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The force of the spinning shaped the globule into a central core surrounded by a disk of gas and dust. Eventually, the core became the Sun and the material in the disk formed. the planets and asteroids of the Solar System. How was the Solar System formed?.
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The force of the spinning shaped the globule into a central core surrounded by a disk of gas and dust. Eventually, the core became the Sun and the material in the disk formed the planets and asteroids of the Solar System. How was the Solar System formed? The Solar System is about 4,600 million years old. It was formed from a nebula – an enormous cloud of dust and gas created when a dying star exploded. When shockwaves from other dying stars hit the nebula, it collapsed and formed a globule. Over millions of years, the temperature rose and the globule became more compressed, causing it to start spinning.
What makes up the Solar System? The Solar System is made up of various celestial objects: • the Sun • the planets • moons • asteroids • comets. Which of these objects are light sources? The Sun is a star and a light source. It is a massive ball of hot glowing gas, which gives out huge amounts of heat and light energy.
What is the Sun? The Sun is the star at the centre of the Solar System, about 150 million kilometres from Earth. The Sun mostly consists of hydrogen and helium. Its mass accounts formore than 99% of the total mass of the Solar System. Scientists used to think that chemical reactionspoweredthe Sun, but this could not explain how it had managed to stay ‘burning’ for millions of years. It is now known that nuclear fusion is the process that releases the Sun’s energy.
What are comets? The planets travel around the Sun in near-circular orbits. Comets are celestial objects that also travel around the Sun, but in very elliptical orbits. The head of a comet is a lump of ice and dust, a few kilometres in diameter. For most of its orbit, a comet is a long way from the Sun. The tail of the comet only appears when the its orbit passes nearest the Sun. The tail consists of gas and dust that are released from the comet by the heat of the Sun.
What powers a star? This processreleases huge amounts of energy. Each second, the Sun produces 400,000,000,000,000,000,000,000,000 watts of energy! A star is ‘powered’ by nuclear fusion reactions taking place in its core. Nuclear fusioninvolves light atomic nuclei joining together (fusing) to form heavier ones. 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.
How are elements made? 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. 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 star explodes at the end of its life.
What is a white dwarf? A white dwarf is formed at the end of the life cycle of a star that is about the same size as the Sun. This photograph was taken with the Hubble Space Telescope and shows ancient white dwarf stars in the Milky Way galaxy. The white dwarf stars are shown ringed in blue.
How are black holes formed? 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. If light cannot escape from a black hole, then how can a black hole be observed?
Questions about stars 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
How big is the Universe? When thinking about the Universe, it can be difficult to understand the size and scale that is involved. One way to think about this is to imagine the known Universe scaled down to the size of planet Earth. Our galaxy would be equivalent to the size of just one micron – that’s roughly the same size as a small piece of dust! To find the Sun, you would have to shrink down to stand on the piece of dust. It would then be like finding one particular grain of sand in a seven-metre-wide circular pool filled with sand! And this is just the known Universe…
What is red shift? Scientists examining the light emitted by stars observe dark lines in the spectrum. These dark lines are caused by different elements, such helium, in the stars being studied. Edwin Hubble observed that the pattern of dark lines in light from distant galaxies is shifted towards the red endof the spectrum. This red shift suggests that distant galaxies are moving away from Earth and supports the idea of an expanding Universe. Red shift occurs because of the Doppler effect, which can be observed in sound waves and electromagnetic waves.
This means that very distant galaxies must be moving faster than near, all of which is evidence for the Big Bang theory. How does the Doppler effect work in space? The Doppler effect means that sound moving away from an observer appears to be lower in frequency. The same thing happens with light from distant galaxies, which appears to be shifted towards the low frequency, red end of the spectrum. This means the distant galaxies must be moving away from the Earth. It has also been observed that the further away a galaxy is, the greater the amount of red shift.
This radiation has cooled as the Universe has expanded and is now slightly less than 3 degrees above absolute zero. What is the Big Bang theory? The observation of red shift is a key piece of evidence for the Big Bang theory about the origin of the Universe. This states that the Universe ‘began’ withacolossalexplosion 13,700 million years ago and has been expanding ever since. The other key piece of evidence for the Big Bang theory is cosmic microwave background radiation (CMB). CMB is radiation remaining from the Big Bang explosion and fills the whole of the Universe.
Glossary (1/2) • black hole –An object whose gravitational pull is so strong that nothing can escape, not even light.It is formed after a really massive star collapses in a supernova. • comet –A lump of rock and ice, which has a very elliptical orbit around the Sun. • Doppler effect – The shift in frequency of a sound wave or an electromagnetic wave due to the relative movement of the source or observer. • galaxy –A vast collection of millions of stars. • nebula –A massive cloud of gas and dust in which a star is formed. • neutron star –The very dense core that remains after a massive red giant collapses in a supernova.
Glossary (2/2) • nuclear fusion –The process in which lighter atomic nuclei join together to make heavier atomic nuclei and a massive amount of energy is released. • red giant –The huge red star formed when a star expands and shines less brightly as it starts to die. • red shift –A shift in the wavelength of light towards the red end of the spectrum. It occurs when the light source is moving away from the observer and is evidence for an expanding Universe. • supernova –The huge explosion that occurs when a massive red giant is at the end of its life. • white dwarf –The core that remains after the outer layers of a small red giant drift away.
