Ch 22 The Sun & It’s Solar System
http://www.brainpop.com/science
/space/sun/index.weml
I. Safe Methods for Studying
the Sun
1. Spectroscope
2. Solar Telescope
3. Satellites
1. Spectroscope
a. Chemical composition
b. Temperature
c. Internal Pressure
2. Solar Telescopes
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Projects a large image of the sun
into a dark underground room
Uses special glasses for viewing
Ex. Kitt Peak National
Observatory in AZ
3. Satellites
1. SOHO (Solar and Heliospheric
Observatory): Study Sun-Earth Connection,
launched in 1996
2. YOHKOH Spacecraft (designed to study
the Sun’s Corona, launched in 1991):
3. ULYSSES in a polar orbit over the sun
Solar Max to Solar Minimum
B. Properties of the Sun
1.
2.
3.
4.
Average size star
Diameter = 1,380,000 Km
Surface Temp = 55000C
Interior Temp = 15,000,0000C
C. The Sun’s Atmosphere
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3 Regions
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Photosphere
Chromosphere
Corona
1. Photosphere
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Apparent bright yellow
surface of the sun
Area of Sunspots
Made of Granules
 Granules- the tops of
individual columns of gases
 Gases rise from region below the
photosphere
2. Chromosphere
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Above Photosphere
Lower part of the outer atmosphere
Seen only during a solar eclipse
Colored Red by glowing Hydrogen
Radiates mostly X-rays & UV
Area of prominences
3. Corona
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Above Chromosphere
So sparse in gas it would be considered
a vacuum on Earth
Seen during a total solar eclipse as a
faint, pearly light
D. Solar Features
1. Sunspots- Dark, cooler areas on the
photosphere that occur in cycles
 Dark center called an umbra
 Lighter rim called penumbra
 Occur in pairs of opposite magnetic
charge, like a bar magnet
 Appear to move from left to right
across the photosphere
2. Solar Prominences

Huge loops of gas
that connect
different parts of
sunspot regions
3. Solar Flares
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Sudden eruption of heated
hydrogen & energy around
the area of a sunspot
(a prominence that has
exploded)
Directly correlated to sunspot # (#of
sunspots ,# of solar flares)
Source of Solar wind bursts
http://www.trschools.com/staff/g/cgirtain
/flare1.mpg
4. Solar Wind
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Constant stream of
electrically charged
particles coming
from the corona
Given off in all
directions
5. Coronal Holes
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Great tears in the Corona
May extend halfway around the sun
 Do not close for several months
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Source of solar winds
6. Auroras
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Northern Lights = Aurora Borealis
Particles of solar winds interacting with
Earth's Magnetic Field & upper
atmosphere
Mostly occur in Earth's polar regions
7. Magnetic Storms
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When particles thrown out by coronal
holes & solar flares are added to the
constant solar winds
Auroras may be seen at middle latitudes
Compasses may read incorrectly
Cellular & cordless telephone reception
may be interrupted
May interfere with radio frequencies
Sunspot
# increases
Sun Spots to Auroras
Solar Flares
increase
Solar Wind
bursts produced
Auroras
visible at poles
Magnetic Storms
occur
Auroras
visible at lower latitudes
E. Source of the Sun’s Energy
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E=mc2
Matter can be converted to energy &
vice versa
Fusion Reactions: Hydrogen that doesn’t
become Helium becomes Energy
5 Billion years of fuel left in the sun
Core is only place on sun where temp,
density & pressure are all great enough
to sustain nuclear fusion.
II. Observing the Solar System
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Solar System includes:
1. 8 Planets
2. Many Natural Satellites (moons)
3. Asteroids, Meteoroids, Comets
Solar System Cont’
4. All of the planets travel in elliptical orbits
(paths around the sun)
5. 5 planets can be seen without a telescope
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Mercury
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Venus
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Mars
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Jupiter
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Saturn
6. Meteors can also be seen
B. Planets & Stars
1.
2.
3.
Position of planets related to
constellations changes constantly
Planets move through the Ecliptic (path
through the Zodiac Constellations)
Most planets move eastward, night
after night through the sky
Retrograde Motion
C. Retrograde motion
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Apparent westward loop of a planet in
its path across the sky
Occurs because each planet travels
around the sun at different speeds
Planet appears to move backward when
the Earth overtakes it.
The more distant the planet is the
slower it changes
D. Solar System Models
1. Heliocentric Sun
centered model of
solar system
 Present day model
 Developed by
Copernicus (14731543)
2. Geocentric
Earth centered system
 Developed by Ptolemy 140 AD
a. epicycles- small orbit of a planet
b. deferent- large orbit of planets
around the Earth
III. Motions in the
Solar System
A.
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Tycho Brahe (1546-1601)
1st Long Term Sky Observations (20 years
worth)
Supported geocentric model
Believed Sun & Moon revolved around Earth
Thought other planets revolve around sun
Several versions, some have Earth rotating
Recognition of failure of Ptolemy's model
B. Johannes Kepler
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Inherited Tycho's work
Supported Heliocentric
Model
Designed 3 Laws of
Planetary Motion
3 Laws of
Planetary Motion
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1st Law - Planets travel in elliptical orbits
with the sun as the focus
a. Aphelion - pt. in planet's orbit
where it is furthest from the sun
b. Perihelion - pt. in planet's orbit
nearest the sun
2nd Law Equal Area Law
a. Speed of a planet around the sun is
not constant
b. Planets travel more rapidly when
closer to the sun
http://home.cvc.org/science/kepler.htm
http://www.sciencejoywagon.com/physicszone/les
son/03circ/keplers.htm
3rd Law is the Harmonic Law
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The time it takes a planet to travel one
orbit around the sun = its period
P2=D3
P is the period measured in years & D is
distance in AU (astronomical units)
The further a planet is from the sun,
the longer its revolution
C. Galileo
1. 1st Astronomer with a telescope
2. Drew craters he observed on
the surface of the moon
3. Discovered 4 largest moons of Jupiter
4. His findings supported the heliocentric
model of the solar system
D. Sir Isaac Newton
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Universal Law of Gravitation:
Change in Force = 1
d2
Gravity & Distance are inversely
correlated
Gravity & Mass are directly correlated
Newton’s Work
a. Force of gravity between any 2 objects is
related to the distance between the objects
& the masses of the two objects
b. Calculated the mass of planets from
dimensions of orbit
c. Thought tides were caused by force of
moon as it revolves around Earth
d. Used gravity to explain the long orbit of
comets & proved they are a part of the
solar system
VI. Other Objects in the Solar
System
A. Asteroids - large piece
of rock in space; largest
is Ceres, then Pallas
B. Escape Velocityminimum velocity
needed to escape the
gravitational pull of a
planet, moon, or
asteroid
http://www.spacewea
ther.com/
Scroll down for near
Earth misses
ASTEROID FLYBY
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On March 3rd,2003 a 25-meter wide asteroid,
2003 DW10, flew past Earth only 1.4 times
farther from our planet than the Moon. John
Rogers of the Camarillo Observatory
captured this image of the 17th magnitude
space rock on March 2nd. Rogers tracked the
asteroid, not the stars, so 2003 DW10
appears as a point-like speck in the middle of
the image. The surrounding stars are
streaked. [3D orbit] [ephemeris]
C. Kuiper Belt
 Vast disk of icy
comets starting
near Neptune’s
orbit
D. Comets
Composed of dust & rock particles
mixed in with frozen water, methane &
ammonia; most have very eccentric
orbits
Comet Hyakutake:
Photograph by M.Geyser.
Parts of a comet:
1. Coma - hazy, melting ice cloud around
the solid part of the comet
2. Nucleus - solid ball of the comet
3. Tail - formed by the solar winds
pushing away small melting particles;
always faces away from the sun
4. Ex. Halley’s, Encke’s, & Hale-Bopp
Comets
E. Meteoroids
- The small pieces of rock moving from
space; possibly left over from a fully
melted comet
F. Meteor - a meteoroid that burns up in
Earth’s atmosphere; glows as it is falling
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G. Meteorite 
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The part of a meteoroid that did not totally
burn up & strikes the Earth, sometimes
making a crater (Barringer Crater Az 25,000
yrs ago)
Antarctic ice caps have the most meteorites
Meteor craters are common on moons &
some planets, but not on Earth because:
1. atmosphere burns Meteors up
2. Earth is geologically active & weathering
occurs; erases some of the marks