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Life cycle of stars. - PowerPoint PPT Presentation
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Life cycle of stars
• During the collapse, the material heats up by frictional processes and begins to radiate infra-red radiation so astronomers are hoping to detect this to confirm the formation process. This is very difficult because the protostar would have a lot of gas and dust still surrounding it (a Bok Globule).• Stars are formed in groups as the different parts of the original nebula collapse.
Travelling at the speed of light (or radio wave)300,000 km /sec
8 minutes
6 hours
4 years
sun
nearest star
pluto
100,000 light years
100 billion stars
Milky way galaxyAndromeda galaxy
Our sun is one of millions of stars in a group of stars called a galaxy
100,000 light years
100 billion stars
Light from our nearest galaxy has taken 2 million years to reach us!
Milky way galaxyAndromeda galaxy
Our sun is one of millions of stars in a group of stars called a galaxy
BIRTH OF A STAR
* A star forms from a huge cloud of dust and gas.
* Gravity slowly pulls the material together.
* Rocks crash into each other and heat up.
Our sun 4,500 million years ago.
• During the collapse, the material heats up by frictional processes and begins to radiate infra-red radiation so astronomers are hoping to detect this to confirm the formation process.
BIRTH OF A STAR
* A star forms from a huge cloud of dust and gas.
* Gravity slowly pulls the material together.
* Rocks crash into each other and heat up.
Our sun 4,500 million years ago.
* Nuclear reactions begin and the star starts to shine.
Our sun 4,500 million years ago.
BIRTH OF A STAR
Planets are natural satellites
of the sun * Smaller masses cool to form planets which orbit the sun under gravity.
* During a star’s life time, nuclei of lighter elements (mainly hydrogen and helium ) fuse to produce nuclei of heavier elements
* Nuclear reactions begin and the star starts to shine.
THE HERTZSPRUNG - RUSSELL DIAGRAM
LIGHT
INTENSITY
Wave length of light emittedBlue Red
HOT Cold
Newly formed stars join the ‘main sequence’at a point on the graph that relates to its mass.
THE STABLE LIFE OF A STAR
THE STABLE LIFE OF A STAR
THE STABLE LIFE OF A STAR
- Our sun stays on main sequence for 10 billion years
- If star mass is 15 x suns mass
then 10 million years.
Stars of greater mass than our sun (have higher core temperatures)can fuse heavier elements up to iron releasing even more energy.
Dark matter (ash)
Super nova
Explosionfusing heaviestknown elementseg 92U
Explosionfusing heaviestknown elementseg 92UalsoNew young starsand condensing
planets may form
Neutron star:p + e n v. dense !
Neutron star:p + e n v. dense !
For very massive stars, the material is so dense,the force of gravity so strong , that light itself cannot escape.
Nebular
Protostar Main Sequence
star
Red giantWhite dwarf
P3 4.2 The life history of a star similar in size to our sun
Protostar Gravity draws atoms together, releasing energy star heats up but does not shine,
Gravity draws atoms together, releasing energy Nebular
The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity.
Star
Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red.
White dwarf Fusion stops, gravitational collapse occurs, star heats up and changescolour from red to yellow to white. It finally becomes cold dark matter.
Nebular
Protostar Main Sequence
star
Red giantWhite dwarf
P3 4.2 The life history of a star similar in size to our sun
Protostar Gravity draws atoms together, releasing energy star heats up but does not shine,
Gravity draws atoms together, releasing energy Nebular
The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity.
Star
Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red.
White dwarf Fusion stops, gravitational collapse occurs, star heats up and changescolour from red to yellow to white. It finally becomes cold dark matter.
Nebular
Protostar Main Sequence
star
Red giantWhite dwarf
P3 4.2 The life history of a star similar in size to our sun
Protostar Gravity draws atoms together, releasing energy star heats up but does not shine,
Gravity draws atoms together, releasing energy Nebular
The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity.
Star
Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red.
White dwarf Fusion stops, gravitational collapse occurs, star heats up and changescolour from red to yellow to white. It finally becomes cold dark matter.
Nebular
Protostar Main Sequence
star
Red giantWhite dwarf
P3 4.2 The life history of a star similar in size to our sun
Protostar Gravity draws atoms together, releasing energy star heats up but does not shine,
Gravity draws atoms together, releasing energy Nebular
The star shines during fusion of hydrogen to helium for billions of years; outward radiation pressure is balanced by inward pull of gravity.
Star
Red giant Most of Hydrogen has been used, now helium fuses to make carbon, unused hydrogen is ejected to the surface, cools and appears red.
White dwarf Fusion stops, gravitational collapse occurs, star heats up and changescolour from red to yellow to white. It finally becomes cold dark matter.
Nebular
Protostar massivestar Super red
giantSuper nova
P3 4.2 The life history of a star several times larger than our sun
The explosion compresses the core into very densely packed neutrons. If the original star was more massive a black hole would be created. (The gravitational field is so strong that not even light can escape from it.)
Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. After further collapse it explodes as a supernova! (Outshines a galaxy for several weeks)
Neutron Star:
Super Nova:
White dwarf
Nebular
Protostar massivestar Super red
giantSuper nova
P3 4.2 The life history of a star several times larger than our sun
The explosion compresses the core into very densely packed neutrons. If the original star was more massive a black hole would be created. (The gravitational field is so strong that not even light can escape from it.)
Neutron Star:
Fusion stops, gravitational collapse occurs, star heats up and changes colour from red to yellow to white. After further collapse it explodes as a supernova! (Outshines a galaxy for several weeks)
Super Nova:
White dwarf
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