Transcript AUST – HORIZON AND BEYOND part 1

AUSTRALIA – TO THE HORIZON
AND BEYOND Part 1
Yr 7 Science
Topic 4
(Chapter 5)
Space & the Universe DP 1
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Space is everything in the universe that lies
outside the Earth’s atmosphere
Much of space is vast empty and void, hence
the name – ‘Space’
No one knows how large the universe is,
special telescopes are able to see clusters of
stars (galaxies), up to 13 billion light years
away.
Our solar system
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Our solar system consists of the sun, nine
planets (and their moons), an asteroid belt, and
many comets and meteors. The sun is the
centre of our solar system; the planets, their
moons, the asteroids, comets, and other rocks
and gas all orbit the sun.
What is in space besides planets and
stars?
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Most of the universe is empty space, called a vacuum, but it is an
imperfect vacuum. There are clouds of interstellar dust and the
tiny particles that make up the solar wind. There are many isolated
particles and hydrogen atoms, which sometimes form clouds over
a billion kilometres wide called "nebulae." Besides nebulae and
interstellar dust, there are also bits of rubble as big as small
moons to as small as grains of sand. These bits of rubble are
called planetoids and asteroids. Radio, heat, and x-rays all echo
through space, as do beams of light. There is radiation bursting
forth in solar flares.
Space & the Universe cont: (DP 2)
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Light travels faster than anything in the
universe – nearly 300, 000 kms/sec.
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A light year (I.e. how far light travels in a year)
is equal to 9.5 trillion kms.
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It takes light about 8 min to reach us from the
Sun. How far away then is the Sun?
Space & the Universe cont: (DP 2)
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An Astronomical Unit (AU) is another way
(other than light years) of comparing the vast
distances of space.
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1 AU is equal to the distance of the Earth from
the Sun I.e. approx 150 million kms.
Space & the Universe cont:
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Since light takes so long to reach earth we see
objects as they ‘were’, not as they ‘are’.
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For example we see some bright stars as they
were 1800 years ago, in the time of ancient
Rome!
Major Features of the Universe (DP 1)
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Stars (like our Sun) are huge fiery balls of incredibly
hot gas. Primarily stars are made up of two gases – 3
quarters hydrogen and 1 quarter helium. They create
energy through nuclear reactions (millions of times
more powerful than a nuclear bomb). Reactions are
caused by squeezing atoms of hydrogen gas deep
inside the star.
A star will continue to glow, sending out light, heat,
radio waves and other radiation until all the hydrogen is
used up. Medium – sized stars like our Sun burn for
about 10 billion years.
Hydrogen & the Hindenburg
Disaster (Fact or fallacy?)
Major Features of the Universe
cont- (DP 1)
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Nebulae are gigantic clouds in space they are made
up of dust and gas, often the remains of exploded
stars. Nebulae gather due to the effect of gravity.
Nebulaes are the beginning of stars. Nebulae some
times glow red as they are warmed by radiation from
nearby stars.
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Galaxies are clusters of stars. Our Sun forms part of
The Milky Way galaxy. The Milky Way can be seen
easily at night by the naked eye.
Major Features of the Universe
cont- (DP 1)
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A solar system is a system of planets or other
bodies orbiting another star (or sun), planets are held
in place by the stars gravitational effect.
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Our solar system consists of the Sun together with
the nine planets and all other celestial bodies that
orbit the Sun. Celestial bodies includes moons and
asteroids.
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The Sun is by far the most massive part of the solar
system, containing almost 99.9% of the system's total
mass.
Planets of our solar system
(In order of distance from the Sun) DP 3
Planet
AUs from Sun
Characteristics
Mercury
0.4
Small rocky planet with atmosphere (0 moons)
Venus
0.7
Small rocky planet with atmosphere (0 moons)
Earth
1.0
Small rocky planet with atmosphere & with one moon.
Presence of liquid water & optimum distance from sun to
support life (one moon)
Mars
1.5
Small rocky planet with atmosphere (two moons)
Jupiter
5.2
Largest planet mostly gas (rock core & 18 moons+)
Saturn
9.5
Second Largest mostly gas planet (rock core & 18 moons)
Uranus
19.2
Large mostly gas & liquid methane planet (15 moons)
Neptune 30.1
Large mostly gas & liquid methane planet (2 moons)
Pluto
Smallest planet, rocky with (1 moon)
39.5
Planets in the nights sky
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The word planet is derived from the Greek
word planetes which means ‘wanderer’.
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This is because if you observe planets such as
Mars or Mercury they will appear to wander
rather than just rotate their position. This is due
to their differing orbits around the Sun.
Mnemonic for planets of solar
system
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"My Very Excellent Mother Just Sent Us Nine
Pizzas"
Size of Planets
.
The asteroid belt DP 4
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A belt of asteroids (minor planets made of rock
and metal) lies between Mars and Jupiter.
These objects all orbit the sun in roughly
circular orbits that lie in the same plane, the
ecliptic (Pluto is an exception; it has an
elliptical orbit tilted over 17° from the ecliptic).
Ptolemy’s & Copernicus – Kepler
Models of the Universe DP 6
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Ptolemy (130AD) believed the Earth was the
centre of the Universe
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Nicolaus Copernicus (1512) relised that the
Sun and not the Earth was the centre of the
Universe. This model was confirmed in 1609
by Johannes Kepler
Planet Structure
The ‘solid planets’ (terrestrial)
The first four planets are made primarily of rock Mercury, Venus, Earth and Mars. (Pluto is also
made of rock)
The ‘gas planets’ (non-terrestrial)
The next four are the ‘gas giants’ – Jupiter, Saturn,
Uranus and Neptune
Satelites
What is a satellite?
An object in an orbit is called a satellite. A satellite can be natural, like the Moon,
or human-made (or even perhaps extraterrestrial?). Satellites can travel around
planets or around stars such as our Sun.
All the planets are satellites around the Sun. Almost every ship launched from
Earth can be considered a satellite, as it is orbiting either the Earth or the Sun.
Temperatures on the Planets
Generally, the farther from the Sun, the cooler the planet.
Differences occur when the greenhouse effect warms a planet (like
Venus) surrounded by a thick atmosphere.
Planet Density
The outer, gaseous planets are much less dense than the
inner, rocky planets.
The Earth is the densest planet. Saturn is the least dense
planet; it would float on water.
The Mass of the Planets
Jupiter is by far the most massive planet; Saturn trails it. Uranus,
Neptune, Earth, Venus, Mars, and Pluto are orders of magnitude less
massive
Gravitational Forces on the Planets
The planet with the strongest gravitational attraction at its surface is
Jupiter. Although Saturn, Uranus, and Neptune are also very massive
planets, their gravitational forces are about the same as Earth. This is
because the gravitational force a planet exerts upon an object at the
planet's surface is proportional to its mass and to the inverse of the
planet's radius squared.
Asteroids & Asteroid Belts DP 4
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Asteroids are basically chunks of rock.
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An Asteroid belt is as the name suggests a belt
of asteroids. The asteroid belt we refer to (in
our solar system) is the region of interplanetary
space between Mars and Jupiter where most
asteroids are found.
Rotation = Day and Night DP 5
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The rotation of the Earth on its axis gives us day and night.
Costellations DP 8
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Historically, constellations were groupings of stars
that were thought to outline the shape of
something, usually with mythological significance.
There are 88 recognized constellations, with their
names tracing as far back as Mesopotamia, 5000
years ago. Constellations are still used today by
modern astronomers to assist in mapping out
space and giving a reference point for locating
planets.
Constellations and the Zodiac DP 8
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The ancient astronomers associated dates with the
constellations (in a narrow belt known as the zodiac) Twelve
zodiacal signs were named by the Ptolemy (2nd-century) as
follows: Aries (ram), Taurus (bull), Gemini (twins), Cancer
(crab), Leo (lion), Virgo (virgin), Libra (balance), Scorpio
(scorpion), Sagittarius (archer), Capricorn (goat), Aquarius
(water-bearer), and Pisces (fishes).
Celestial Sphere DP 9
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A celestial sphere is imaginery sphere surrounding
the earth. At any one time we see no more than half of
this sphere
East
West
South Celestial Pole – DP 10
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The SCP is the zenith for an observer standing
directly at the south pole
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The SCP can be located by using the Southern
Cross (see page 165)
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The stars can be observed to rotate around the
CSP I.e. as the Earth rotates on its axis (23.5)
Plotting Star Positions. Prac 5.2 p.163
Azimuth and elevation are angles used to define the
apparent position of an object in the sky, relative to a
specific observation point.
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The azimuth is the point of an object on the celestial
sphere
The elevation is the height / angle of the object above
the horizon
The zenith is the point straight overhead
Azimuth & Elevation DP 11
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Azimuth is the lateral measurement and
elevation (or altitude) is the perpendicular
measurement (see text p. 164)
Note: the Zenith is directly above the observer.
Phases of the Moon DP 13
Waxing, Waning
& Gibbous DP 13
Waning- Shrinking.
Waxing - Growing
Gibbous moon (swollen on one side) is between a
full moon and a half moon, or between a half moon
and a full moon.
Moon Facts
1.
Moon travels around the Earth in a circle called an orbit. It takes the moon about 28
days to go one time.
2.
The Moon is about 250,000 miles (384,400 kilometers) from Earth and has a diameter of
2,000 miles ( 3,476 kilometers).
3.
The Sun always lights up (illuminates) half of the Moon at one time.
4.
The Moon is not a light source, it has no light of its own. We can only see the moon
because it reflects light from the sun.
5.
The Moon appears to change shape but what we are actually seeing is the Moon lit up by
the light from the Sun in different ways on different days.
6.
We always see the same side of the moon. The Moon always keeps the same side
pointing towards us so we can never see the 'back' of the Moon from the Earth.
Even more Moon facts
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The Earth's Moon is the fifth largest in the whole solar system, and is bigger than
the planet Pluto. The Moon has a nearly circular orbit (e=0.05) which is tilted
about 5° to the plane of the Earth's orbit. Its average distance from the Earth is
384,400 km. The combination of the Moon's size and its distance from the Earth
causes the Moon to appear the same size in the sky as the Sun, which is one
reason we can have total solar eclipses. The Moon's orbital period is 27.322 days
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If the speed of light is about 300, 000Kms per sec how long then does it take for
reflected light from the the Moon to reach us? Just over 1 sec (1.3sec actually!)
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Do stars move? Yes like us (our entire solar system) they are rotating around the
centre of our galaxy. In relation to the size of the galaxy this movement is quite
slow.
What formed the Moon?
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The most popular theory is that the Moon was torn from the Earth
in a huge planetary collision about 4.5 billion years ago. An object
at least as large as Mars, it is proposed, crashed into Earth,
throwing vast clouds of debris into orbit. This then cooled and
coalesced under the influence of gravity to form the Moon.
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So far, the hypothesis is supported by data: it fits with the
evidence of lunar rocks and observations from spacecraft orbiting
the Moon. As the material that formed the Moon would have come
from the Earth’s crust and mantle, not its iron-rich core, the
relative lack of iron on the Moon is potentially explained
Moon Positions
Solar Eclipse DP 15
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A solar eclipse is when the moon obscures our view of the sun
(I.e. the Moon comes between Earth and the Sun)
Eclipses
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Eclipses occur more often than most people
realise with a solar eclipse taking place roughly
every 18 months. However, a total eclipse will
only be seen from any specific location on
Earth about once every 100 years. Last solar
eclipse in Australia was on the 16th Feb 1999.
Lunar eclipse DP 15
Seasons DP 16 & 17
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The Earth’s axis (23.45 degrees) is responsible for the seasons. It takes
365.26 days for the Earth to orbit the sun. The top diagram is of the
northern hemisphere and the lower diagram is of the southern
hemisphere. In the top diagram during winter where would Australia be
located?
Seasons contSummer night
Consider these diagrams!
Spring day
Elevation of Sun DP 16 cont
Due to its changing elevation and duration of
exposure on the Earths surface the Sun radiant
energy has differing seasonal effects on our
environment.
Date definitions – Solstice DP 18
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Summer solstice (22 Dec) On the day of Summer Solstice, the Earth’s south pole is tilted
towards the Sun. The Sun rises south of east, sets south of west and reaches 75 1/2° above
the horizon at noon. This is, usually, the longest day of the year.
Winter Solstice (22 June), Earth’s south pole is tilted away from the Sun. The Sun rises
north of east, sets north of west and reaches 281/2° above the horizon at noon. This is,
usually, the shortest day of the year.
Which of the diagrams below represents the winter solstice?
Dates Defined – Equinoxes DP 18
cont
There are two equinoxes each year – Spring (22 Sep) & Autumn (22 Mar). When simplified the term
simply refers to the two times of year when night and day are the same length.
On the day of the Spring and Autumn Equinoxes, the Earth’s poles are the same distance from the Sun.
The Sun rises due east, sets due west and gets to 52° above the horizon at noon. On both days there are
roughly 12 hrs of day and 12 hrs of night.
Does the diagram below represent both equinoxes?