Transcript chapter 28 pages 747-752

Diff Geo Unit 4
Chapter 28 pages 747-752, chapter 29
pages 793-795, chapter 30 pages 813827, and chapter 31 pages 839-851
CHAPTER 28
PAGES 747-752
Radiation
• Light travels in the form of electromagnetic
radiation
• We see only visible light.
• Electromagnetic radiation is measured by
wavelength.
• Shorter the wavelength, the stronger the
radiation.
Electromagnetic Spectrum
Telescopes
• A telescope collects light.
• 2 types we use:
• 1. refracting telescopes use lenses to focus
visible light
• 2. reflecting telescopes use mirrors
• Most of our telescopes are reflectors.
• Interferometry is linking telescopes together
to act as one
• We’ve explored space with satellites and sent
man into space on spacecraft.
• NASA technology has been passed onto
commercial industries for common use
• This is called spinoff
CHAPTER 29
PAGES 793-795
Formation of solar system
• 1. Interstellar cloud of gas (hydrogen and
helium) and dust
• 2. Due to gravity, condensing began and
concentrated the mass in areas
• 3. Rotation increased as condensed areas
gained mass and formed a disk shape
• 4. The sun formed from the center of this
nebula
• 5. Areas around the sun cooled, more so
further away
• 6. Substances formed in both liquid and solid
form depending on their distance from the
sun
• 7. Accumulation of condensed particles
formed planetessimals
• 8. Planetessimals merged to form planets,
asteroids are the pieces leftover
CHAPTER 30
PAGES 813-827
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The sun gets its energy from hydrogen fusion.
H + H --> He
The sun is 70% H and 28% He
The sun has two zones:
1. Radiative zone comes out from the center
2. Convective zone on the surface
3 Types of Spectrum
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1. Continuous- has no breaks in it
2. Absorption- dark bands within
Caused by a cooler gas in front of the source
3. Emission- all dark with colored bands at
certain wavelengths
Constellations
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Groups of stars
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Appear to move around the north pole
Groups of stars gravitationally bound to each
other called clusters
• Two stars gravitationally bound to each other
called binary stars.
Position and Distance
• 1 light year = 9.41 x 10^12 km
• Parallax- the apparent shift in positions of a
star because the observer is the one moving
• The Earth orbits the Sun, so stars look like
their moving
Properties of Stars
• Magnitude- how bright it appears
• Apparent magnitude- The brighter it looks
from Earth, the more negative it’s #
• Absolute magnitude- how bright the star is
from 10 parsecs
• Luminosity- measure of the star’s energy
output
• The star’s mass determines its temp,
luminosity, and size/diameter
Spectra
OBAFGKM
Oh be a fine guy/gal, kiss me!
• O is the hottest
• M is the coolest
• The sun is a G2 star
Shifting of spectral lines
• When a star’s spectra is shifting to different
wavelengths, this means it is moving
• If the spectra shifts towards the blue (shorter)
wavelengths, the star is moving towards us
• If it shift towards the red (longer)
wavelengths, then the star is moving away
HR Diagram
• Plots absolute magnitude (Y axis)
• Plots Spectral Type (X axis)
• What does that really mean?
• The X axis is the temp (hotter, left and cooler,
right)
• The Y axis is how bright it is (brightest, top and
dimmest, bottom)
Star Life Cycle
• 1. nebula- cloud of gas and dust
• 2. Rotation causes formation of protostar
• 3. Once it is hot enough for H to fuse into He,
main sequence stage occurs
• This is the longest stage of a stars life.
• 4. In medium sized stars, once all H has been
fused into He, He then starts to fuse into C
during the Red Giant stage
• 5. Once it’s used up all the He in its core, then
the star shrinks and becomes a white dwarf
• 6. Later as it continues to die, it will become a
black dwarf
Large Stars
• After the main sequence stage, these stars will
undergo a supernova
• After this, they could either form a neutron
star after everything collapses or a REALLY
large star will become a black hole
• Both are extremely dense
CHAPTER 31
PAGES 839-851
The Milky Way Galaxy
• Spiral shape
• Bulge surrounded by a halo of spiral arms
Other types of galaxies
• Elliptical
• Divided into subclasses based on apparent
ratio of their major and minor axes
• Irregular
• No distinct shape
• Most galaxies are clustered into groups
Is the universe expanding?
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Hubble says yes
V=Hd
V= speed
H= Hubble’s constant
H= 70 km/s/mparsec
D= distance in mega parsecs
The greater the distance, the faster its moving
away.
Big Bang Theory
• The universe began as a point, expansion
occurred, and has been expanding ever since
• Evidence:
• Cosmic (microwave) background radiation
• Quasars
• Red shift
Evidence #1
• Cosmic (microwave) background radiation
detected by antennae in 1965 coming from all
directions in space
• The emitter of this radiation has a
temperature of that predicted by the big bang
theory
• Therefore scientists interpret this to be
coming from the beginning of the big bang
Evidence #2
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Quasars
Most stars are not strong radio emitters
Quasars are, and were discovered in the 1960s
Quasars emit spectra lines of common elements with
longer wavelengths ex: H
• The redshift of quasars is much longer than any
other galaxy, which means they are the farthest away
• This associates them with the timing of the big bang
Evidence #3
• Red shift
• Edwin Hubble saw that galaxies are moving
away from earth based on the red shifts he
saw in 1929
• In a medium that is uniformly expanding, all
points are moving away from all other points,
and no point has to be at the center
Will the expansion of the universe
stop?
• Competition between outward momentum of
the expansion of the universe and the inward
force of gravity
• Density is higher than critical density= closed
universe
• Density is lower than critical density= open
universe
• If they equal each other, the universe is flat.
• Astronomers have discovered that the rate of
expansion is speeding up
• The only explanation offered so far is that a
previously unknown force is acting to push the
galaxies apart
• This unknown force is dominating over gravity