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Unit 6: Sound and space

Nebulae — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 8 parts Lesson 11 of 14 1 quiz

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Nebulae — HIA INTERNATIONAL notes: Describe nebulae, their composition and how stars form in stellar nurseries.Nebula = a cloud of dust and gas in space; the plural is nebulae.Gases — mostly hydrogen with a smaller quantity of helium.Density — the particles are very far apart; a …

  • Compared with a galaxy
  • From dying stars
  • Northern hemisphere
  • Southern hemisphere
  • Stellar nursery
  • Not all nebulae

Section 1 of 8What a nebula is

Nebula
Nebula a cloud of dust and gas in space; the plural is nebulae.
Gases
  • Gases mostly hydrogen with a smaller quantity of helium.
Density
  • Density the particles are very far apart;
    • a nebula the size of the Earth would have a mass of only a few kilograms.
Size
  • Size most are very large, many more than 10 000 times bigger than the Solar System.
Compared with a galaxy
  • Compared with a galaxy a nebula is a cloud in space and a galaxy is a huge collection of stars.

Section 2 of 8How nebulae form

From dying stars
  • From dying stars some form when giant stars reach the end of their life and explode, sending dust and gas over a wide area.
Recycling
  • Recycling material from dead stars, including carbon, oxygen and iron, is recycled into new nebulae, stars and planets.
Glow
  • Glow hot stars nearby heat the gas or light the dust; dark nebulae block light from stars behind them.

Section 3 of 8Examples

Northern hemisphere
  • Northern hemisphere the Orion nebula is easy to see without a telescope.
Southern hemisphere
  • Southern hemisphere the Tarantula nebula is visible without a telescope.
Hemisphere
Hemisphere half of the Earth, north or south of the equator.
Size
  • Size the Orion nebula is 24 light years across.

Section 4 of 8Stellar nurseries

Stellar nursery
Stellar nursery an area in space where stars are formed.
Not all nebulae
  • Not all nebulae only some types of nebulae act as stellar nurseries.
Young stars
  • Young stars some are only half the mass of the Sun and have not yet reached full brightness.

Section 5 of 8How a star forms

1
Gravity pulls dust and gas together.
2
As the mass collects, the inward pull of gravity increases.
3
The pressure inside the new star becomes very large.
4
The high pressure causes heat.
5
Atoms react with each other (nuclear fusion), so the star gives out heat and light.
How a star forms
Planets
  • Planets leftover material spinning around the star forms a flat disc that clumps into planets, moons, asteroids and comets.
Our Solar System
  • Our Solar System formed in this way about 4.6 billion years ago.

Section 6 of 8Observing nebulae

Telescopes
  • Telescopes the Hubble Space Telescope takes photographs of nebulae from space.
Infrared
  • Infrared telescopes that detect infrared, such as James Webb, can see through dust to stars forming inside nebulae.

Section 7 of 8Key terms

TermMeaning
NebulaA cloud of dust and gas in space.
Stellar nurseryAn area in space where stars are formed.
HemisphereHalf of the Earth, north or south of the equator.
GravityThe force that pulls dust and gas together.
Nuclear fusionAtoms reacting in a star to give out heat and light.
Light yearA unit of distance used in space.

Section 8 of 8Exam technique

1
A nebula is the same as a galaxy — a nebula is a cloud of dust and gas; a galaxy contains many stars.
2
Nebulae are dense — their particles are very far apart.
3
All nebulae make stars — only some act as stellar nurseries.
4
Nebulae are made mainly of oxygen — they are mostly hydrogen and helium.

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