Density: about

1500 kg/m3

Diameter: about

1 400 00 km = 100 x the

Earth diameter

Mass: 1.99 x

1030 kg

Temperature: Surface-6000C Centre of the

Sun- 15 000 000C

Produces a strong gravitational forces:

about 28 times greater than the

gravitational force produces by the

Earth

•  Middle layer •  Can only be

seen during an eclipse

•  The temperature about 15 000°C

•  Outermost layer

•  Extends hundreds of km from the centre of the Sun

•  The temperature can reach 2 000 000°C

•  Surface of the Sun

•  About 500km thick

•  Consists of dense gases

•  The temperature is about 6000C

Prominences Throw out matter from the Sun into space at speeds from 600km/s to more than 1000km/s Last for a few days or even for a few month

Sunspots ü Dark areas on the Suns ü Cooler than the surrounding areas ü May last for more than a week

Solar Flares ü  violent and spectaculars gas explosion that often occurs near sunspots ü  made up of numerous charged gaseous particles from the Sun shooting outward at high speed into outer space ü  interact with Earth’s magnetic field producing dazzling light display called aurora

Aurora Borealis, (northern

light)

Aurora Australis, (southern

light)

q Composition of Sun is helium and hydrogen

q Because of the temperature, thermonuclear reactions occur in the Sun’s core

q Release large amount of heat and light energy

q Temperature reach 15 000 000 °C

q Energy from the core is distributed by the processes of radiation and convection

q Sun energy is emitted as electromagnetic waves

Star with

mass <1.4 x Sun’s mass

Star with

mass >3 x

Sun’s mass

Star with mass 1.4 to 3.0 x

Sun’s mass

•  The diagram above shows the formation and death of stars •  Stars begin as a large cloud of gas and dust called nebula •  After ten thousands of year collapse, a hot core will be formed •  When the supply of gas in a star runs out, the star dies

•  When a star with a mass of up to 1.4 times the Sun’s mass, it will become a red giant •  The red giants then contracts, releasing its gas and turns into white dwarf

•  When a star with mass of between 1.4 and 3.0 times the Sun’s mass, it will become red giant then continues swell even more to become supergiant •  The supergiant then explodes producing supernova •  As the supernova collapse, a neutron star is formed

•  When a star with mass of more than 3.0 times the Sun’s mass, it swell up become red giant then become supergiant •  The supergiant then explodes producing supernova •  As the supernova collapse, its core becomes so massive that its gravity sucks everything including light into it •  The core is called a black hole

•  Stars are grouped together in vast collections called galaxies

•  Our Solar System with only one star, the Sun, forms a tiny part of galaxy called

the Milky Way •  Galaxy are classified into various type

based on the shaped. •  Three common types of galaxies are

spiral, elliptical and irregular shaped

•  Large galaxy with 20k to 100k light years of diameter •  Disc-shaped with •  @ centre : older stars •  @ spiral arms :

•  new stars, •  Gases and dust •  30% of galaxies are spiral

•  Diameter of galaxy is 3k to 10k light years •  Smooth & rounded / oval in shape •  Brightest at the centre & fades towards the edge •  Consists of mainly old star •  60% of galaxies are elliptical

•  Diameter of this galaxy is 25k to 32k light years •  No definite shape & exists in various forms •  Consists of bluish- white stars (young star) & nebulae •  10% of galaxies are irregular

•  A spiral-shaped galaxy with a diameter of 100k light years & is about 10k light years thick

•  Consists of old stars at the centre at the center & nebulae (dust and gases) at spiral arms

•  Stars in Milky Way galaxy are so close together & observed as hazy patches

•  The Sun is 30k light years from the center of Milky Way

•  The Sun takes 200 million years to orbit the centre of the Milky Way

Main Source of Energy

Sunlight is essential for photosynthesis

Causes water to evaporate •  produces rain

Calendars based on phases of the Moon

Affect the occurance of ocean tidal

Encourage the development of technologies based on the Moon travelling

•  Nobody knows exactly how the Universe began or how it will end.

•  Among the various scientific theories about the formation of the Universe, the most widely accepted scientific theory is the Big Bang theory

•  According to the Big Bang theory, about 12 billion to 15 billion years ago, our Universe began with enormous explosion. Since then, the Universe has forever been expanding everywhere at the same time