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 it’s 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.

Our sun is mostly composed of hydrogen and helium. 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 produce energy for at least another 5 billion years before it runs out of hydrogen. The sun is about 330 000 times larger than Earth

Lets study the Structure of the Sun

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

Structure of the Sun 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 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

Features of the Sun 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.

Solar Flare

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”

Features of the Sun 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

Solar Prominence

Reading and Homework Time □ 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