Grade 8 Natural Sciences (NS) Summaries - Term 4 (Via Afrika): These summaries are compiled using the Via Afrika textbook's Term 4 content. The summaries are in English, with additional notes provided by the compiler.
Strand 4 - Planet Earth and beyond
Topic 1: The Solar System
Topic 2: ...
, Light years, light hours • A system of stars held together by gravity. The Milky Way Galaxy
• Comprises the Sun and over 100 billion other stars.
and light minutes • The Milky Way band encircles the entire sky, resembling luminous clouds.
• Milky Way's hazy light path was caused by milk spilt during Hercules' feeding by Juno.
• Distances to stars and other objects
• Galaxy's shape formed by the positions of billions of stars.
beyond the Solar System are too large
• Spiral shape with curved arms from another galaxy.
to be measured in kilometres.
• Sun and Earth in one of the spiral arms.
• Measurements are expressed in terms
• Brightness varies depending on viewing direction.
of light travels in a year, a day, or an
• Galaxy rotates around its centre, with stars near the centre moving the fastest.
hour.
• Light travels 300,000 km in one
second, approximately seven and a Our nearest star
half times around Earth.
• Light Years: • Alpha Centauri - Brightest star in Centaurus, 270
Sample
o A light year is the distance light
travels in a year, approximately 10
trillion kilometres.
o Alpha and Beta Centauri are
approximately 4.2 light years away,
T2: Beyond
the Solar
System
thousand times further from Earth than Sun.
• Brighter of two Southern Cross pointers.
• Second light bulb 80 km away from first.
• Despite proximity, distant from Solar System.
42 trillion kilometres away, and 300
Summaries after sample
The long wait for signals
light years away respectively.
• Light Hours: from Alpha Centauri
o Light travels in an hour, with Sun-
Neptune distance being 4 light hours. • Radio signals travel at
o Sun's light travels 6 hours beyond Beyond the Milky Way Galaxy light speed, a million
Pluto to the Kuiper belt. times faster than
o The Solar System's diameter is • Beyond the Milky Way Galaxy: sound.
approximately 13 light hours. o One of billions of galaxies with ideal conditions for observing 2000-2,500 stars. • Alpha Centauri's
• Light Minutes: o One of billions of other galaxies with a vast number of stars. signals took 4.2 years
o Sun's light travels 8 minutes to Earth. • Size of the Observable Universe: to reach Earth.
• Looking Back in Time: o Big Bang Theory suggests the Universe was once hot, tightly packed matter • Beta Centauri's
o The Sun's sudden 'switching off' could expanding rapidly. signals took 300
be detected in 8 minutes. o The Universe's age is approximately 14 billion years, making it difficult to see years.
o Southern Cross pointers show Alpha galaxies further than 14 billion light years away.
Centauri and Beta Centauri as they • Shapes and Sizes of Galaxies:
were 4.2 and 300 years ago. o Three neighbouring galaxies visible from Earth: Great and Small Magellanic Clouds,
and Andromeda Galaxy.
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