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Year 11
AQA
Foundation

Observing the universe

I can describe what redshift is and how it is measured.

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New
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Year 11
AQA
Foundation

Observing the universe

I can describe what redshift is and how it is measured.

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Lesson details

Key learning points

  1. Telescopes extended what was visible after their invention in the seventeenth century.
  2. Images detected by telescopes in space are not distorted by effects of the Earth’s atmosphere.
  3. A galaxy is a group of hundreds of billions of stars, and there are many galaxies spread across the universe.
  4. A visible spectrum of light emitted from stars or galaxies shows dark lines of frequencies of light.
  5. Red shift is the movement of hydrogen lines towards the red end of the visible spectrum.

Keywords

  • Space telescope - is a telescope positioned in space to avoid atmospheric interference and observe parts of the spectrum which cannot reach the Earth’s surface

  • Galaxy - is a collection of many millions or billions of stars held together by gravitational forces

  • Redshift - is the increase in the wavelength of light (and decrease in its frequency) cause by the movement of a star or galaxy away from us

Common misconception

Stars twinkle (change brightness rapidly).

Explore the ideas that Earth’s atmosphere is made of moving air that refracts light from stars in changing directions to distort the light coming from stars.


To help you plan your year 11 physics lesson on: Observing the universe, download all teaching resources for free and adapt to suit your pupils' needs...

This lesson goes beyond the syllabus in places in order to provide pupils with an understanding of redshift, which is necessary for understanding the big bang theory for the origin of the universe.
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This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
A star fuses hydrogen in its core. It is stable for long periods of time (often billions of years).
Correct Answer: main sequence
Q2.
What type of star will the Sun change into next, after it stops fusing hydrogen in its core (in about 5 000 000 000 years)?
red dwarf star
white dwarf star
Correct answer: red giant star
white dwarf star
Q3.
Sort the following stages of a star's life, for a star similar in size to the Sun, into the order in which they take place.
1 - nebula
2 - protostar
3 - main sequence star
4 - red giant star
5 - white dwarf star
6 - black dwarf star
Q4.
What is a giant exploding star called?
Correct Answer: supernova, a supernova, super nova, a super nova
Q5.
What is a neutron star that is formed from the core of a supernova?
a very large and hot white dwarf star
an incredibly hot ball of plasma and gas
an incredibly dense ball of atoms
Correct answer: an incredibly dense ball of neutrons
Q6.
What is a black hole that is formed from the core of a particularly large supernova?
the core of a massive star compressed to a few thousand metres across
the core of a massive star compressed to a few hundred metres across
the core of a massive star compressed to a few metres across
Correct answer: the core of a massive star compressed to almost no size at all

Exit quiz

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6 Questions

Q1.
Which of the following optical instruments can improve what we can see in space?
Correct answer: binoculars
microscopes
stethoscopes
Correct answer: telescopes
Q2.
What makes a star appear to twinkle in the night sky?
clouds
Correct answer: moving air
gases around the star
nebulae in space
Q3.
What are the advantages of using a space telescope compared to a telescope on Earth?
It is very expensive to construct and launch.
Correct answer: It encounters no atmospheric distortion.
Correct answer: It can detect more types of radiation.
It is smaller in size.
Q4.
How do Messier objects that can be seen with a telescope differ in appearance from stars?
They are much brighter.
They have distinct colours.
Correct answer: They don't have sharp outlines.
Their brightness varies in a regular pattern.
Q5.
What are absorption lines in a spectrum of light from a star?
coloured lines that add together to make a visible spectrum
black lines on a visible spectrum caused by a telescope
Correct answer: black lines on a visible spectrum caused by gases around a star
black lines on a visible spectrum caused by air in Earth's atmosphere
Q6.
What observation shows that redshift has occurred and that the wavelength of light from a distance galaxy has increased?
there is less red light in the visible spectrum of the galaxy
there is more red light in the visible spectrum of the galaxy
Correct answer: absorption lines in its spectrum have lower than expected frequencies
absorption lines in its spectrum have higher than expected frequencies