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12.5Earth and Space 03. Space

Stars nebulae galaxies and the Universe — Cambridge Checkpoint Science 0893 Revision Notes & Topical Questions

5 min read 9 parts Lesson 5 of 6 1 quiz

📚 Cambridge Checkpoint Science 0893 Hub / Topical Revision
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Lesson summary

12.5 Stars, nebulae, galaxies and the Universe — CHECKPOINT - Lower Secondary Science 0893 notes: Describe stars, nebulae, galaxies and the scale of the Universe.Star — a huge ball of hot gas that gives out light and heat.The Sun is a star.Star energy — stars are powered by nucle…

  • Light year
  • Looking back in time
  • Nuclear fusion
  • Nebula — a huge cloud of dust and gas in space.Stars form in nebulae, such as the Orion Nebula
  • Galaxy — a huge group of billions of stars, gas and dust held together by gravity
  • Milky Way — the spiral galaxy that contains our Solar System.It contains about 100 to 400 billion stars

Section 1 of 9Stars

Star
  • Star a huge ball of hot gas that gives out light and heat.
  • The Sun is a star.
Star energy
  • Star energy stars are powered by nuclear fusion, in which hydrogen nuclei join to release energy.

Section 2 of 9Nebulae

Nebula
  • Nebula a huge cloud of dust and gas in space.
  • Stars form in nebulae, such as the Orion Nebula.
Gravity
  • Gravity pulls the dust and gas together into a growing ball, which becomes a star if it gets big and hot enough.
  • Young stars can be seen inside nebulae.

Section 3 of 9Galaxies

Galaxy
  • Galaxy a huge group of billions of stars, gas and dust held together by gravity.
Milky Way
  • Milky Way the spiral galaxy that contains our Solar System.
  • It contains about 100 to 400 billion stars.
Andromeda
  • Andromeda the nearest large galaxy to the Milky Way.

Section 4 of 9Types of galaxy

TypeShapeStarsGas and dust
SpiralFlat disc with spiral armsYoung and oldPlenty, with star formation in the arms
Barred spiralSpiral with a central barYoung and oldPlenty
EllipticalOval or roundMostly oldLittle
IrregularNo clear shapeMixedPlenty

Section 5 of 9Scale

1Light year
  • Light year the distance that light travels in one year, about 9.5 trillion km.
  • It is a unit of distance, not of time.
2Distances
  • Distances the Milky Way is about 100 000 light years across and Andromeda is about 2.5 million light years away.

Section 6 of 9Order of size

  1. Earth
  2. Solar System
  3. Milky Way galaxy
  4. Local group of galaxies
  5. The Universe

Section 7 of 9Universe

Universe
  • Universe everything that exists, including billions of galaxies.
Looking back in time
  • Looking back in time light from distant galaxies takes millions of years to reach us.
  • We see them as they were in the past.

Section 8 of 9Key terms

TermMeaning
StarA ball of hot gas that gives out light.
NebulaA cloud of dust and gas in space.
GalaxyA huge group of stars, gas and dust held by gravity.
Milky WayThe galaxy that contains our Solar System.
Light yearThe distance light travels in one year.
UniverseEverything that exists.
Nuclear fusionJoining of hydrogen nuclei, releasing energy.
GravityThe force that holds galaxies together.

Section 9 of 9Exam technique

1
Thinking a light year is a unit of time — it is a unit of distance.
2
Mixing up the Solar System and the galaxy — the Solar System is a tiny part of the Milky Way.
3
Thinking all stars are in the Solar System — the Sun is the only star in the Solar System.
4
Thinking a nebula is a star — a nebula is a cloud of gas and dust from which stars form.

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