1. The Solar System

2. The Solar System Early Astronomy
Astronomy- the science that studies the universe
It Investigates: properties of objects in space, and the laws under which they function.
Geocentric Model
Earth was a motionless sphere around
which the rest of the universe revolved

3. The Solar System
In A.D. 141, Ptolemy presented an advanced geocentric model of the universe that we now call the Ptolemaic System.
The precision with
which it predicted
the motions of the
planets, allowed it
to go unchallenged for
almost 13 centuries
Epicycle- small circle
each planet moved on
Deferent- larger circle that
the epicycle is centered
on and moves around
Earth

4. The Solar System
The Catholic Church controlled scientific thought (if they controlled scientific thought, they had more power) during this time period and anyone not believing in a geocentric model of the universe was punished
Biblical passages suggest the Sun is in constant motion while the Earth remains in one place
It was thought that the creation of the planets occurred after the creation of Earth
The development of modern astronomy was a break from previous philosophy and religious views.
Scientists began to realize that the universe, and everything in it, was governed by natural laws.

5. The Solar System 1543 here comes Copernicus
Heliocentric Model (sun at center)
1543 here comes Copernicus
**actually Copernicus was not the first to suggest the heliocentric model but further developed and it eventually gained popularity
Copernicus believed
the sun was at the
center of the solar
system and was able
to work out the
arrangement of the
known planets

6. The Solar System
Johannes Kepler (late 1500’s)
The path of each planet around the sun is an ellipse– oval shape
When he used circular orbits his calculations did not fit observations
More on this after Galileo 

7. The Solar System Galileo 1610 builds a telescope, discovers:
Moons around Jupiter
Proved not everything
in the sky revolves
around the Earth
Venus goes through
series of phases similar
to the moon’s
Not possible if both it
and the Sun circled the
Earth

8. The Solar System Now back to Johannes Kepler and ellipse…
The path of each planet around the sun is an ellipse (oval-shape) with the sun at one focus and an imaginary point at the other
Eccentricity- a measure of how round or flat (oval) a shape is
Eccentricity = Distance between foci **has no units
Length of the major axis
   

9. The Solar System

10. The Solar System Why is eccentricity important?
All planets revolve around the Sun (one foci) along an elliptical path called an orbit
For all planets in our solar system, one of the two foci is always the sun
Planets revolve
around the sun at
varying speeds.
The closer the
planet to the sun,
the fast the speed

11. The Solar System
Perihelion - the point in the orbit of a planet, at which it is closest to the sun
Planets at perihelion travel faster here due to the greater gravitational attraction between the objects
Aphelion – the point in the orbit of a planet at which it is farthest from the sun
Planets at aphelion travel slower here due to less gravitational attraction
WHY IS THIS TRUE?

12. The Solar System

13. The Solar System The Solar System (SS)—Basic info
Scientists think the SS formed about 4.6 billion years ago from a cloud of hydrogen, helium, rock ice and other materials pulled together by gravity
Part of the milky way galaxy (galaxy = billions
of starts held together by gravity) which is a
spiral galaxy
Consists of the sun, the planets, their moons,
and a variety of smaller objects
Sun is at the center
Gravity holds the solar system together
Distances in the SS
Astronomical Unit (AU)- equal to the average distance between the sun and Earth
About 150,000 km (93, 205 miles)
SS extends more than 100,000 AU from the sun
The Sun
99.85% of the mass of the solar system is contained within the sun
Mid sized star-half way though its life cycle
The Planets
An object that orbits a star, is large enough to have become rounded due to its own gravity, and has cleared the area of its orbit Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, **Pluto
Dwarf Planets
An object that orbits the sun and is spherical but has not cleared the area of its orbit
Pluto was considered the 9th planet of solar system but shares the area of its orbit with other objects so is now considered a dwarf planetS
Satellites
An object that orbits a planet, moons, except Mercury and Venus, every planet in the SS has at least natural satellite or moon
Smaller Object
Asteroids - small rock bodies that orbit the sun
Comets- loose spheres of ice and rock that have very long narrow orbit

14. The Solar System
In case you didn’t know….

15. The Solar System Terrestrial (Inner) Planets Small Dense Rocky surface
In order from closest – farthest
from sun
Mercury
Smallest
Closest to sun
Virtually no atmosphere
Venus
Thick atmosphere, always
cloudy, greenhouse effect
Hottest surface of any planet
Unusual pattern of rotation,
8 months to rotate once
and 7.5 months to revolve once
Rotates from East to West

16. The Solar System Earth Mars The water planet- Liquid
water covers about 70% of
surface
Suitable temperature range for
most living things to survive
Atmosphere rich in O2, N, CO2,
greenhouse effect
One moon
Mars
The red planet
Too cold for liquid water now,
had liquid water in the past
Has water ice now
Atmosphere is 95% CO2
Two moons

17. The Solar System ***Between mars and Jupiter there is an asteroid belt
Gas or Jovian (Outer) Planets
Called “gas giants”
Large
Less Dense
Do not have solid surfaces
Strong gravitational force which keeps gas from escaping
Thick atmospheres
Much of the material that makes up these planets is liquid because the pressure inside these planets is so high
Have many moons
Surrounded by rings- thin disk of small particles of ice and rock

18. The Solar System In order from closest – farthest from sun Jupiter
Largest and most massive
planet
Thick atmosphere of
hydrogen and helium
At least 63 moons
Saturn
2nd largest planet in SS
Rings made up of chunks of
ice and rock each traveling
in its own orbit around Saturn
At least 61

19. The Solar System Uranus Neptune Pluto– dwarf planet Very cold
Methane in atmosphere (give it
blue color)
Surrounded by thin flat rings
Axis of rotation is about 90o to
vertical, rotates from top to bottom
instead of from side to side
At least 27 moons
Neptune
Cold, blue planet
Atmosphere contains clouds
At least 13 moons
Pluto– dwarf planet
Does not clear the neighborhood of its
orbit
Highly elliptical orbit
Perihelion distance = 4440 million km from sun
Aphelion distance = 7380 million km from sun