star
 Actual brightness depends on size
and temperature (absolute)
 Distance depends on how bright it
appears (apparent)
Star Magnitude (Brightness)
 Two types of magnitude
 Absolute
 Apparent
Apparent magnitude brightness
 Measure of the amount of light
received on Earth from a star.
 Brightness seen from Earth
 Both apparent and received have a r
Absolute Magnitude Brightness
 The brightness the star would have at
a standard distance from Earth.
 The total measure of the amount of
light given off by a star.
 Total= absolute
Space Measurement
 Scientists can measure the parallax of
relatively close stars to determine their
distance from Earth.
 Knowing the angle that the star’s
position changes and the size of the
Earth’s orbit, we can calculate the
distance of the star from Earth.
Space Measurement
 Parallax- the apparent shift or change
in position of an object when you look
from 2 different positions
 Seen if you look at a star when Earth is
at two different points during its orbit
around the sun
 if you stretch out your hand in front of you and
look at your thumb while taking turns covering
one eye and then the other, your thumb will
appear to move back and forth.
 Stars do the same thing, but our eyes are much
too close to see the difference.
 If we take a picture while on one side of Earth's
orbit, and then take another when we get to
the opposite side of the orbit, then we have a
large enough distance that we can see the stars
parallax, and determine how far away they
really are.
Parallax
Classifying Stars
 Ejnar Hertzsprung and Henry Russell
graphed stars by temperature and
absolute magnitude in a H-R diagram
 Main
Sequence
 Dwarfs
 Giants
 (Pg
722)
Main sequence stars
 90% fall on the diagonal band of the H-R
diagram
 Stars in upper left of diagram graphs the
hot, blue, bright stars
 Stars in lower right are cool, red, dim stars
 Stars in the middle are average, yellow stars
like our sun
Dwarfs and giants
 The 10% that fall outside the diagonal of the
main sequence stars are dwarfs and giants
Fusion
 The fusion of hydrogen in the core of
star releases huge amounts of
energy- atoms combine to form
heavier atoms
(2) HYDROGEN ATOMS SMASH and FUSE into HELIUM with a RELEASE of ENERGY
A Star is Born
 All stars begin as a
nebula (large cloud
of gas and dust
spread out in large
volume)
Nebula
 A nebula is a cloud of dust and gas, composed
primarily of hydrogen (97%) and helium (3%). Within
a nebula, there are varying regions when gravity causes
this dust and gas to “clump” together. As these
“clumps” gather more atoms (mass), their gravitational
attraction to other atoms increases, pulling more
atoms into the “clump.”
Protostar
 Protostar- a
contracting cloud of
dust with enough
mass to start
formation of a starfusion has not
begun
A star is born when the
contracting gas and dust from a
nebula become so dense and
hot that nuclear fusion begins.
The evolution of low mass stars
• Contracts and
breaks apart
instability
caused by
gravity
• Temperatures
increase,
particles get
closer together
• Fusion begins
Nebula
New Star
• Heat causes
pressure that
balances the
attraction due to
gravity
• Becomes a main
sequence star
• Continues to use
hydrogen fuel
• Hydrogen in core
depleted
• Core contracts and
temperature inside
increases
• Outer layers cool
Giant/White
Dwarf
• Core uses helium
outer layers escape
into space
• Leaves behind hot
dense core now white
dwarf
High Mass Stars
Black hole
Nebula
form when
supernova
Recycling Matter
collapses to
a point
where no
Neutron Star
volume
or Black Hole
Main
sequence
Core heats up
quickly
Supernova
Supergiant
Black Holes
http://coolcosmos.ipac.caltech.edu//cosmic_kids/AskKids/blackholes.shtml
Clusters of stars
 Open
 Globular
 Open- loose,
disorganized
appearance
containing no more
than 1000 stars
 Globular- large
groupings of older
stars. Round and
densely packed
with stars. Some
may contain more
than a million stars
Galaxies
 enormous swarms of stars, dust, gas, and
dark matter held together by gravity.
 The sun is one of about 100 billion stars in
our own galaxy, called the Milky Way. If
you think that’s incredible, imagine this:
The Milky Way is just one of billions in the
observable universe!
Spiral
 Spiral galaxies are shaped like disks and
look like pinwheels from above. Young
stars are found in the arms, and older stars
are found in the central bulge, or nucleus
Elliptical galaxies
 Elliptical galaxies are the oldest and
largest galaxies. They are smooth and oval
and contain many old stars. There are
many more elliptical galaxies in the
universe than spiral galaxies
Irregular galaxies
 Irregular galaxies don’t have a distinct
shape and are not symmetrical like spiral
or elliptical galaxies. They may be young
galaxies that have not yet formed a
symmetrical shape, or their irregular shape
may be caused by two galaxies colliding.
The Universe within 50000 Light Years
The Milky Way Galaxy
 Clusters of galaxies are often
collected in super clusters.
 Our Milky Way is part of the Local
Group and is part of the Virgo Super
cluster, which contains several
thousand galaxies.
Milky Way Galaxy
 Classified as a
 About 100,000
normal spiral
galaxy
 Contains more
than 200 billion
stars
light years wide
 Sun orbits
galaxy’s core every
240 million years
Other planets around other stars?
 http://www.nasa.gov/multimedia/videogallery/index.ht
ml?media_id=58885371
Origins of the Universe
 How did the
Universe begin?
Where did we all
come from? Has
the Universe
always been the
same? Does the
Universe change?
Steady State Theory
 One theory is the
Steady State Theory
 The universe has always
been the same and will
always stay the same
 Evidence suggests that
this is not true thoughindication are the
universe was very
different in the past.
Oscillating Model
 A second idea is the Oscillating Model of
the Universe.
 An expansion of the Universe began and
everything moved outward.
 Over time, expansion slowed and the matter
contracted back in.
 Process repeats itself over and over
 Works like a slinky
Big Bang Theory
 Scientists accept this theory as more likely.
 We know the universe is expanding
outwards
 About 12-15 billion years ago a giant
explosion occurred
 The universe began to expand
Big Bang Theory
 Within a fraction of a second, the universe
grew from the size of a pinhead to 2000
times the size of the sun
 By the time the universe was one second old,
it was a dense swirling mass of particles.
 Matter began to clump together, hydrogen
and helium formed
Big Bang Theory
 More than a billion years after the first
explosion, the first stars were born.
Origin of Universe
 Steady state theory
 Proposed the universe
has always existed the
same as it is now
 Oscillating model
 Universe began with
expansion occurring in
all areas of universeexpansion slowed,
matter contracted, and
process began again.
 Big Bang Theory
 The universe began
with an enormous
explosion.
Our Expanding Universe
 The Doppler Shift explains how we know the
Universe is expanding.
 If a star is moving towards Earth, the light
wavelengths are compressed and you would
see the spectrum in blue
 If a star is moving away from Earth, the light
wavelengths are stretched out and you see
the spectrum in red.
The Red Shift- Hubble Law
 In 1929, Edwin Hubble
published a paper about
light from other galaxies.
 All galaxies beyond the
Local Group (our group of
galaxies) show a red shift in
their spectrum, this shows
they are moving away from
us. The Universe is
expanding…….
Dark energy
 In the late 1990’s astronomers observed the
expansion of the universe appeared to be
accelerating.
 Galaxies seemed to be moving apart at a
faster rate now than in the past.
 No know force to account for it which they
now call dark energy.
 http://hubblesite.org/hubble_discoveries/dark_energy
/
Looking Back in Time
EXPLAIN THIS!!!!!!!!!