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, thermal energy 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).
Our Sun is at the centre of our Solar System.
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 5 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 5 billion years.
The Sun is composed of gas and consists of many layers. How do these layers of gas stay together?
Layers of the Sun
 CORE – Where nuclear reactions
(i.e., fusion) occurs. These reactions
use and produces a lot of energy. As
a result, the core’s temperature is
about 15,000,000OK.
 RADIATIVE ZONE – Area of moving
gases where temperature and
pressure increases. The core
releases it energy outward through
this layer.
 CONVECTIVE ZONE – Gas at the
surface of this layer begins to “cool.”
As it cools, it gets heavier and sinks
back towards the core. Hot gas
continues to rise. This creates a
convection current of moving gases
(see diagram)
 CHROMOSPHERE – The inner
atmosphere of the Sun.
Temperatures in this layer are about 10,000OK
 PHOTOSPHERE – The “surface’ of the Sun. It is NOT solid; rather, it is an area of churning
gases. Average temperature is 5,500OK
 CORONA – The hot outer part of the Sun where temperatures reach 2,000,000OK.
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 or REVOLVES around the Sun in an oval-shaped (elliptical) path in a counterclockwise motion. One complete revolution 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.
 It takes sunlight and 8 MINUTES to reach the Earth from the Sun. How many LIGHT YEARS is 8
minutes? NOTE: It is a very, very small number.
How are the NORTHERN LIGHTS formed?
 Sun constantly releases electrically-charges particles into space. These particles move at a rate
of about 400 km/s. The particles travel on SOLAR WINDS
 Earth is surrounded by a MAGENTIC FIELD. The field is closest to the Earth at the North and
South Poles. The field also contains gases.
 Solar winds meet the Earth’s magnetic field, move along the magnetic field’s lines and react with
the gases
 The reactions produce lights. If the solar winds strike oxygen (O2), the light is green. If they
strike nitrogen (N2), the colour is red.
 These colours are the AURORA.
TASK – Make a diagram illustrating your understanding of the formation of the Northern Lights