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CHAPTER 9: STARS & GALAXIES
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9.1 The Sun
Characteristics of the sun
(a) SizeIts diameter is about 109 times
the diameter of the Earth (1.4million km)
(b) MassAbout 333420 times the massof the Earth(1.989 x 1030kg)
(c) DensityAbout the density of the
Earth(1.41 g cm -3)
(d) Surface temperatureRanges from
5000 oC to 6000 oC
(e) Temperature of Suns core 15 million oC
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The structure of the sun(a) Corona
- The outermost layer of Suns atmosphere
(b) Photosphere
- The layer of dense gas that appear yellow from the
earth.
- Sunspots, prominences & flares occur on this surface
(c) Chromosphere
- The Suns atmosphere (in between the photosphere &the corona)
- The layer of gas below the corona that is bright red in
colour.
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The structure of the sun(d) Core
- Consists of hydrogenand heliumgases.
- Nuclear reactions occur to generate heat and lightenergy
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Phenomena On The Surface Of The Sun
Sunspots
- Dark spot on the photosphereProminences
- Hot gas that shoots out from the chromosphere. These gasexplosions produce a very bright light.
Solar Flares- Explosion of gas that occur suddenly in the chromosphere
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Prominence and solar flare
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Sunspot
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9.2 Stars & Galaxies In The Universe
A stara ball of very hot gaseswhich produces its own heat
& lightStars have various types based on their brightness, colour,size & temperature.
The stars with the highest temperature (blue) & with the
lowest temperature (red)Rigel is a blue supergiant star
Stars that are smaller than the Sun - white
dwarfs.
Stars that are larger than the Sun
giants/redgiants
The largest giants supergiants
Stars can be classified according to their sizes as shown:
White dwarf, the Sun, giant star, supergiants ( + in size)
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The colour of a star in relation to its surface temperature
Colour Surface Temperature (oC) Examples
Blue Above 30000 Zeta Puppis
Blue-white 1500030000 Rigel
White 800011000 Vega
White-yellow About 7500 Canopus
Yellow About 6000 SunOrange About 5000 Aldeberan
Red About 3500 Betelgeuse
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Formation & Death Of Stars Stars come into existence in the vast clouds of dust &
gascalled nebulas that move through space.
A star begins to form when a large number of gasparticles whirl together.
The weak gravitational forceof the whirling particlesattracts more particles.
As the group of particles slowly gets larger & larger,
the gravitational force gets stronger & stronger. The particles draw in towards one another & form a
ball of gas.
As the number of gas particles in the ball grows larger,pressure builds up inside the ball.
Finally, the pressure becomes strong enough to raisethe temperature of the gases & the gases begin toglow.
When the pressure & temperature inside the ball getvery high, nuclear reaction begins to take place. The
gases become a star.
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oC
Galaxies
Types of galaxies
Elliptical
galaxies
-Contains
mostly stars
-Vary in size
-Smaller than
spirals
-E.g The M87
galaxy
Spiral
galaxies-The most
numerous form
among the larger
galaxies
-Contains stars,
dust & gas
-E.g The Milky
Way & the
Andromeda
Irregular
galaxies
-Appear to have
no special
shape at all
-Contains stars,dust & gas
-E.g The
Magellanic &
cloud
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9.3 Thankful For The Existence Of The
Universe As A Gift From God
We should appreciate the uniqueness,order, beauty & harmony in the universe as
a sign of the glory of God.
The universe is constantly expanding &
getting bigger all the time.
All that exists in the universe is not
permanent but changes with time.
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The Importance Of
The Sun To Life In
The Earth
The sun
supplies light
energy to
green plantsto make food
The Sun supplies heat energy to warm
the Earth & provide a suitable
temperature for living things
Heat from the Sun enables
evaporation & condensationprocesses to take place
which will lead to the
occurance of rain
The Sun supplies lightenergy that enables
humans & animals to see
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