4. 1. WHAT IS THE UNIVERSE LIKE?
Geocentric theory
Suggested by Aristotle
(4th century B.C.)
Formalised by Ptolomy.
(2nd century A.D.)
The Earth was the
center of the Universe.
The Sun, Moon and
planets orbited the
Earth.
5. 1. WHAT IS THE UNIVERSE LIKE?
Heliocentric theory
Proposed by Nicolaus
Copernicus in 1542
Verified by Galileo
(Invented the
telescope)
The Sun was the
center of the
Universe
6. 1. WHAT IS THE UNIVERSE LIKE?
Johannes Kepler discovered the elliptical
movement (17th
century)
8. WHAT UNIT OF MEASUREMENT DO
ASTRONOMERS USE?
Astronomical unit (AU) is the distance between
the Earth and the Sun= 150 million kilometres.
Express the distance of Mercury, Mars and Pluto
from the Sun in kilometres:
Mercury: 0,4 AU =
Mars: 1,5 AU=
Pluto: 39,4 AU=
Light year. It is the distance light travels in a
year. Light travels 300,000 km per second.
0,4 x 150.000.000 = 60.000.000 Km
1,5 x 150.000.000 = 225.000.000 Km
39,4 x 150.000.000 = 5.910.000.000 Km
This distance is equivalent to roughly
9,461,000,000,000
9.
10. GALAXIES
•Galaxies are
a vast
collection of
stars, dust
and gases.
•They appear
in groups
called galaxy
clusters.
(Local Group
is our galaxy
cluster)
•Our galaxy is
the Milky
Way.
17. SUN
It’s a medium-sized star.
The Sun consists mainly
of two gases: 75%
hydrogen (H) and 25%
helium (He).
Temperature of the
nucleus 15.000.000 ºC.
So hot inside that it
emits heat and light
through nuclear fusion.
Surface temperature of
5,500 ºC
It rotates on its axis in
an anticlockwise
direction (once every 25-
30 days)
It was formed when clouds of gases pull together by gravitational forces
4,600 m.y. ago.
18. What is the name of the process that takes
place inside the Sun’s nucleus?
What happens during this process?
20. PLANETS
Planets are
spherical bodies
which revolve
around the Sun.
They move in
elliptical orbits.
Mercury, Venus,
Earth and Mars
are made up
mainly of rock.
(Rocky planets)
Jupiter, Saturn,
Uranus and
Neptune are made
up mainly of
gases. (Gaseous
planets)
Rocky planets or
inner planets
have a crust and
a mantle made
of rock and a
metallic core.
Gaseous planets
or outer planets
are made up
mainly of gas.
23. Mercury
Mercury is the closest planet to the Sun
It is the smallest planet in the Solar
System
It has no natural satellites.
It has no atmosphere
There are lots of craters on its surface
Huge differences in night and day
temperatures (From -170ºC to 425ºC)
24. Venus
Venus is similar in size to Earth.
It has an extremely dense atmosphere
which consists mainly of carbon dioxide
(CO2). This thick atmosphere makes it the
hottest planet of the planetary system, with
surface temperatures over 450°C.
Venus has no natural satellites.
One day in Venus lasts more than one Earth
year.
25. Earth
Earth is the largest and densest of the
inner planets
It’s the only planet known to have life.
Its liquid hydrosphere is unique among
the inner planets. (Average surface
temperature = 15ºC)
Earth's atmosphere has been altered by
the presence of life to contain 21% free
oxygen. (78% N2)
It has one satellite, the Moon.
26. Mars
Mars is smaller than Earth and Venus.
It has a thin atmosphere that contains
95% carbon dioxide, so it’s not
breathable.
It’s surface resemble the Earth’s rocky
deserts.
Mars has two tiny natural satellites
(Deimos and Phobos).
28. Jupiter
Jupiter is the largest planet of the Solar System.
It is composed largely of hydrogen (90%) and
helium (10%).
Jupiter has more than 60 known satellites.
The four largest satellites are Ganymede,
Callisto, Io, and Europa.
There are bands of different coloured clouds
around the planet, parallel to the equator.
Cloud storms
29. Saturn
Saturn, famous for its extensive ring
system made of ice, small rocks and dust
particles.
Its composition is very similar to
Jupiter’s. (97% Hydrogen, 3% Helium)
Saturn also has more than 60 known
satellites. The largest one is Titan.
30. Uranus
Uranus is the lightest of the outer
planets.
It’s a frozen planet, with very low
surface temperatures.
One unique feature of Uranus is its axial
tilt. The planet rotates on its side with a
tilt over ninety degrees to the
ecliptic.
It also has a ring system
Uranus has 27 known satellites.
31. Neptune
Neptune is slightly smaller than Uranus.
It has 13 known satellites. The largest
one is Triton.
37. Asteroids
Between the orbits of Mars and Jupiter is
located the Main Asteroid Belt.
Asteroids are rocky bodies with irregular
shape.
38. Comets
Comets are composed largely of volatile ices,
dust and fragments of rock. When a comet
enters the inner Solar System, its proximity to
the Sun causes its icy surface to sublimate and
ionise, creating a coma, which is a long tail of
gas and dust often visible to the naked eye.
Short-period comets, such as Halley's
Comet, are believed to originate in the
Kuiper belt (30-1.000 A.U. from the Sun),
while long-period comets, such as Hale-
Bopp, are believed to originate in the Oort
cloud (60.000 A.U. from the Sun)
Coma
42. Questions on unit 1
1. What is a galaxy?
2. What’s the name of our galaxy?
3. Why does the Sun look much brighter than
other stars?
4. What’s the name of the big explosion at the
beginning of the Universe?
5. When did it happen?
6. Does a light year measure distance or time?
7. Imagine that Betelgeuse, a star located 600
light years away from the Earth, explodes next
month. When will it be possible to see the
explosion from our planet?
43. 8. What are the components of the Solar System?
9. Write down the names of the inner planets,
starting with the one closest to the Sun.
10. Name the planets that are made of gas.
11. Which of the planets is more similar to the
Earth in:
…its distance from the Sun?
…the number of moons it has?
…its size?
44. HOW DO THE PLANETS MOVE?
http://esminfo.prenhall.com/science/geoanimation
s/animations/01_EarthSun_E2.html
