Transcript aug27 - Astronomy

Astronomy 201
The Sun and its Planets
Dr. Jeff Kriessler
Discussion
Come up with as many examples of products
which are named after astronomical objects.
Discussion
Come up with as many examples of how
astronomy affects your daily life as you can.
Discussion
What is a day? How would you define it to
someone who doesn’t know anything about
how we keep time?
Time
Day – Time it takes the Sun to return to the
same position above the horizon.
Month – Time it takes the Moon to go
through its phases.
Year – Time it takes to move through the
seasons.
Note: Ancient definitions may differ from the modern
usage!
The hour
An hour originally was the time it takes the
Moon to move its own diameter against the
stars.
Today we define an hour as 3,600 seconds
where a second is 9,192,631,770 oscillations of
a Cesium-133 atom.
“Fixed” stars and Planets
Although the stars change their positions over
the course of a night and from night to night,
their relative positions (their positions relative
to each other) remain constant year after year.
Planet means “wanderer.” They change their
positions relative to that of the fixed stars
The Planets of antiquity
Sun
Moon
Mercury
Venus
Mars
Jupiter
Saturn
The days of the Week
Sunday – the Sun’s day
Monday – The Moon’s day
Tuesday – Tiw’s day – Mars
Wednesday – Woden’s day – Mercury
Thursday – Thor’s day – Jupiter
Friday – Freia’s day – Venus
Saturday – Saturn’s day
Ordering of the day names
Planets ordered by apparent length of
period of revolution about a presumed
stationary Earth:
Saturn
Jupiter
Mars
Sun
Venus
Mercury
Moon
Discussion
Assign each planet to an hour of the day:
Saturn 1, Jupiter 2, Mars 3, Sun 4, Venus 5,
Mercury 6, Moon 7, Saturn 8, Jupiter 9, …
Which planet gets assigned the 25 hour?
Southern circumpolar stars
Total Solar eclipse
Total Lunar Eclipse
Ptolemy explanation for
retrograde motion
Nicolaus Copernicus
Aristarchus explanation for
retrograde motion
Tyco Brahe
Johannes Kepler
Galileo Galilei
Isaac Newton
Atom
Ceres
HST image 1995
Cassini
Ceres
Our place in the Universe
Our Address:
Case Western University
Cleveland, Ohio
USA
Earth
The Solar System
The Milky Way Galaxy
The Local Group
The Local Supercluster
The visible Universe
Visible Universe
The portion of the Universe that light traveling
at 186,000 miles per second, has had enough
time to reach us. The visible Universe is a
sphere with a radius of about 14 billion light
years.
Hierarchy
Universe – made up of lots of galaxies
The Galaxies – made up of lot of solar
systems
The Solar System – where the influence of the
Sun dominates over the influence of other
stars