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Contents
Chapter 9: Star
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Chapter 9: Stars and Galaxies
i) The Sun..
- the centre of our solar system
- The Sun is actually a star of moderate size
- The Sun takes 25 and half days to rotate on its axis
from west to east
Photograph 9.1: The Sun
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30
Characteristics of
The Sun
Measurement
Size ( diameter) 1.4 million kmMass 1.989 x 10 kg
Density 1.41 g cm ( compared with density of
water )
Surface temperature 6000 degree Celsius
Temperature of Suns
Core
15 million degree Celsius
Table 9.1: Characteristics of the Sun
Notes:
- The Suns diameter is 109 times the diameter of the
Earth
- The Suns mass is 330 thousand times the mass of the
Earth
- The density of the material that forms the sun is one
over four times that of the Earth
Structure of the Sun..
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Figure 9.1: The structure of the Sun
The Suns atmosphere consists of three parts. The parts are,
i) corona
ii) chromosphere
iii) photosphere
Characteristic of
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Corona
- outer most layer of gas in the Suns atmosphere
- corona forms a circle of white light around the Sun
- only visible during eclipse of the Sun
- temperature is about 1.5 million degree Celsius
Chromosphere
- bright red layer of gas below the corona
- only visible during eclipse of the Sun just like the
corona
- temperature varies between 10 000 and 500 000 degree
Celsius
Photosphere.
- compact layer of gas seen to be shining with yellow
light from Earth
- Photospheres surface appears turbulent because gas from
the Suns core is release to its surface
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- This layer is responsible for radiating heat and light
from the Sun
Suns Core
- consist of hydrogen and helium gases
- nuclear reaction occurs in the core all the time to
generate and release heat and light energy
- The cores temperature is extremely high. Its about 15
million degree Celsius
Photograph 9.2: corona and chromosphere can only be seen
during an eclipse of the Sun
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Phenomena of that occur at the Suns
atmosphere
Few of phenomena that occur at the Suns atmosphere are
i) prominences
ii) Solar flares
iii) Sunspots
Figure 9.2: Figure above shown prominence, solar flare
and sunspot
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Phenomena Descriptions
Prominence
- an explosion of hot gas that shoots out from
the Suns chromosphere with shiny bright
light
- can been seen near the edge of the Sun
during an eclipse of the Sun
- prominence emits charged particles and
ultraviolet rays into outer space
Solar layer
- a strong explosion of gases that happen
suddenly into outer space
- also emit rays like gamma rays and X-rays
- this phenomena occurs for only a few
minutes or a few hours but it release a great
deal of energy
Sunspot- dark spots on the surface of the Suns
Photosphere
- has a lower temperature ( 4000 degree
Celsius ) than its surroundings ( 6000 degree
Celsius )
Table 9.2: Description of phenomena of that occur at the Suns
atmosphere
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The effect of the phenomena on the surface
of the Sun on Earth
- charged particles as a result of solar flares reach the North Pole or the
South Pole of the Earth and collide with gas molecules in the atmosphere
- as a result, colorful light that consist of green, yellow and red lights are
produced. These light that can be seen at night are called aurora
- the charged particles and radiation from the Sun like cosmic rays, X-rays
and gamma rays will collide with particles in the Earths atmosphere
- this causes disturbance to the communications system like television and
radio broadcast, telegraph transmissions and telephone calls.
Photograph 9.3: Aurora that happen on Earth
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Generation of energy by the Sun
- consist of hydrogen and helium gases
- nuclear reaction that takes place in the Suns core
generates energy
- during a nuclear reaction, 2 hydrogen atoms fuse to
form one helium atom. Heat and light energy are
released
Figure 9.3: Nuclear reaction that occur in the Suns core
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Stars and Galaxies in the Universe
Star is
- a natural object in outer space that can release heat and
light energy
- generates energy through nuclear reactions
Sun is
- a star that is nearest to Earth
Distance of a star from the Earth is measured in units of
light year, distance traveled by light in a year. There are
bright stars in the sky can been seen by naked eye at night
such as the Sirius and Rigel.
Science Corridor:
- Alpha Proxima is the second nearest star to earth. This star is situated about 4.2
light years from Earth
- Sirius and Rigel are situated 8.6 and 900 light years respectivelyfrom Earth
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Classification of stars
Stars need to be classified to facilitate research and classified
according to characteristics such as
i) temperature
ii) size
iii) brightness
A star with very lo temperature is red in colour. A star that very hot
is blue in colour.
Dwarf star - very small star, smaller than Earth
Giant star - tens of times bigger than the Sun
Supergiant star - very big star, 100 times bigger than the
Sun
Apparent magnitude - measurement of the brightness of object in the
sky that can be seen from Earth. The lower the magnitude value, the
brighter the object
Figure 9.4: Apparent magnitude reading
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Birth and death of star
Star - born from nebula
Nebula -
- a large cloud that consist of dust and gases
- gases and particles in the nebula are pulled by strong
gravitational force to form a lump and causes the
lump of gases to shirk and is compressed until it
becomes very compact to form a core
- when temperature and pressure in the core become very
high, nuclear reaction occurs and hydrogen gas is turned
into helium. A lot of heat and light energy are released
the, the core shines and a star is born.
The star will die when all hydrogen gas in its core is used
up in nuclear reaction.
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The star will undergo death in by following stages with
A star of moderate size like Sun:
1. the hydrogen atoms in the star are used up and nuclear
reaction stops
2. the star expands because its gravitational force has
decreased and forms a red giant
3. the outer parts of the star drift out into space leaving
the extremely hot white core called the white dwarf
4. the with dwarf is a star that is dense, compact and
becoming increasingly cold
5. the, its continues to become colder and eventually leaves
a black body or black dwarf (looks dark in outer space)
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A star that is bigger than the Sun:
1. the outer layer of the star expands as a result of
decreasing gravitational force to form a red giant
2. it continues to expand and finally explodes as
supernova. A great deal of heat and light energy are
produced
3. very strong gravitational force in the core of the star
converts it into either a neutron star or black hole.
Black hole - an object that is very dense and has strong
gravitational force that pulls all surrounding materials,
including light, that is close by, to it. Black hole also cant
be seen in outer space.
Neutron star - a very small and dense star as it consist
mainly of neutron particles.
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Constellation
Constellation
- a group of stars that forms a certain pattern
in the sky
- in ancient times, knowledge of the constellation were
used as a calendar and compass
Figure 9.5: Example of constellations
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Types of galaxy
Classified according to:
- elliptical galaxies
- spiral galaxies
- irregular galaxies
Shape of galaxy Example of galaxy
Elliptical Galaxy M87 in Virgo
Spiral Milky Way and Andromeda
Irregular Magellan Cloud
Table 9.3: Shows the shape and example of galaxy
- our solar is in a galaxy called the Milky Way.
- The Sun is one of the millions of stars in the Milky
Way.
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iii) Existence of the Universe as a Gift
from God
Many scientist believe in the theory that the Universe begins
with a huge explosion, the Big Bang. During the explosion,
the Universe expanded from nothing to become a huge space
measuring 2 billion billion kilometers in width, in a single
second.
At present, scientists still cant explain why the Big
Bang occur. We should appreciate the uniqueness, orderliness,
beauty and harmony in the Universe as a sing Of the glory
of God.
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Questions
i) The distance of stars from Earth is measured in units
of ______________.
ii) The _____________ is the nearest star to Earth
iii) Sirius and Rigel are examples of ________ stars in
the sky.
iv) Stars produce energy through __________________.
v) A very hot star is _______ in colour while a very
cold star is ________ in colour.
vi) _________ are natural objects in outer space that
release heat and light energy.
vii) A ______ is a group of stars that form a certain
pattern in the sky.
viii) In ancient times, constellations were used as _____
and ______
ix) ________ which is our solar system found.
x) _______ is the beginning stage in the death of a star.
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Chapter 10: Space Exploration
Development in the field of astronomy
and space exploration
Astronomy - is the field of study about natural objects in the
sky
Photograph 10.1: Galileo Galilei Photograph: 10.2 Isaac Newton
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Development in space exploration
Space exploration is the investigation of the Universe beyond
the atmosphere of the Earth by using spacecraft. Space
exploration was first done from Earth with the use of a
telescope.
Rockets, man-made satellites, space stations and space
shuttles were later invented to continue the efforts of space
exploration.
Photograph 10.3: a spacecraft Photograph 10.4: Measat 3
is heading
to space
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Year Development
1957 The worlds first artificial satellite, Sputnik 1, was
launched. Four months later, Sputnik 2, carrying adog named Laika was launched
1961 Yuri Gagarin became the first person to orbit theEarth
1969 Man first landed on the Earth
1981 The first reusable names spacecraft, the SpaceShuttle, was launched
Table 10.1: Some of the development in space exploration
Photograph 10.5: Man has successfully landed on the surface of the Moon.
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Application of technology related to pace
exploration and astronomyA few types of modern technological instruments have been inverted
for outer space exploration. Among them are the:
- telescope
- spaceship
Telescope are three types of telescope used for outer space
exploration:
- refracting telescope
- reflecting telescope
- radio telescope
Refracting telescope - uses lens while reflecting telescope uses mirrors
to take and send photographs on outer space.
Radio telescope - used to received electric signals and radiation from
outer space.
Spaceships have been launched into outer space to obtain various
information. Spaceships that carry astronauts are launched by rockets
into outer space but probe is a spaceship that doesnt carry humans.
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Questions
i) Who said that the Earths orbit is elliptical in
shape?
ii) Who is invented the first astronomical telescope?
iii) Who introduced the law of gravity?
iv) Who suggested that the Earth was the centre of
the solar system?
v) Who suggested that the Earth rotates on its axis?
vi) Who suggested that the Sun is the centre of the
solar?
vii) Who is the first person to walk on the Moon?
viii) Who discovered Halleys Comet?
ix) Who advanced the idea about the relationship
between time, space and energy?
x) Who discovered Pluto?
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