all about astronomy

1. ASTRONOMY
SCIENCE THAT STUDIES THE
UNIVERSE

2. WHERE DOES THE
EARTH FIT IN THE
UNIVERSE?
• The Universe is everything. All the planets, stars, comets, moons, empty
space, gas clouds, nebulas and anything that exists.
• Within the Universe there exists many Galaxies, or groups of stars that
travel through space . Within a Galaxy are many solar systems.
• The Earth is part of the Universe, as is our star, the sun, and all the other
planets, moons and other heavenly bodies we call our solar system. A
solar system consists of a star and the heavenly bodies revolving around
it.
• Within a galaxy, there are billions of stars and solar systems. We are part
of one galaxy, the Milky Way Galaxy. There are billions of other galaxies

3. WHERE DID THE UNIVERSE COME
FROM?
• BIG BANG THEORY – States that at one time the entire universe was
confined to a dense, hot, supermassive ball. Then about 13.7 billion years
ago, a violent explosion occurred, hurling this material in all directions.
This is the most widely accepted scientific view of the universe as we
now know it.
• SHOW UNIVERSE VIDEO ON THE BIG BANG THEORY AFTER THE CLASS
DEBATE – The video gives an excellent discussion on the competing
theories of the Big Bang Theory, such as the Steady State theory.
• CLASSROOM DEBATE – Students will be broken down into four groups,
with each group conducting computer research on a present or past
theory. The Big Bang Theory, The Steady State Theory and the Inflation
Theory will be used. The fourth group will judge the debate and assign
points to determine a winner. Debate Rubric will be provided for the
judges to use. Debate guidelines for groups provided separately.

4. SO WHERE DID OUR SOLAR SYSTEM
COME FROM?
• The current theory is called the Nebular
Hypothesis. The theory states our sun formed
from a huge rotating cloud of space gas and
dust called a nebula.
• After the sun formed, the left over materials
from the cloud started to revolve around the
newly formed sun. Over millions of years
planets formed as did moons around the
planets.
• Nebulas still exist today and photographs taken
by space telescopes such as the Hubble of many
of these Nebulas are available for viewing over
the internet.
• PORTABLE LAB VIEWING OF
NEBULAS WITH SOURCES.

5. ANCIENT ASTRONOMERS
• ARISTOTLE – Believed the Earth was
round because he saw during lunar
eclipses the Earth cast a round
shadow on the moon.
• ERATOSTHENES – Established the
size of the Earth within a reasonable
amount.
• HIPPARCHUS – Created a star
catalog of over 850 stars.
Determined the length of a year.
Developed a method to predict
• ARISTOTLE
• ERATOSTHENES

6. WHAT IS SO SPECIAL ABOUT THEM?
• The common thought at this
ti
me was that the Earth
was
fl
at and was the center of the universe.
• All of these astronomers lived over 2000 years ago.
• The Roman Catholic church was extremely powerful
then and any talk that was not along the earth-
centered way of thinking was quickly discouraged.
• Any one who persisted was subject to arrest and
worse. This discouraged new views from being
pursued for hundreds of years.

7. Models of the Universe
• GEOCENTRIC MODEL – The belief that
the Earth was the center of the universe
and that every other body revolved
around the Earth. The only known
planets were Mercury, Venus, Mars and
Saturn.
• HELIOCENTRIC MODEL – The belief that
the sun is the center and everything
revolves around the sun. First proposed
by ARISTARCHUS, 312 – 230 BC.
• These two models were debated upon
by scien
ti
sts but most believed the
Geocentric model was correct for
hundreds of years.
• GEOCENTRIC MODEL
• HELIOCENTRIC MODEL

8. PTOLEMAIC SYSTEM
• Claudius Ptolemy, AD 141, published
a 13 volume work describing the
mo
ti
on of the planets. Ptolemy used
a Geocentric Model of the Universe
for his work, which was wrong, but
it was considered the de
fi
ni
ti
ve
work on astronomy for the next
1300 years. It was not un
ti
l the
1400’s that his beliefs were
ques
ti
oned and disproven. Even
then, the church s
ti
ll had the power
to regulate what was taught and
they believed the Geocentric
version.

9. NEW THEORIES EMERGE
• COPERNICUS, 1473-1543, was the
fi
rst to go back to the Heliocentric
model that Aristarchus proposed 1100 years earlier.
• TYCHO BRAHE, 1546-1601, followed suit and made more precise
observa
ti
ons about the universe than anyone had ever done before.
• JOHANNES KEPLER, 1571-1630, determined the planets rotate around
the sun in an ellipse, or egg shaped pa
tt
ern instead of a circle. Kepler
also devised the 3 laws of planetary mo
ti
on that are s
ti
ll used today.
• COPERNICUS
• TYCHO BRAHE • JOHANNES KEPLER

10. GALILEO GALILEI
The work of Galileo Galilei changed
our view of the universe and our
solar system forever. Living from
1564 to 1642, his study and
descriptions of the movement of
heavenly bodies were aided by the
use of the telescope for the first
time in Astronomy. Galileo
actually built his own telescope
after obtaining the design from the
inventor of the first telescope.
His was a simple homemade version
made from parts he made himself
that only magnified objects about
30 times but that magnification
enabled him to see things never
before seen by man. His thoughts
and writings on the subject was in
direct contrast to the church views
believed by the masses. For this,
Galileo paid a heavy price.

11. Galileo
• From his discoveries, Galileo actually proved the Earth was not the center of the
Universe or the even the center of the Solar System. His most important discoveries
are listed:
• 1. Galileo was the
fi
rst to discover that Jupiter has moons that revolve around it,
thus proving not everything revolves around the Earth, meaning the earth is not the
center of the solar system.
• 2. Discovered Venus goes through phases like our moon. This means that Venus
revolves around the sun, not the Earth.
• 3. Discovered that planets are circular discs and not just points of light meaning they
are Earth-like.
Galileo’s 2nd discovery that Venus
goes threw phases like our moon
Galileo’s 3rd discovery that planets
are circular discs and not just points
of light
Galileo’s 1st discovery that Jupiter
has moons that revolve around it

12. Galileo
4. Saw that the moon’s surface is not smooth but covered with craters, mountains
and plains.
5. Found sunspots on the sun and saw that the sun rotated on its axis.
These and many other discoveries were instrumental in proving the Earth was not
the center of the solar system. Galileo was arrested and tried for heresy against the
church for believing this. Although he recanted his statements during the trial,
privately he s
ti
ll said what he discovered. He was sentenced to house arrest for the
last few years of his life. Those a
ft
er him eventually proved beyond a doubt that his
theories were correct and many feel he was the greatest of the early astronomers as
well as a skilled ar
ti
st and inventor. He is certainly the most well known.
Galileo’s 5th discovery the Sun has
sunspots
Galileo’s 4th discovery the moons
craters
And the Sun on it’s axis

13. Sir Isaac Newton
• Known best for his theory of Universal Gravita
ti
on, Newton’s theory
on gravity was a way of explaining the mo
ti
on of the planets and all
heavenly bodies.
•
• 2. Gravita
ti
onal forces decrease with distance.
Sir Isaac Newton
• UNIVERSAL GRAVITATION –
• 1. States every body
(planets, comets, moons,
etc) in the universe a
tt
racts
every other body with a
force that is directly
propor
ti
onal to their
masses. The larger the mass
the more the force.

14. Revolu
ti
on and Rota
ti
on
• Many people confuse these two. Be careful.
• ROTATION – The
ti
me it takes an
object to rotate on it axis. We
commonly refer to the Earth’s
rota
ti
on
ti
me on it axis, about 24
hours, as a day. Di
ff
erent heavenly
bodies rotate at di
ff
erent speeds. A
“day” on Venus for example takes
longer than its year since it
revolu
ti
on
ti
me around the sun is
actually shorter than it’s
ti
me to
rotate on its axis.
• WHICH PLANETS REVOLUTION TAKES
THE LONGEST AROUND THE SUN?
• PLUTO if you count it as a planet,
about 248 years.
• REVOLUTION – The
ti
me it
takes to revolve another
object. We commonly use
the earth’s revolu
ti
on
around the sun to discuss. It
takes the Earth about 365 ¼
days to make a complete
trip around the sun. We call
this a year. All heavenly
bodies revolve at di
ff
erent
speeds around the sun.
•
Pluto

15. ECLIPSES• Eclipses occur when a body casts a shadow
on another body. Two types occur, lunar and
solar. Eclipses can be par
ti
al or total. Several
eclipses occur each year, normally 3 or 4.
•
• LUNAR ECLIPSE - A lunar eclipse
occurs when the moon is covered
by the Earth’s shadow. The Earth is
between the sun and the moon.
•
• SOLAR ECLIPSE – A solar
eclipse occurs when the moon
casts its shadow on the Earth.
The moon is in between the
sun and the Earth.
LUNAR ECLIPSE
SOLAR ECLIPSE

16. EARTH’S MOON
• The Earth has one satellite or moon. Many people call it by the
name of LUNA. Other planets moons are commonly named. We will
study our moon and a few others in our solar system.
• Our moon is about ¼ the diameter of the Earth. In the solar system
this is considered a very large moon for a planet to have as a
satellite.
•
EARTH’S MOON
• The gravita
ti
onal force on the moon is
only 1/6th that of the Earth due to the
mass di
ff
erences between the two.
You would be able to jump higher and
carry more weight on the moon
because of the di
ff
erence. A person
who could carry 100 lbs on Earth could
carry 600 lbs on the moon. A person
weighing 150 lbs on Earth would weigh
25 lbs on the moon.
• The moon reaches a day
ti
me temperature of 127 C and a low at night of
around – 173 C.

17. EARTH’S
MOON
• Maria - Ancient beds of basal
ti
c
lava, released when asteroids or
meteorites hit the surface of the
moon millions of years ago. The
moon had volcanic ac
ti
vity then.
Craters were formed by the impact of rapidly moving debris. Since no atmosphere is present to burn
the debris up, as on earth, craters are commonplace. Some are as large as 250 km or 150 miles in
diameter. The Earth has only about a dozen large craters s
ti
ll le
ft
due to erosion on our planet. A crater
is de
fi
ned as a round depression. The more craters, the older the surface of the moon.
• The moon does not have an atmosphere. The only weathering or
erosion that takes place is caused by space dust or meteorites that
strike the surface. Craters that formed thousands of years ago are
s
ti
ll there because of this.
•

18. HOW DID THE MOON FORM?
• The current theory suggests the moon formed shortly a
ft
er the Earth. The
thought is the s
ti
ll young, hot Earth collided with another body in our solar
system breaking o
ff
part of the outer crust of the Earth, sending the other
body and the broken o
ff
part of the Earth in a revolu
ti
on around the then
scarred Earth. Over millions of years, the Earth healed and the moon
formed from the debris from the collision. The lack of a sizable iron core,
which the earth has, suggests the moon did not form from the same
materials as Earth, but from these remains. This is known as the Giant
Impact Theory. Because of this we consider the moon and the Earth to be
about the same age.

19. MOONS REVOLUTION AND ROTATION
• A “day” on the moon is thus 27 1/3 Earth days with about 2 weeks
of daylight and two weeks of darkness.
• REVOLUTION – While we are revolving around the sun, the moon
is revolving around the Earth. It takes 27 1/3 days for the moon to
make a full revolu
ti
on. As the revolu
ti
on takes place, the moon
appears to go through phases as seen from the Earth due to the
posi
ti
on of the moon in rela
ti
on to the posi
ti
on of the sun and the
Earth.
Sun’s Revolution
• INTERNET PHASE CLIP OF
THE MOON.
• The moon also takes 27 1/3
days to rotate on its axis
crea
ti
ng a “phase lock” with
the Earth. Because of this we
always see the same side of
the moon.

20. THE PLANETS
• The ancient astronomers we studied earlier only knew about 6
planets; Mercury, Venus, Earth, Mars, Jupiter and Saturn. The
other planets, Uranus, Neptune and Pluto(?) were too far away to
be seen by the naked eye and were discovered a
ft
er the inven
ti
on
of the telescope. Even Galileo with his telescope could not see
them. They were discovered much later.
Our solar system consists of our sun, the planets and their satellites or
moons, asteroids, comets, space debris, meteoroids and dust.
• The planets and their moons make up the most visible and studied
bodies besides our sun.

21. PLANET CLASSIFICATION
• PLUTO – Now thought to be a wanderer
picked up by our suns gravity. The structure
does not
fi
t its place in the solar system. We
will s
ti
ll study it as many s
ti
ll consider it a
• The Jovian planets are all large, gaseous
planets with thick atmospheres that
orbit outside the asteroid belt. They
consist of Jupiter, Saturn, Uranus and
Neptune. All have rings and are not
solid
The Terrestrial planets are the small,
rocky ones closest to the sun. They
consist of Mercury, Venus, Earth and
Mars. These planets all are inside the
asteroid belt and have thin if any
atmospheres. These are the planets
most Earth like and are solid.
• PLUTO
• JOVIAN PLANETS
• TERRESTRIAL PLANETS

22. MERCURY
Mercury is the closest planet to the sun.
It is very similar to our moon’s surface since Mercury does not have an atmosphere to
deter the onslaught of space debris such as meteorites from striking the surface.
Mercury does not have any satellites.
Mercury does not have any rings.
Mercury is a terrestrial planet.
Mercury orbits the sun in about 88 days, the fastest of all. Mercury rotates in about 160 days
or longer than its orbit.
Rotates on
ti
s axis every 59 days.
• Mercury has a day
ti
me temperature of over
427 degrees C , but drops to – 173 C at
night because without an atmosphere no
greenhouse gases are available to warm the
planet.

23. VENUS
• Second planet from the sun and the brightest object in the night sky except for
the moon.
• Has a yellow color because its volcanoes emit sulfur.
•
• Venus rotates backwards from its orbit.
• Inner or terrestrial planet.
• Venus does not have a satellite or moon.
• Has phases as seen from Earth. WHY? Homework , explain why.
• Its day is longer than its year. WHY? Homework, explain why.
• Dense carbon dioxide atmosphere leads to highest
temperature in the solar system, 475 C, except sun.
Homework, Why is Venus ho
tt
er than Mercury when
Mercury is closer to the sun?
• Called Earth’s twin because of the size similari
ti
es.
•

24. EARTH
• The third planet from the sun.
• Only planet with liquid water on the surface.
• Has one satellite
• Terrestrial planet
•
• Only planet with life as we
know it.
• Also called the Blue Planet
and the Water Planet
• 1 AU or astronomical unit
from the sun.
• Homework: What is an astronomical unit?
• Revolves around the sun every 365 days or one year.
• Rotates on its axis about every 24 hours.

25. Mars
• Known as the red planet because of the iron oxide surface, or rust.
• Shows evidence of past water on the surface such as old channels or stream
beds and gullies.
• 4th planet from the sun.
• Terrestrial
• Takes 687 days to revolve around the sun but rotates just a li
tt
le longer than
Earth.
• Has 2 moons. What are they named
and how do scien
ti
st think they
formed?
• Has huge volcanoes, one of which,
Mons Olympus, is the largest known in
the solar system. It is the size of the
state of Ohio and is 23 km or about 14
miles high.
•

26. JUPITER
• 5th planet from the sun.
• Largest of the planets. All the other planets and their
moons would
fi
t inside Jupiter.
• Jovian or a gas planet.
• Has rings but very dark and faint.
• Takes 12 years to revolve around the sun but only 9.8
hours to rotate on its axis.
Great Red Spot seen from Earth is a
centuries old storm that has been
there as long as man has seen
Jupiter.
Has at least 63 moons or satellites.

27. SATURN
• 6th planet from the sun
• Has at least 48 moons.
• Has the most visible ring system made of ice
and dust that is very re
fl
ec
ti
ve.
• Takes 29.5 years to revolve around the sun but
only about 10 hours to rotate on its axis.
• Jovian, gas planet
• The second largest planet

28. URANUS
• 7TH Planet from the sun.
• Jovian, gas planet
• Has ring system
• Rotates with the plane of its orbit, like a ball rolling
around the sun. Nicknamed the sideways planet
because of this.
• Has at least 25 satellites
• Takes 84 years to orbit the sun but only about 17
hours to rotate on its axis.

29. NEPTUNE
• 8TH Planet from the sun.
• Jovian, gas planet
• Windiest planet. Wind over 600miles per hour.
• Great dark Spot comes and goes.
• At least 13 satellites. Triton, one of the 13 is the
coldest surface temperature in the solar system
but has volcanoes.
• Has a ring system
• Takes 165 years to orbit the sun but only 16 hours
to rotate on its axis.

30. PLUTO
• 9th object or planet(?) from the sun.
• Does not follow the pa
tt
ern of the other outside or
Jovian planets. Most think our sun captured it as it
wandered through space.
• Rotates on its axis about every 6.4 days.
• Has at least one known moon, Charon, and now
reports of two more are being issued.
• Smallest of the planets.
• Kind of a dirty iceball in
space.
• Eccentric orbit brings it
inside Neptune's’ orbit for
about 22 years of its 248
year orbit around the sun.

31. Asteroid Belt
• Most asteroids lie between the orbits of
Mars and Jupiter.
• Most are small rocky bodies that are
irregularly shaped about 1 km across.
Some are large as is CERES, the largest at
over 1000 km in diameter. Some are
small, the size of sand.
• Most orbit the sun every 3 to 6 years.

32. JOVIAN OR TERRESTRIAL?
• The 4 inner planets are terrestrial or rocky and Earth-like with thin if
any atmospheres.
• Terrestrials are small when compared to the Jovian Gas Giants.
• Terrestrials do not have rings.
• Terrestrials are dense when compared to the Jovian planets. Saturn
would actually
fl
oat on water.
• All Jovian planets, or outside planets; Jupiter, Saturn, Uranus and
Neptune are huge gas giants with thick atmospheres.
• All Jovian's have rings.
• Pluto does not
fi
t in either category.
• WHAT DO WE MEAN BY INSIDE OR OUTSIDE PLANET?
JOVIAN PLANETS TERRESTRIAL PLANETS