Topic 16 – Cosmology — Edexcel GCSE Astronomy
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Topic 16 – Cosmology explained
The Big Bang model is supported by several independent observations.
Read the full explanation
Quasars (QSOs) are extremely luminous active galactic nuclei seen at great distances; their large redshifts show they are receding, and their existence predominantly in the early Universe supports an evolving cosmos. The cosmic microwave background (CMB) is faint microwave radiation at about 2.7 K coming from all directions; it is relic radiation from the hot early Universe. The Hubble Deep Field image, a long exposure of a tiny sky region, revealed thousands of distant galaxies at various stages of evolution, showing that the Universe changes over time. These lines of evidence indicate an expanding, evolving Universe that began in a hot, dense state.
Your focus
- Describe quasars (QSOs) and explain how their properties support the Big Bang theory.
- State the nature and temperature of the cosmic microwave background and explain its significance.
- Explain how the Hubble Deep Field image provides evidence for an evolving Universe.
Topic 16 – Cosmology exam tips
Marking Points
- Quasars (QSOs) are very distant, extremely luminous active galaxies; their high redshifts indicate they are receding and existed predominantly in the early Universe.
- The CMB is microwave radiation at approximately 2.7 K coming from all directions; it is interpreted as relic radiation from the hot early Universe.
- The Hubble Deep Field image shows thousands of distant galaxies at different stages of evolution, providing evidence that the Universe evolves.
- The combination of these observations supports the Big Bang theory: an expanding Universe that was once hot and dense.
Examiner Tips
- 💡Link each observation to a specific feature of the Big Bang model: expansion, relic radiation, or evolution.
- 💡Quote the CMB temperature as about 2.7 K and state that it is microwave radiation.
- 💡For the Hubble Deep Field, mention that it shows many distant galaxies at different stages, supporting an evolving Universe.
Common Mistakes
- Thinking the CMB comes from stars or galaxies: it is relic radiation from the early Universe, not starlight.
- Believing quasars are nearby objects or existed only in the early Universe: they are extremely distant and mostly seen in the early Universe, but not exclusively.
- Assuming the Hubble Deep Field shows only nearby galaxies: it reveals thousands of very distant galaxies at different evolutionary stages.