Download Grade 9 Science – Unit 4

Grade 9 Applied Science – Space
The Sun
The most important star for Earth is the Sun. Why?
 The Sun provides heat and light energy for all living things
 The Sun’s gravitational pull keeps Earth in a steady orbit (i.e., the right distance to support life).
How is heat and light energy produced?
 NUCLEAR FUSION – under extremely high pressure and temperature, two HYDROGEN NUCLEI
combine to form a helium nucleus. The process produces energy.
How long will the Sun last?
 The Sun has been producing energy for about five billion years. It has only burned 25% of its hydrogen.
After that, the Sun will burn Helium.
 The Sun will continue to produce energy…using hydrogen…for another five billion years.
Parts of the Sun
 CORE – Where nuclear fusion occurs. The
temperature is about 15 000 000OC.
 RADIATIVE ZONE – Area of moving gases where
temperature and pressure increases
 CHROMOSPHERE – The inner atmosphere of the
Sun
 PHOTOSPHERE – The “surface’ of the Sun. It is
NOT solid; rather, it is an area of churning gases.
Average temperature is 5 500OC
 CORONA – The hot outer part of the Sun where
temperatures reach 1 000 000OC.
Other Features
 SOLAR FLARES – Gases moving very quickly from
the chromosphere through the corona. Although they
only last for a few minutes, Solar Flares give off
charged particles that can travel slowly through space towards Earth. The particles interfere with the
Earth’s magnetic field. The resulting electrical effect produces the Northern Lights (Aurora Borealis) and
disrupts radio communications
 SOLAR PROMINENCE – Large sheets of glowing gases bursting outward from the chromosphere. They
can last for weeks and grow to be 400 000 kilometers high.
 SUNSPOTS – Dark, cooler regions of the photosphere that produce violent magnetic storms. These storms
can disrupt radio communications on Earth.
Earth and the Sun
 The Earth orbits the Sun in a counter-clockwise motion. One complete orbit lasts 365.26 Earth days.
 The average distance from the Earth to the Sun is 149 597 890 km. This distance is called the Astronomical
Unit (AU).
 The Sun is 109X larger than the Earth
 The Sun is the largest object in our Solar System. The Sun contains about 98% of the total solar mass in
our Solar System. The mass of the Sun is 332 830X greater than the Earth.