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ESO1
THE UNIVERSE AND THE EARTH
Unit 8
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What is the Universe like?
Ideas about the
Universe:
Geocentric theory
Aristotle (B.C)
and Ptolomy
(A.D)
Heliocentric
theory
Copernicus in
1542 Galileo
Galilei invented
the telescope
Johannes
Keppler
1571verified this
theory
Unit 1
Unit 8
Universe theories
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The current concept of the
universe
Current Ideas
about the
Universe:
It is made up of
matter and energy
Galaxies (stars
and nebulas)
Stars and stellar
wind
Big Bang
(expanding
theory)
Unit 1
Unit 8
Universe theories
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The expanding universe Unit 1
Unit 8
Universe theories
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How big is the
Universe?
Astronomical unit (AU): this is equal to the distance between the
Earth and the Sun. Distances between planets in our Solar
System are expressed in astronomical units
1UA: 150 million kilometres
Compare the distance of these planets from the Sun:
Planet Distance from Sun (AU)
Mercury 0.39
Venus 0.72
Earth 1.00
Mars 1.52
Jupiter 5.20
Saturn 9.54
Uranus 19.19
Neptune 30.06
Unit 8
Universe units
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How big is the
Universe?
Unit 8
Astronomical unit (AU) Universe units
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How big is the
Universe? Unit 1
Light-year (ly): this is the distance that light travels in a year at its
normal speed (300 000 km per second).
Galactic dimensions and the distances to other galaxies or to other
objects in the universe that are far away are expressed in light-
year.
One ly is equal to just under 10 trillion kilometers.
Source of light Time to reach the earth
The Sun 8 mins. 20 sec
Centauri, the nearest star 4 light-years
Betelgeuse 500 light-years
The Andromeda Galaxy 2.3 million light-years away Unit 8
Universe units
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What makes up the
Universe?
Unit 8
Components of the
Universe
• Galaxies are grouped
together in galaxy clusters.
• Galaxies contain nebulae
(clouds of dust) and star
cluster (a lot of stars
together)
• Stars are massive spherical
bodies of gases. Some stars
have planetary systems
with planets, satellites,
asteroids and comets (e.g
the Sun)
Universe made up
of
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What makes up the
Universe?
Unit 8
Nebulae are
very large
clouds of
dust and
gases
(hydrogen and helium)
The Trifid Nebula
Nebula
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What makes up the
Universe?
Unit 8
The Eagle Nebula The Rosette Nebula
Nebula
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What makes up the
Universe?
Unit 8
Star cluster
are
composed of
lots of stars
that are very
close to each other
Globular star cluster
Star cluster
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What makes up the
Universe?
Unit 8
The Milky Way is
the galaxy that
contains our Solar
System
Its name derived
from its
appearance ( a
thick white band
across the dark
sky) Globular star cluster
Our Galaxy: The Milky Way Galaxies
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What makes up the
Universe?
Unit 8
The Milky Way is a spiral galaxy
Galaxies
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What makes up the
Universe?
Unit 8
Components:
Nucleus (bulge)
with old stars
Disk (spiral arms)
with the youngest
stars, the Sun is
in Orion Arm
Halo with isolated
stars Globular star cluster
• Our Galaxy: The Milky Way Galaxies
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What makes up the
Universe?
Unit 8
• Stars are large spheres of hydrogen and helium that release energy
• Nuclear fusion (hydrogen particles combine to form helium and release energy)
Stars
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What makes up the
Universe?
Unit 8
Properties:
• Brightness depends on
the distance between
the star and us
• Colour depends on the
surface temperature
Stars
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What makes up the
Universe?
Unit 8
Stars Class Temperature (ºK) Color Example
O 30 000-60 000 Blue Alnitak, Mintaka
B 10 000- 30 000 Blue-White Rigel, Spica
A 7 500- 10 000 White Vega, Sirius
F 6 000- 7 500 White Procyon, Canopus
G 5 000- 6 000 Yellow- White Capela, The Sun
K 3 500- 5 000 Orange Epsilon, Eridanus
M 2 000- 3 000 Red Barnard’s Star, Glese
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What makes up the
Universe?
Unit 8
Stars
• The Sun a medium-sized G- type star
• 75% hydrogen, 25% helium, oxygen, carbon,…
• Rotation is anticlockwise
• It takes between 25 (at equator) and 30 days (at poles)
• Tº 5778 K (5505 °C) • Diameter 1 400 000
km
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What makes up the
Universe?
Stars
Unit 8
• Rotation of the Sun
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What makes up the
Solar System?
Unit 8
Components of the
Solar System
• The Sun a medium sized- G-
type star
• The Planets (spherical
bodies which orbit the Sun:
inner planets: Mercury,
Venus, Earth, Mars, outer or
gas planets :Jupiter, Saturn,
Uranus and Neptune)
• The Dwarf planets (small
spherical bodies which orbit
the Sun Pluto,Ceres, Eris
• The Satellites (natural objects
that move around the
planets), e.g the Moon
• The Comets (rocks , dust and
ice), e.g Halley’s Comet
The Solar
System
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What makes up the
Solar System?
Unit 8
Components of the
Solar System The Solar
System
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The asteroid belt is the region of the Solar System located between the orbits of Mars and Jupiter.
What makes up the
Solar System?
The Solar
System
Unit 8
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What makes up the
Solar System?
Unit 8
The Solar
System
• Asteroids are rocky objects which irregular shape
• Asteroids orbit the Sun, most of them are between Mars and Jupiter
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What makes up the
Solar System?
Unit 8
The Solar
System The Kuiper belt is a region beyond Neptune that is full of comets
(e.g Halley’s comet), asteroids and other debris. It circles the
solar system and has always been a little bit of a mystery as it is
so far away and hard to explore
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What makes up the
Solar System?
Unit 8
The Solar
System
Comets: are small bodies
that travel around the Sun
in highly elliptical orbits.
They are irregular in shape.
The nucleus is made up of
a mass of ice, dust and
gas. When comets travel
close to the Sun, some of
the ice evaporates, creating
the long, bright tails of the
comets.
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What makes up the
Solar System?
Unit 8
The Solar
System
• Oort Cloud is a
spherical cloud
of predominantly
icy planetesimals
• ic that may lie roughly
that lie 50,000
AU or 1 light-
year from the
Sun.
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What makes up the
Universe?
Unit 8
Planets
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What makes up the
Universe?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Planets
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What makes up the
Solar System?
Unit 1
Dwarf Planets
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What makes up the
Solar System?
Unit 1
Dwarf Planets
Ceres: It is a rock–ice body 950 km (590 mi)
in diameter and the smallest identified dwarf
planet.
Eris is may be larger than Pluto.
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Movements of the Earth
Seasons
Unit 1
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Movements of the Earth
Seasons
The Earth has two movements: revolution and rotation
Revolution (the earth orbits around the Sun), revolution causes the seasons, equinoxes and solstices
Rotation (the earth spins around its own axis)
The rotation of the Earth every 24 hours causes day and night
The tilt of the axis determine the lenght of the day and night during the different seasons
Rotation (North Pole) is anticlockwise (from west to east) so the Sun rises in the east
Unit 1
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Movements of the Earth
Seasons The axis of the Earth is an imaginary line on
which the Earth rotates.
It links up the two poles.
Both, the axis and the Earth are titled at an angle of 23º5’ during a revolution.
When the Sun is directly overhead we call this the overhead Sun at this time the Earth surface and the midday sun forms a 90 degrees angle.
Unit 1
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Movements of the Earth
Seasons
Spring equinox: on the 21st or 22nd mars the overhead sun is over the Equator.
The Equator receives the largest amount of solar radiation.
At this time the northern hemisphere is in the spring equinox while the southern hemisphere is in the autumn equinox. The angle of the Sun decreases towards the Poles.
On this day the two hemispheres receives a similar amount of solar radiation and the length of days and nights is the same in all the places on the Earth. After this day it is spring in the northern hemisphere where the day is longer than the night.
Unit 1
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Movements of the Earth
Seasons
Summer solstice 21st or 22nd the June the overhead Sun
is over the Tropic Cancer. It receives the largest amount of solar radiation.
At this time the northern hemisphere is in the summer solstice while the southern hemisphere is in the winter solstice. The angle of the Sun decreases towards the Poles.
On this day the length of daytime of the northern hemisphere is the longest in the year while that of the southern hemisphere is the shortest in the year.
Besides there are twenty four hours of daylight at the Artic Circle and twenty four hours of darkness at the Antarctic Circle.
Unit 1
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Movements of the Earth
Seasons
Autumn equinox 22nd or 23rd September, the overhead Sun is over the Equator again. The Equator receives the largest amount of solar radiation.
On these days the northern hemisphere is in the autumn equinox while the southern hemisphere is in the spring equinox. The angle of the Sun decreases towards the Poles.
On these days the two hemispheres receives a similar amount of solar radiation, and the length of day and night is the same as all places on the Earth.
After this day it is autumn in the northern hemisphere where the day is shorter than the night. In the southern hemisphere it becomes spring where the day is longer than the night.
Unit 1
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Movements of the Earth
Seasons
Winter solstice 21st or 22nd the December, the overhead Sun is over the Tropic of Capricorn. It receives the largest amount of solar radiation.
On these days the northern hemisphere is in the winter solstice while the southern hemisphere is in the summer solstice. The angle of the Sun decreases towards the poles.
On this day the length of daytime in the northern hemisphere is the shortest in the year, while that on the southern hemisphere is the longest in the year. There are 24 hours of darkness at the Artic Circle and 24 hours of daylight at the Antarctic Circle.
Unit 1
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Movements of the Earth
Seasons
The Earth have two movements: revolution and rotation
Revolution (the earth orbits around the Sun), revolution causes the seasons, equinoxes and solstices
Rotation (the earth spins around its own axis)
The rotation of the Earth every 24 hours causes day and night
The tilt of the axis determine the lenght of the day and night during the different seasons
Rotation (North Pole) is anticlockwise (from west to east) so the Sun rises in the east
Unit 1
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The Earth’s natural
satellite
The Moon
The Moon moves in two different ways at he same time:
Revolution: around the Earth (lunar orbit), it takes 28 days
Rotation: around its own axis, which also takes 28 days
Unit 1
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The Moon
The Earth’s natural
satellite
• Why the same side of the Moon always faces the Earth?
Unit 1
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Phases of the Moon
Each month our Moon passes through eight phases. These phases are named after how much of the moon we can see, and whether the amount visible is increasing, or decreasing each day.
Unit 1
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Tides
Tides occur due to the attraction between the Earth and the Moon, and between the Earth and the Sun.
Unit 8
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Tides
Unit 8
Spring tides • The Sun, the Earth and the
Moon are in a straight line • New Moon days and full
Moon days (two times a month)
• The water rise very high
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Tides
About every two weeks, the positions of the sun, moon, and Earth forma straight line (Figure A). At these times of new and full moon phases as viewed from Earth, the lunar- and solar-related ocean bulges also line up (and add up) to produce tides having the greatest monthly tidal range (that is, the highest high tide and lowest low tide); these are called spring tides.
Unit 8
Spring tides • The Sun, the Earth and the
Moon are in a straight line • New Moon days (the
water rise very high) • Full Moon days (the water
fall very low) • Two times a month
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Tides
Unit 8
Neap tides • Quarter Moon days • The Sun, The Moon, and the Earth
are in right angle • Neither rise very high nor fall very
low
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Tides
Between spring tides, at the first and third quarter phases of the moon, the sun's pull on Earth is at right angles to the pull of the moon (Figure B). At this time, tides have their minimum monthly tidal range (that is, unusually low high tide and unusually high low tide); these are called neap tides or fortnightly tides. Furthermore, the moon orbits Earth in an ellipse (rather than a circle) so that the moon is closest to Earth (stronger tide-generating force) at perigee and farthest from Earth (weaker tide-generating force) at apogee. The moon completes one perigee-apogee-perigee cycle once every 25.5 days.
Unit 8
Neap tides • Quarter Moon days • The Sun, The Moon, and
the Earth are in right angle
• Neither rise very high nor fall very low
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Eclipses
Solar eclipse: the Moon passes between the Sun and the Earth, and blocks off the sunlight.
Unit 8
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Eclipses
Lunar eclipse: the Moon passes behind the Earth prevents sunlight from reaching the Moon
Unit 8
The bright dancing lights of the aurora are
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The Northern Lights
Unit 8
The bright dancing lights of
the aurora are actually
collisions between
electrically charged
particles from the sun that
enter the earth's
atmosphere. The lights are
seen above the magnetic
poles of the northern and
southern hemispheres.
They are known as 'Aurora
borealis' in the north and
'Aurora australis' in the
south..
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THE END
Unit 1