8.2 The Sun
pg. 309
Key Concepts:
1. Careful observation of the night sky can offer clues about the motion
of celestial objects.
2. Celestial objects in the Solar System have unique properties.
3. Some celestial objects can be seen with the unaided eye and can be
identified by their motion.
4. The Sun emits light and other forms of radiant energy that are
necessary for life to exist on Earth.
5. Satellites have useful applications for technologies on Earth.
6. The study of the night sky has influenced the culture and lifestyles of
many civilizations.
Electromagnetic (EM) Radiation: is the energy emitted from matter,
consisting of electromagnetic waves that travel at the speed of light.
Electromagnetic (EM) Spectrum: the range of wavelengths of
electromagnetic radiation, extending from radio waves to gamma rays, and
including visible light.
- Stars emit electromagnetic radiation, which travels at the speed of light.
- The Electromagnetic Spectrum consists of radio waves, microwaves,
infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.
- The greater the wavelength the less energy, the smaller the wavelength the
greater the energy, inversely proportionate.
- The Sun’s electromagnetic radiation supports life on our planet, and drives
our weather and climate.
The Structure of the Sun
- The Sun is composed of many layers of gas.
- The centre of the Sun is called the core. The Core has extreme
temperatures
(15 000 000 oC) and great pressure.
- Particles are moving at great speeds and collide. The particles fuse together
as they collide.
- During nuclear fusion, large amounts of energy are released.
- The layer of gases surrounding the core is called the Radiative Zone. It
takes a million years for energy to ravel through this zone.
- Energy from the radiative zone travels to the Connective Zone.
- Energy moves from the connective zone to the Photosphere. Here light and
other forms of energy can escape into space.
- The temperature in the photosphere is 5500 oC.
- The Sun’s Atmosphere is divided into two sections, the Chromosphere and
the Corona.
Figure 2: The Structure of the Sun
The Sun’s Surface
Sunspots: dark spots appearing on the Sun’s surface that are cooler than the
area surrounding them.
Solar Flare: gases and charged particles expelled above an active sunspot.
Solar Prominence: low-energy gas eruptions from the Sun’s surface that
extend thousands of kilometers into space.
- The Sun rotates on its axis. A complete rotation occurs every 25 days.
- Photosphere has texture and appears as boiling liquid.
- Sunspots are dark cool areas on the Sun’s photosphere.
- They are caused by disturbances in the Sun’s magnetic field.
- Solar flares are active regions near the Sunspots.
- Solar flares release large quantities of gas and charged particles.
- Solar flares are caused by rapid changes in the magnetic fields.
- Solar prominences are slow ejections of gas.
The Sun’s Effect on Earth
- The activity on the outer surface of the Sun causes solar storms.
- Solar winds are strongest during solar flares and prominences.
The Auroras
Aurora Borealis: a display of shifting colours in the northern sky caused by
solar particles colliding with matter in Earth’s upper atmosphere.
- Surrounding the Earth are atoms of different types of gases. (O2, Ar, N2,
CO2)
- As the solar winds enter the Earth’s atmosphere, specifically at the North
and South Poles, the Earth’s magnetic fields influence the solar particles as
they interact with atmospheric gases to generate light arrays.
- These light arrays are called Auroras Borealis in the Northern Hemisphere,
and Auroras Australis in the southern Hemisphere.
Communication Disruptions
- Solar activity can negatively impact artificial and man made satellites.
Radiation Hazards
- Radiation from solar storms can be very hazardous to humans and their
technology.
- The Earth’s atmosphere protects us.
Check Your Learning
Questions 1 – 9, page 312
Summary:
- The Sun emits radiation across most of the EM spectrum. Some of the
Sun’s energy is absorbed by Earth’s atmosphere and some is reflected into
space. Almost all of the enrgy that reaches Earth’s surface comes from the
Sun.
- The Sun is necessary for life on Earth.
- The Sun has various layers with different temperature and properties.
- The Sun constantly undergoes changes due to storms and turbulent
atmosphere that also affects Earth.
- The aurora borealis (northern lights) and aurora australis (southern lights)
are caused by the interaction between solar particles and the Earth’s
atmosphere near the North and South Poles.
- Solar radiation cause communication disruptions and can be hazardous to
human health.