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Boardworks GCSE Science: Physics The Universe

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Presentation on theme: "Boardworks GCSE Science: Physics The Universe"— Presentation transcript:

1 Boardworks GCSE Science: Physics The Universe

2 What determines how long you will live?
HUMAN LIFE EXPECTANCY What determines how long you will live? Why do some people grow to be 100 years old and some only live to be 50 years old? What factors affect your everyday life expectancy?

3 Star Life Expectancy The “life expectancy” of a star depends on the star’s MASS. Which star below would you expect to live longer? Why? What are some similarities between a star’s life expectancy and a human’s life expectancy?

4 Boardworks High School Science The Life Cycle of Stars
The Birth of a Star Boardworks High School Science The Life Cycle of Stars Teacher notes This slide aims to provide an overview of the process of star formation. Once the fusion process begins in the core it is no longer called a protostar, but a main sequence, or stable star.

5 Boardworks High School Science The Life Cycle of Stars
The Birth of a Star Boardworks High School Science The Life Cycle of Stars When the temperature in the core of a protostar reaches roughly 15 million oC, nuclear fusion begins and a stable star is born. The star now enters its stable phase and is called a main sequence star. A star is stable when its size remains constant over time. All stars have a stable period in their lives, the length of which is determined by their mass. Photo credit: NASA

6 Stars are born in a nebula, or cloud of gas and dust

7 The left pillar is approximately 4 ly in length.
Pillars of Creation Part of the Eagle Nebula, 7,000 ly from Earth, where many stars are forming The left pillar is approximately 4 ly in length.

8 Boardworks GCSE Science: Physics The Universe
Nuclear Fusion Boardworks GCSE Science: Physics The Universe A main-sequence star is ‘powered’ by nuclear fusion reactions taking place in its core. Nuclear fusion involves light atomic nuclei joining together (fusing) to form heavier ones. This process releases huge amounts of energy. Each second, the Sun produces 400,000,000,000,000,000,000,000,000 watts of energy! Photo credit: © 2006 Jupiterimages Corporation It would take 2,000 million nuclear power plants a whole year to produce the same amount of energy on Earth. In the Sun and most stars, hydrogen atoms fuse together to form helium. This provides the energy for life on Earth.

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10 Boardworks GCSE Science: Physics The Universe
Using nuclear fusion Boardworks GCSE Science: Physics The Universe Teacher notes This two-stage sequence explains the steps in nuclear fusion.

11 What makes a star stable?
Boardworks High School Science The Life Cycle of Stars Inside a star, the energy released by fusion produces an outward acting force. This causes star expansion. However, the star’s huge mass means that gravity is acting in the opposite direction, forcing particles towards the core. explosive force of fusion gravitational force 332,948 Earth masses Teacher notes Students should recall the details of the fusion process, remembering particularly that isotopes of hydrogen are required to produce helium. If these two forces are equal, then the star will not change its size. It is said to be stable.

12 Boardworks High School Science The Life Cycle of Stars
The Stable Phase Boardworks High School Science The Life Cycle of Stars Stars live the majority of their lives in this stable phase (a balancing act between gravity pulling fuel down to the core, and heat trying to expand it outward). In this phase, stars give off energy and heat, and as a result, change color. Our sun is about halfway through its 10 billion year stable phase. Protostars that never get large enough for fusion to begin become BROWN DWARVES. Material left over after the star forms becomes planets, asteroids, comets, etc. Photo credit: NASA

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14 Boardworks High School Science The Life Cycle of Stars
Stable star structure Boardworks High School Science The Life Cycle of Stars

15 Boardworks High School Science The Life Cycle of Stars
The end of stability Boardworks High School Science The Life Cycle of Stars A star’s stable phase ends when most of its hydrogen has been consumed by fusion. The star enters it’s old age. The reduced fusion causes the core to cool, lowering pressure causing the star to collapse upon itself under its own gravity. As the outer layers contract, they heat up. This triggers the fusion of the remaining hydrogen. The increased energy output in the outer layers causes them to expand. Photo credit: NASA The star increases massively in size, becoming a red giant.

16 What happens in the core?
Boardworks High School Science The Life Cycle of Stars The core continues to contract. This causes it to reach new extremes of temperature (over 100 million Kelvin) and pressure. This gives helium atoms enough energy to fuse. Thus heavier atoms, such as carbon and oxygen, are produced. In the largest stars elements as heavy as iron can be produced. However such large stars will suffer a different fate to the Sun. Photo credit: NASA

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The death of a star Boardworks High School Science The Life Cycle of Stars

18 Boardworks GCSE Science: Physics The Universe
What is a white dwarf? Boardworks GCSE Science: Physics The Universe A white dwarf is formed at the end of the life cycle of a star that is about the same size as the Sun. The outer layers of the star are ejected away from the white dwarf core and form a planetary nebula This photograph was taken with the Hubble Space Telescope and shows ancient white dwarf stars in the Milky Way. Photo credit: NASA and H. Richer (University of British Columbia) The white dwarf stars are shown ringed in blue.

19 Boardworks High School Science The Life Cycle of Stars
Red supergiants Boardworks High School Science The Life Cycle of Stars Teacher notes Students may wish to carry out their own research into supernovas, black holes and neutron stars.

20 Boardworks GCSE Science: Physics The Universe
What is a supernova? Boardworks GCSE Science: Physics The Universe Teacher notes This seven-stage animation explains what a supernova is and the stages in its formation.

21 Boardworks GCSE Science: Physics The Universe
How are elements made? Boardworks GCSE Science: Physics The Universe Nuclear fusion in stars produces new atoms. In the early stages of a star’s life, light elements such as helium are mainly formed. When all the hydrogen has been used up, other elements are fused together to make the heavier elements of the periodic table. Photo credit: NASA Headquarters - Greatest Images of NASA (NASA-HQ-GRIN) The Ring Nebula as imaged by the Hubble Space Telescope. The nebula is around one light year in diameter and is 2,000 light years from Earth. The blue areas of the nebula show the presence of superheated helium gas clouds, and the red and green areas show ionized oxygen and nitrogen. However, not all elements are made in the early stages of a star’s life. Some of the heavier elements are only made when a massive star explodes in a supernova at the end of its life.

22 Boardworks GCSE Science: Physics The Universe
What is a Neutron Star? Boardworks GCSE Science: Physics The Universe After a supernova the core of a of star more than 8 times the size of the Sun becomes a Neutron Star. A neutron star is so dense that on Earth 1 tsp would weigh 1 billion tons! Photo credit: NASA Headquarters - Greatest Images of NASA (NASA-HQ-GRIN) The Ring Nebula as imaged by the Hubble Space Telescope. The nebula is around one light year in diameter and is 2,000 light years from Earth. The blue areas of the nebula show the presence of superheated helium gas clouds, and the red and green areas show ionized oxygen and nitrogen. This is a baby neutron star in the remains of a supernova.

23 How are black holes formed?
Boardworks GCSE Science: Physics The Universe The end of the life cycle of really massive stars is different to that of massive stars. After a really massive red giant collapses in a supernova explosion, it leaves an object so dense that nothing, not even light, can escape its gravitational pull. This is called a black hole. Some scientists believe that there are black holes at the centre of galaxies. Photo credit: NASA Headquarters - Greatest Images of NASA (NASA-HQ-GRIN) The spiral galaxy NGC 4414 as imaged by the Hubble Space Telescope. The core of the galaxy contains mainly older yellow and red stars. The outer spiral arms contain young, blue stars. The outward spiralling arms of the galaxy are very rich in interstellar dust. If light cannot escape from a black hole, then how can a black hole be observed?

24 How can a black hole be ‘seen’?
Boardworks GCSE Science: Physics The Universe Teacher notes This three-stage animation explains how we know black holes exist, and where, even though they cannot be seen.

25 How do stars begin and end
Boardworks GCSE Science: Physics The Universe Teacher notes This animation introduces how stars are formed, and how small, massive and really massive stars die.

26 Lifecycle of small stars
Boardworks GCSE Science: Physics The Universe Teacher notes This ordering activity could be used as a plenary or revision exercise on the lifecycle of small stars, and the difference between small stars and large stars in the following activity. Mini-whiteboards could be used to make this a whole-class exercise.

27 Lifecycle of large stars
Boardworks GCSE Science: Physics The Universe Teacher notes This ordering activity could be used as a plenary or revision exercise on the lifecycle of large stars, and the difference between large stars and small stars in the previous activity. Mini-whiteboards could be used to make this a whole-class exercise.

28 Terms about the lifecycle of stars
Boardworks GCSE Science: Physics The Universe Teacher notes This matching activity could be used as a plenary or revision exercise on the lifecycle of stars. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.

29 Boardworks GCSE Science: Physics The Universe
Star Life Cycle Boardworks GCSE Science: Physics The Universe

30 Boardworks GCSE Science: Physics The Universe
Questions about stars Boardworks GCSE Science: Physics The Universe 1. What two elements make up most of the Sun? hydrogen and helium 2. What is a nebula? A huge cloud of gas and dust from which a star is born. 3. What process has allowed the Sun to emit light and heat energy over thousands of million of years? nuclear fusion 4. Which is the most dense, a white dwarf or a neutron star? neutron star 5. What is the fate of a star similar to the Sun? the Sun  red giant  white dwarf


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