Edexcel IGCSE Physics · Section 8
Astrophysics
The Solar System, stars, galaxies, red-shift, the expanding Universe and the life cycle of stars.
What this section covers
This section covers space physics and the evidence used to understand the Universe.
- Describe the Solar System and wider Universe.
- Explain star life cycles and fusion.
- Use red-shift as evidence for an expanding Universe.
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1
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Orbital Speed: Using the Equation
Spec 8.1
Worked examples using the orbital speed equation.
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2
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The Solar System, Gravity and Orbits
Spec 8.1-8.6
Covers place the solar system within the Milky Way and universe, Explain how mass and distance affect gravitational fields and Compare circular, elliptical and artificial-satellite orbits.
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3
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Stellar Evolution
Spec 8.2
The life cycle of stars, from nebula to their final stages.
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5
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Star Colour, Magnitude and the Hertzsprung-Russell Diagram
Spec 8.7-8.12P
Covers link star colour to surface temperature, Distinguish apparent and absolute magnitude and Interpret the main regions of an H-R diagram.
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6
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Big Bang Evidence, the CMB and Redshift Calculations (Paper 2)
Spec 8.13P-8.16P
Covers describe expansion and cooling of the universe, Explain the cosmic microwave background and Use delta lambda / lambda = v/c.
Frequently asked questions
What keeps planets in orbit?
The gravitational force between the planet and the Sun provides the centripetal force that keeps it in orbit.
What is the life cycle of a star?
A star forms from a nebula, spends most of its life as a main-sequence star, then becomes a red giant or supergiant and ends as a white dwarf, neutron star or black hole.
What is redshift?
Light from distant galaxies is shifted towards the red end of the spectrum, showing they are moving away — evidence that the Universe is expanding.
What is the evidence for the Big Bang?
The redshift of distant galaxies and the cosmic microwave background radiation both support the Big Bang theory.
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