The Universe

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1. The history of knowledge of the universe.
2. The celestial bodies in the universe.
3. Dimensions and distances in Astronomy.
4. The stars and the galaxies.
4.1. The stars.
4.2. The galaxies.
4.2.1. Our galaxy: The Milky Way.
5. The Solar System.
Pepi Jaramillo Romero
Dpto. Física y Química

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SECOND CENTURY
Ptolomy suggested a GEOCENTRIC ASTRONOMIC MODEL
The Sun, the moon and the five known planets ( Mercury, Venus,
Mars, Jupiter and Saturn ) all revolved around the Earth
They were well-known in ancient times because they can be easily seen with
the naked eye and their movements are easily differentiated from stars which are in a
fixed position.

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1543 Published his HELIOCENTRIC MODEL
Copernicus
However, hundreds years before the
Greek astronomer Aristarchus of Samos
sugestted that the Earth revolved
around the Sun
The planets revolved
around the Sun

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17th CENTURY
In 1609 Galileo used a
telescope for the first
time to observe the
night sky. This was the
birth of modern
astronomy.
At the end of the same century, Isaac
Newton built the first telescope using
mirrors instead of lenses. Newton
published his book The Principles of
natural Philosophy in which he
explained the laws governing the
movement of the planets.

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CTIVITY ONE
Find some information
about the origin of the universe,
especially about The Big Bang
Theory.
Please, write a summary using
your own words.
REMEMBER: DO NOT COPY AND
PASTE.

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4.1. The stars.
4.2. The galaxies.
4.2.1. Our galaxy: The MilkyWay.

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The celestial
bodies in the
universe are very
diverse. The
properties of a
planet, for
example, are very
different to those
of a star, so the
temperature is
very high on a star
(millions of
degrees Celcius).

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TYPES OF CELESTIALS
BODIES
PLANETS
COMETS
SATELLITES
ASTEROIDS
CLUSTER OF GALAXIES
STARS
GALAXIES
DWARF PLANETS

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Like the Earth, which is the planet we live on.
PLANETS
The planets
shine by
reflecting
light from
the Sun.

DWARF PLANETS
What is a planet?
We've been asking that question at least since Greek
astronomers came up with the word to describe the bright points
of light that seemed to wander among fixed stars.
Many disagreed in 1930 when Pluto was added as our solar
system's ninth planet. The debate flared again in 2005 when Eris --
about the same size as Pluto -- was found deep in a zone beyond
Neptune called the Kuiper Belt. Was it the 10th planet? Or are Eris
and Pluto examples of an intriguing, new kind of world?

DWARF PLANETS
The International Astronomical Union decided in 2006 that a
new system of classification was needed to describe these new
worlds, which are more developed than asteroids, but different
than the known planets. Pluto, Eris and the asteroid Ceres became
the first dwarf planets. They are orbiting the sun in zones of similar
objects such as the asteroids.
Our solar system's planet count now stands at eight. But the
lively debate continues as we continue to explore and make new
discoveries.

DWARF PLANETS

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Like the moon, which is the Earth’s only natural
satellite.
SATELLITES

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Which orbit around the Sun on a very long
trajectory.
COMETS

The comet Halley will COMETS
return in 1758

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ASTEROIDS
Rocky bodies which are smaller than planets,
very often irregular in shape, and which orbit
around the Sun.

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Like the Sun which continuously radiates energy
into the space around them
STARS

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GALAXIES
Groups of tens or
hundreds of
thousands of stars. It
is thought that the
universe contains
approximately 100 000
galaxies.

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CLUSTER OF GALAXIES
Made up of many
different galaxies.

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The size of the celestial bodies is quite incredible as is the distance
between these ones too.
EXAMPLE
A space ship travelling at 40 000 km/h (usual speed)
would take 100 000 years to reach the nearest star
to the Sun.
This is why we use the term LIGHT YEARS when we want to talk
about astronomics distances.
LIGHT YEARS Distance covered by light in a year.
C = 300 000 km/s

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Astronomer also use another unit
ASTRONOMICAL UNIT (A.U.)
Distance between the Sun and the Earth
1 A.U. = 150 000 000 km

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4.1. The stars.
If we look at the night sky on a clear night and well away
from the city light we can see hundreds of small lights which
seem to be twinkling.
STARS
Stars have differents characteristics
LIGHT
SIZE
COLOUR
BRIGHTNESS

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4.1. The stars.
COLOUR
Not all stars are white as they at first appear. More
careful inspection reveals that stars come in a wide
range of colours. Some are bluish, reddish, orange. The
Sun is a yellow star. The colour of a star depends on its
surface temperature, with the coolest stars being the
reddest and the hottest ones the bluest

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4.1. The stars.
SIZE
The stars come in a wide range of sizes. The largest
stars, known as giants and supergiants, are hundreds
of times the diameter of the Sun. In fact, the Sun is a
medium sized star. For example, Betelgeuse, a star in
the constellation of Orion is 600 times bigger than the
Sun. On the other hand, Sirius B in the constellation of
Canis Major is 100 times smaller than the Sun.

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4.1. The stars.
BRIGHTNESS
Star brightnesses are expressed in terms of
magnitudes. This system was started by the Greek
astronomer Hipparchus in the second century B.C. He
divided the stars into six categories of brightness, from
the brightest stars (first magnitude), to the faintest
stars that he could see (sixth magnitude). Nowadays
stars brightnesses are measured to the nearest
hundredth of a magnitude by sensitive instruments
known as photometers.

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4.1. The stars.
Some stars emits more light than others. Two stars
emitting the same amount of light will not be as bright
as each other if they are at different distances from
the Earth.
LIGHT

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4.1. The stars.
The sky is divided up into 88 areas, known as constellations,
which serve as a convenient way of locating the position of
objects in the sky.
CONSTELLATIONS
Constellations come in many different shapes and sizes. The
tradition of dividing the sky into constellations began
thousands of years ago when ancient people assigned certain
star patterns the names of their gods, heroes and fabled
animals.

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4.1. The stars.
The brightest and biggest
stars are shown on a
PLANISPHERE

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4.1. The stars.
A
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CTIVITY TWO
Try to find the constellatios of
Orion, Leo, Cassiopeia, Ursa Major,
Ursa Minor, Polaris star and Lepus.
Can you find all the stars on
the planisphere by looking at the
night sky in your region?
Why do we need very dark
nights to be able to observe the star?

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4.2. The galaxies.
Galaxies extend into space as far as the largest telescopes
can see. Each is a collection of millions or billions of stars held
together by the mutual attraction of gravity.
Galaxies are classified according to their shapes. There
are two main forms:
ELLIPTIC
SPIRAL
IRREGULAR
More or less spherical
A flat disc with several arms coming
out of the nucleus of the spiral
They have not specific shape

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4.2. The galaxies.
4.2.1. Our galaxy: The MilkyWay.
All the stars visible to the naked eye are part of an
enormous system of at least 100 000 million stars known as The
Milky Way. Our Galaxy has a spiral shape. The entire Galaxy is
rotating; our Sun takes about 250 million years to complete one
orbit around the centre of the Galaxy.
The nearest galaxy to our own is Andromeda which is
more than two million light years away. This means that when
we look at this galaxy we are seeing it as it was more than two
million years ago.

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CTIVITY THREE
What type of galaxy is The
Milky Way ?
Are there more stars in the
swirls spiralling out from the centre
or near the nucleus ?

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Our planetary system is formed 5000 million of years ago
from nebulas’ gases and dust. The Sun is in his centre and it is
made up of two gases: Hydrogen and Helium. The planets,
satellites, comets and asteroids revolve around the Sun.
The comets and the asteroids are smaller bodies. Comets
show their spectacular tails when they come close to the Sun.
Many are concentrated in a region located between the orbits of
Mars and Jupiter known as the ASTEROID BELT.

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The planets revolve around the Sun in eliptical orbits. The
planets which are farthest away revolve more slowly and take
longer to complete a full revolution.
The planets can be classified
TERRESTRIAL
PLANETS
(They have a solid
surface)
GAS GIANT PLANETS
(They do not have a
solid surface)

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TERRESTRIAL PLANETS
The closest planet to the
Sun, only slightly larger than Earth’s
moon. Like the Moon, Mercury has
very little atmosphere to stop
impacts, and it is covered with
craters. Mercury's dayside is super-heated
by the Sun, but at night
temperatures drop hundreds of
degrees below freezing. Ice may even
exist in craters. Mercury's egg-shaped
orbit takes it around the sun
every 88 days.
MERCURY

TERRESTRIAL PLANETS VENUS
The brightest planet, Venus,
outshines every star in the sky. It is
frequently seen rising before the Sun
in the morning sky, when it is
popularly known as the morning star,
or setting in the evening twilight when
it is termed the evening star. Venus is
a dim world of intense heat and
volcanic activity. Similar in structure
and size to Earth, Venus' thick, toxic
atmosphere traps heat in a runaway
"greenhouse effect."

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TERRESTRIAL PLANETS
Earth is an ocean
planet. Our home world's
abundance of water -- and life --
makes it unique in our solar
system. Other planets, plus a
few moons, have ice,
atmospheres, seasons and even
weather, but only on Earth does
the whole complicated mix
come together in a way that
encourages life -- and lots of it.
EARTH

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TERRESTRIAL PLANETS
MARS
Mars is a cold desert world.
It is half the diameter of Earth and
has the same amount of dry land.
Like Earth, Mars has seasons, polar
ice caps, volcanoes, canyons and
weather, but its atmosphere is too
thin for liquid water to exist for long
on the surface. There are signs of
ancient floods on Mars, but
evidence for water now exists
mainly in icy soil and thin clouds.

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GAS GIANT PLANETS
Jupiter, the most massive
planet in our solar system -- with
dozens of moons and an
enormous magnetic field -- forms
a kind of miniature solar system.
Jupiter does resemble a star in
composition, but it did not grow
big enough to ignite. The planet's
swirling cloud stripes are
punctuated by massive storms
such as the Great Red Spot, which
has raged for hundreds of years.
JUPITER

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GAS GIANT PLANETS
Adorned with
thousands of beautiful
ringlets, Saturn is unique
among the planets. All four
gas giant planets have rings -
made of chunks of ice and
rock - but none are as
spectacular or as
complicated as Saturn's. Like
the other gas giants, Saturn
is mostly a massive ball of
hydrogen and helium.
SATURN

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GAS GIANT PLANETS
URANUS
Uranus is the only
giant planet whose equator is
nearly at right angles to its
orbit. A collision with an Earth-sized
object may explain
Uranus' unique tilt. Nearly a
twin in size to Neptune, Uranus
has more methane in its mainly
hydrogen and helium
atmosphere than Jupiter or
Saturn. Methane gives Uranus
its blue tint.

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GAS GIANT PLANETS
NEPTUNE
Dark, cold and
whipped by supersonic winds,
Neptune is the last of the
hydrogen and helium gas
giants in our solar system.
More than 30 times as far from
the sun as Earth, the planet
takes almost 165 Earth years to
orbit our sun. In 2011 Neptune
completed its first orbit since
its discovery in 1846.

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CTIVITY FOUR
What do you think caused the
craters on the surface of Mercury ?
Why do the photograghs of
Pluto show very little detail?
Could we send a spaceship to
land on Jupiter or Saturn? Explain
your answer.

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A
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CTIVITY FIVE
Which planets take the longest
in orbiting the Sun ?
Which planets have the longest
days and which planets have the
shortest days?
Which planets are a similar size
to the Earth?

The Universe

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