Download AIM: What is Astronomy? Do Now:

AIM: What is Astronomy?
Do Now:
Answer the following question in your
notebook.
Where is the sun in our solar system?
What percent of our Solar System’s
mass is occupied by the Sun?
The sun makes up about 99% of our solar
systems mass.
I. Astronomy is the science that studies the universe
and all objects in it.
**Apparent motion= what an object appears to be
doing, not what it is actually doing**
Why do some
objects appear
to be moving in
space?
II. Two Views:
• Geocentric:
- Earth is motionless at the
center of the universe; all
planets including the sun revolve
around it.
• Heliocentric:
- Sun is the center of the solar
system; all planets revolve
around it. (Simple explanation)
Which one is true?
Heliocentric
III. Planetary Motion
- Johannes Kepler made observations of
objects in the night time sky. In doing this he
discovered that:
1. The path of each planet around the sun is
an ellipse (oval-shape), with the sun as one
focus.
- a focus is an object that a planet moves
around.
- Eccentricity measures the ellipse and
describes it’s shape.
Eccentricity = Distance between the foci
Length of the major axis
ESRT Cover
Major Axis
Focus 1
Focus 2
- Eccentricity can described a planets ellipse as:
• Eccentricity = 1
Most Eccentric
F
F
(a line)
• Eccentricity = 0.5
• Eccentricity = 0
(a circle)
Least Eccentric
From the back table take an Ellipse worksheet
from the top bin and a ruler
F
F
F
2. The closer a planet is to the Sun (foci)
the faster it revolves.
Faster
Slower
IV. Measurement in Space
• Astronomical unit (AU)
- it is about 150 million kilometers.
- is the average distance between Earth
and the sun.
• Light Year
- the distance light travels in one year.
V. Gravitational Force
• increases as distance between objects
decrease. (closer together = stronger force)
• increases as mass increases. (more mass =
more force)
In which diagram does the star have the greatest
gravitation force?
The
greatest
mass and
least
distance
VI. Other Motion:
• Retrograde Motion is the apparent
westward motion of planets as
compared to the background stars.
Closure:
- Obtain an “Intro to Astronomy”
worksheet (back top bin)
-Using your ESRT and the notes answer
the questions.
Eccentricity = Distance between the foci
Length of the major axis
Major Axis
Focus
1
Focus
2