chapter9-stars and galaxies

8/11/2019 Chapter9-Stars and Galaxies

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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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