Chapter 13: The Universe & Its Stars
Key Ideas – Chapter 13
1. Technology has advanced our understanding of
the universe
2. Nuclear fusion powers the stars & is the force
behind solar flares, prominences, sunspots &
solar wind
3. A star’s mass determines the stages of its life
cycle
4. Galaxies, star clusters, & nebulas can be
distinguished by their structures &
characteristics
Figure 2, P. 414
Visible Light Spectrum
1. Red = Long Wavelength at 4.3 – 4.6 x 1014 Hz
2. Blue = Short Wavelength at 6.0 – 6.7 x 1014 Hz
Boat Moving Through Water
& Making Waves
Figure 3, P. 414 & Figure 4, P. 415
Red Shift/Blue Shift
Star Light is ‘blue-shifted’
COBE DMR Image
Figure 7, P. 417
COBE Image
• COBE image shows
tiny variations in
cosmic background
radiation is a
remnant of the Big
Bang
Data From WMAP
Figure 8, P. 417
WMAP
• Data from the Wilkinson Microwave
Anisotropy Probe (WMAP) confirmed the age
of the universe is 13.7 billion years
• Warmer (red) and colder (blue) colours
represent different densities of matter in early
universe
Parallax
Figure 1, 2, & 3, P. 420-421
Baseline
Parallax
• In order to calculate how far away a star is, astronomers use a
method called parallax.
• Because of the Earth's revolution about the sun, near stars
seem to shift their position against the farther stars.
• This is called parallax shift.
• By observing the distance of the shift and knowing the
diameter of the Earth's orbit, astronomers are able to calculate
the parallax angle across the sky (using trigonometry)
Apparent/Absolute Magnitude
1. Different absolute
magnitudes of Light
5m
2. Same apparent
magnitude of light
5m
50 m
Nuclear Fusion
Figure 1, P. 425
Nuclear Fusion: required for a star to
be born
1. 2 protons create
deuterium
2. addition of a 3rd proton
creates helium-3
3. 2 helium-3 nuclei fuse to
form helium and release
 2 free protons along with
 considerable energy
Birth of a Star: Balancing Nuclear
Fusion & Gravity
1. Gravity pulls gas and dust inward
toward the core.
2. Inside the core, temperature
increases as gas atom collisions
increase.
3. Gas pressure & temperature
increases ignite nuclear fusion
4. Outward pressure from nuclear
fusion RESISTS the collapse of the
nebula. 6.
5. When gas pressure = gravity, the
protostar has reached equilibrium
Solar Anatomy
Solar Anatomy
Sun Spots: dark areas large
enough to swallow several Earths
Sun Spots
Sun’s Surface
• Gases move to the sides of the granule and sink
back into the Sun at the darker, cooler boundaries
of the granule (see Fig. 4 P. 427)
• The dark spots are called Sun Spots
Solar Flares & Solar Wind
Solar Flares:
• Brief explosions of large quantities of gas &
charged particles produced by changing
magnetic field lines around sun spots
Solar Prominences:
• Ionized gases form looping structures along
magnetic field lines lasting for weeks
Star Life and Death
NASA: HR Diagram Video
http://www.spacetelescope.org/videos/heic1017b/
http://www.universetoday.com/39974/hertzsprung-russell-diagram/
Above: well known stars in the Milky Way galaxy
Local Group of Gallaxies
Extending out 200 000 Light Years
• The Milky Way is
the central
player in a cast
of additional
smaller, irregular
galaxies and
other stellar
clusters that
remain within
the M.W. halo.
Here is a map of
some of these
objects:
http://rst.gsfc.nasa.gov/Sect20/A2a.html
Figure 3-6, P. 438
Classifying Galaxies: Hubble sequence
Edwin Hubble Classified galaxies according to
four basic shapes:
1.
2.
3.
4.
Elliptical Galaxies
Spiral Galaxies
Barred Galaxies
Irregular Galaxies
http://en.wikipedia.org/wiki/Galaxy_morphological_classification
What is at the Centre
of the Milky Way?
Sagittarius A*
• A supermassive black
hole, Sagittarius A*,
exists at the centre of
the core
• Mass of black hole = 2
000 000 Solar Masses
• Diameter of black hole =
15 times that of Sun
http://www.nasa.gov/centers/goddard/news/topstory/2008/blackhole_slumber.html
Globular Cluster
Open Cluster
1. Number of stars
Thousands - millions
A few hundred
2. Age of stars
All very old
Young stars
3. Shape and size of
cluster
Spherical, 10-30 light
years in diameter
Spread out, 30 light
years in diameter
4. Location in Galaxy
Near galactic centre
Only in the galactic disk
Dark Energy &
the Expansion of the Universe
Patricia Burchat: Shedding light on dark matter
http://www.ted.com/talks/patricia_burchat_leads_a_search_for_dark_energy.html
Dark Energy and Dark Matter
1. The more shallow the
curve, the faster the rate
of expansion.
2. Curve changes noticeably
about 7 billion years ago,
when objects in the
universe began flying
apart at a faster rate.
3. Astronomers theorize that the faster expansion rate
is due to a mysterious dark energy that is pulling
galaxies apart.
Image courtesy of NASA/STScI/Ann Field.