Download day 1 hand out - the sun

The Sun - Our Star
The most important star for Earth is the one at the centre of our solar
system: the sun.
It provides the energy needed by plants and animals, and its
gravitational pull keeps the Earth in a steady orbit.
By studying the Sun, we also learn about other stars.
Since the sun is so close to Earth, it is the brightest object in the sky.
It is so bright, that you cannot see any other stars while the sun is
visible.
The Sun and other stars produce huge amounts of heat and light energy
through a process called nuclear fusion.
Under extremely high pressures and temperatures, two hydrogen
nuclei combine to form a helium nucleus.
Our sun is mostly composed of hydrogen and helium.
Every second, the Sun makes more energy that people have used
throughout history.
Scientists have calculated that the Sun has been producing energy for
about 5 billion years and has only used up 25% of its available
hydrogen.
They also estimate that the Sun will continue to product energy for at
least another 5 billion years before it runs out of hydrogen.
The sun is about 330 000 times larger than Earth
Structure of the Sun
Core
• area with extremely high pressures
• nuclear fusion takes place here
• temperatures up to 15 000 000°C
Photosphere
• The “surface” of the sun
• Made up of churning gases (not solid)
• “cool” region at only 6000°C
• source of visible light for us on Earth
Chromosphere
• inner atmosphere
• just above the photosphere
Corona
• very hot, unstable and changing outer solar “atmosphere” at
about 1 000 000°C
• extends millions of km above chromosphere
• visible during total solar eclipse
Eclipse is very dangerous to look at because
(a) not as bright, so we don't automatically look away, and
(b) there is still plenty of radiation from corona → damage and
possible blindness in just a few seconds!
Features of the Sun
Sunspots
• darker, cooler regions of the photosphere
• can last from hours to weeks
Solar Flares
• as sunspots age, nearby areas may violently erupt
• they travel outward from the chromosphere through the corona
• The sun releases huge amounts of energy outwards into the solar
system, known as → solar wind
• Earth’s magnetic field and components of our outer atmosphere
help protect against the damaging effects of the energy and ions
carried by the solar winds
• Approximately every 11 years, scientists observe problems that
occur with our radio and communication systems, and our
electrical grids and distribution systems.
• These problems have been linked with the occurrence of violent
magnetic storms on the Sun’s surface.
• These storms appear to occur when there are many sunspots
present on the photosphere.
If the ion streams are focused by the magnetic field and carried through
Earth’s atmosphere, streams of colour are created known as Aurorae
Borealis or the “Northern Lights”
Solar prominences
• Large sheets of glowing gases bursting outward from the
chromospheres
• can flow straight out, or loop back into Sun
• they can last for days or weeks and can grow as large as 400 000
km high
Reading and Homework
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Read/Scan pgs 298-304 for a brief overview of the Space Unit
Read pgs 305-307
Complete pg 308 #1-9
Read pgs 309-312
Complete pg 312 #1-5 and #7-9