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Chapter 22
The Sun and Its
Solar System
Handy Dandy
Earth Science
Reference Tables
Page 15
HERTZSPRUNG-RUSSEL DIAGRAM
Properties of the Sun
• An average size yellow star
• fairly cool compared to other stars
• diameter is approx. 110 times larger
than Earth’s, with a volume that hold
more than 1,000,000 Earths. (yes,
that’s one million!!!)
• Light traveling from the sun takes
approx. 8 minutes 20 seconds to reach
Earth!
• surface temperature is approx. 5,500 C
and its interior temperature is believed
to be 15,000,000 C!!
Examine the sun at
different wavelengths
Sunspots & Prominences
• Sunspots are regions of intense
magnetic fields
• Sunspot temperatures are cooler
than photosphere, which makes
them appear as dark spots
• Prominences are regions along a
magnetic field line where conditions
are right for light to be emitted
• Huge, arching columns of gas often
appearing above sunspots
Solar Flares
• Occasionally, kinks and stresses
occur on magnetic field lines
discharging amounts of energy
(known as Solar Flares)
• The amount of energy released is
equivalent to a 2 billion megaton
bomb
• Flares release large numbers of
particles into the corona
Source of the Sun’s Energy
• The process of NUCLEAR FUSION
• Einstein explained this process as
E = MC² (matter can be converted into
energy)
• The hydrogen molecules that the sun is
made of fuse together to form a helium
atom. When this occurs, energy is given
off!
SUN – FUSION – atoms FUSE together
**It is estimated that the sun has enough
mass for nuclear fusion to continue for 5
billion more years!
3 Heliums
(atomic # 2)
fusing into 1
Carbon (atomic
#6) at the
core
Hydrogen
burning shell
energy
The Solar System
• All of the planets travel around the sun
in the same direction, but not at the
same speed
• Because of this, there may be times
when Earth passes a planet in its orbit
• The planet will then appear to be moving
in the opposite direction (backward)
• This is called retrograde motion
– The planet is not really moving backward
(think about two cars traveling side by
side…when one car speeds up, the other car
may appear to move backward)
Retrograde Motion Animation
Retrograde Motion Animation
Solar System Models
• Geocentric (Geo=Earth) – ancient people
believed that the Earth was the center
of the universe, and all planets and stars
moved in orbits around Earth (remember,
the sun appears to rise and set each day
when it is really the Earth spinning that
causes this)
• Heliocentric (Helio = Sun) – this is the
accepted model. It states that the sun
is the center of the solar system, and
all of the planets move around the sun
Geocentric Model
• The Geocentric Model remained the
accepted theory of the orientation of
the universe for so long because all
celestial movements (including retrograde
motion, stars, sun, moon, comets, etc.
could be explained via a Geocentric
model. The only motion that can’t be
explained by a Geocentric model is
Foucault’s Pendulum - because in the
Geocentric Model – THE EARTH DOES
NOT ROTATE!!!!!!!!
• (MORE ON Foucault’s Pendulum later…)
Kepler’s 3 Laws of
Planetary Motion
First Law – Elliptical Orbits
• All planets travel around the sun in an
elliptical orbit (LAB) with the sun as one
of the foci
• Because the orbits are not perfectly
circular, the distance between the sun
and the planet changes
• Eccentricity is a measure of how
stretched out the planet’s orbit is (Ref.
Tables P. 1, LAB)
0.0
.25
.50
.75
.90
Formula – Page 1 of ESRT’s
eccentricity = dist. between foci
length of major
axis
These measurements are made in cm, m or km – and are
either provided to you or you measure them on a paper
drawing of the elliptical orbit….
VIF
• Even though the planet shapes are
mathematically elliptical, all of the
planets orbits (except for Mercury
eccentricity = 0.206 &
Pluto – eccentricity = 0.250) appear
to be perfect circles when looking
at their orbital shapes from space
or when drawing them on paper…
Second Law – Equal Area
• When the planets are closest to the sun
they move faster, and when they are
farthest from the sun they move slower
• Because of this, 2 imaginary triangles
drawn between the sun and the planet at
two points in the planet’s orbit that
cover any 2 equal lengths of time would
cover an equal amount of area
• HUH??????????? You say
• …here are some examples….
Here’s an illustration…
Third Law – Harmonic Law
• the farther a planet is from the
sun, the longer its period of
revolution (the longer it takes to go
around the sun – common sense)
– #1 – it goes slower
– #2 – it has further to go (DUH!!!)
• Kepler stated this using the formula
P² = D³, where P is the period of
revolution (in Earth years) and D is
the distance from the sun (in AU’s)
PS – This is how the planet Mercury was
named…Mercury was the Messenger of the Gods and
is the guy with the wings on his feet…he was fast…
ETC…
VIF - Aphelion & Perihelion
• When a planet is closest to the sun it
is called perihelion, when it is farthest
from the sun it is called aphelion (think
Aphelion = Away)
• Earth’s perihelion is Jan. 4th-ish –
after the first day of Winter, and
Earth’s aphelion is July 4th-ish – after
the first day of Summer. The
Solstices and Aphelion/Perihelion DO
NOT JIBE!!!!!
Disclaimer – this illustration is EXTRMEMELY
EXAGGERATED!!!!!!!!!!!!!!!
Newton’s Universal Law of
Gravitation
• the force of gravity between any two
objects is directly related to the masses
of the two objects, but inversely related
to the square of the distance between the
centers of the two objects
F = force of gravity between 1 and 2
F = Gm1m2
r2
G= Gravitational Constant (9.8 m/s2)
r = distance between objects
m = masses of objects
Simplified:
• The larger the objects, the
greater the force of
gravity between them
• Also, the greater the
distance between the two
objects, the less the force
of gravity pulls on them
Here we have vector
addition…wait ‘til
Physics!!! 