The universe contains galaxies, stars, and planetary systems. One theory is the Big Bang, in which the universe began as a giant explosion. Afterward, matter started to group together to form celestial bodies like stars and planets. The solar system is located at the edge of the Milky Way galaxy and contains the Sun and objects that orbit it, including planets, asteroids, comets, and moons. The Earth revolves around the Sun while rotating on its axis, causing the cycle of day and night and the seasons.

1. THE UNIVERSE

2. THE UNIVERSE
O Include planets,
stars, solar systems
and galaxies.
O One theory is the Big
Bang:
O Giant explosion.
O After the Big Bang,
the matter in the
Universe started to
group together to
form the different
Celestial Bodies.

3. O STARS
O Huge balls of gas where nuclear reactions take
place.
O Produce light and heat.
O Classified according to: colour, luminosity and
size.
O CONSTELLATION
O Group of stars which make an imaginary shape in
the night sky.
O They are named according to their shape.
O Great Bear.

4. O GALAXY
O Enormous system of
stars, dust and gas.
O Different shapes: spiral,
elliptical or irregular.
O GALAXY CLUSTERS
O Hundreds or even
thousands of galaxies.
O PLANETS and DWARF
PLANETS
O They orbit a star and do
not emit light.
O Some planets have
satellites in their orbit
(which do not emit light
either.)
O Pluto is a dwarf planet.

5. O COMET
O Is made of ice, dust and gases
O ASTEROID
O Is a rocky, irregular mass that orbits the Sun.
O Can have different sizes.
O Most asteroids take three or six years to orbit the Sun.
O METEOROIDS
O Small pieces of rock or metal from an asteroid or comet.
O METEOR is called when it passes through the Earth´s
atmosphere and it burns.
O METEORITE, when a meteor hits the Earth´s surfaces.

6. THE SOLAR SYSTEM
O Located at the edge of the Milky Way.
O It is made up of the Sun and the celestial
bodies: planets, natural satellites,
asteroids, comets and meteoroids

7. THE SUN
O It is a star at the centre of the Solar System
and at the edge of the Milky Way.
O It is a huge ball made up of gases
(hydrogen and helium)
O It is 110 times larger than the Earth.
O Rotates on its axis.
O It also orbits around the centre of the Milky
Way.
O It takes the Sun about 220 million year to
complete one orbit.

8. O PLANETS
O Orbit the Sun.
O Classified into two groups
O Inner planets (Mercury, Venus, Earth, Mars):
O solid and have a rocky surface.
O They are smaller and warmer than the outer planets.
O Outer planets (Jupiter, Saturn, Uranus and
Neptune):
O Called gas giants because (made up of gases).
O Cold, dark and they have rings and many moons.
O ASTEROIDS
O They are found in two regions:
O Asteroid belt: between Mars and Jupiter.
O Kuiper Belt, beyond Neptune.
O NATURAL SATELLITES or MOONS
O Orbit some of the planets.
O Earth has only one natural satellite.

9. MODELS
O GEOCENTRIC
O Ancient Greeks.
O The Earth was at
the centre of the
Universe.
O Sun, Moon,
planets and stars
orbit the Earth.
O HELIOCENTRIC
O Nicolaus
Copernicus.
O The Sun was at
the centre of the
Universe.
O The Earth and
other planets orbit
the Sun.

10. THE EARTH
O It is the only planet
where life has been
found.
O 75% of the surface
of the planet is
water, so the Earth
looks blue from the
space.
O The Earth moves in
two different ways
O Rotation
O Revolution

11. O The Earth rotates anticlockwise on its axis.
O The axis is an imaginary line that goes from
the North Pole to the South Pole and it is
tilted at about 23 degrees.
O It takes 24 hours for the Earth to complete
one rotation. And this rotation give us day
and night
O At the Equator, day and night are the same
length all year.
O In the poles, winter nights become longer and
summer days become longer.

13. O It takes the Earth just 365 days to orbit the Sun:
In this period, we experience the season.
O Our part of the planet receives more or less light
during different months because the Earth´s
axis is tilted.
O When the Northern hemisphere is tilted
towards the Sun, it is summer.
O When the Northern hemisphere is tilted away
from the Sun, it is winter.
O Solstice or equinox is the first day of a season.
They are the opposite in the Norther than the
Southern Hemisphere.

15. THE MOON
O It is the Earth´s only natural satellite.
O It is around four times smaller than the
Earth.
O There is no air or atmosphere on the
Moon.
O It rotates on its axis and orbits around the
Earth (28 days to complete one revolution
and one rotation)
O The Moon´s surface is rocky and has
craters and mountains.
O We can see the Moon because it reflects
sunlight. Phases of the Moon.

17. TIDES
O The Moon has a great
influence on our
planet. Its gravity
pulls at the water in
the oceans and
creates tides.
O Tides are periodic
changes in sea level.
Every day, we
experience two high
tides and two low
tides.

18. ECLIPSES
It occurs when a celestial body moves
into the shadow of another.

20. The Earth blocks the sunlight
and casts a shadow on the
Moon