Our Solar Centre The Sun An Example of a Solar Tornado  Has solar tornadoes  A tall funnel of twisting plasma mmm!  Can be 20,000km (diameter) and spins at 500,000km/h  Has a temperature of several million degrees Celsius

The Sun – a Typical Star  Composed mainly of:  Hydrogen  Helium  Also has heavier elements:  Iron  Carbon  Oxygen  Was born about 5 billion years ago, and will live for about 5 billion more years

The Nature of the Sun  Emits radiation in almost all forms found in the electromagnetic spectrum  Visible light, UV radiation (causes sunburn)  Its mass is estimated by observing how fast the planets, etc. orbit around it  Nuclear reactions in the Sun are the same ones in the most powerful hydrogen bomb  Hydrogen is converted into Helium (releases ENERGY)

Layers of the Sun  6 main layers: 1. Core  Inner part, temps at 15 million degrees Celsius  Where nuclear fusion happens 2. Radiative Zone  Outside the core, dense plasma  Light takes 100,000 years to pass through it (meaning...?) 3. Convective Zone  Big bubbles of hot plasma ooze up to surface, w/energy  Cool plasma come down from surface to heat up again  Constant circulation of plasma is called convection 4. Photosphere  Boundary between inside and outside of Sun, making it yellow  What we see on Earth  has the lowest temperature of 5500 degrees C 5. Chromosphere  Reddish, but can’t see it unless there’s a solar eclipse b/c of photosphere 6. Corona  Outermost layer, extends for millions of km; most visible during solar eclipse

Label Our Sun!!

Surface Features of the Sun  The Sun has a magnetic field  Generated by movement of plasma deep in Sun  It extends far out into space  Very powerful

Surface Features of the Sun  Sunspots  A region on surface of the Sun that’s cooler than surrounding areas  Where magnetic field is extremely strong  This slows down convection  no mixing of plasma  Cools from 600o ºC  4000 ºC  Every 11 yrs, max # sunspots reached

 Prominences  A large, usually curved, bright stream of particles  Extends out from photosphere into corona  May last for many hours

 Solar Flares  Massive explosion at surface of Sun  Interacts with chromosphere and corona  Flings hot plasma into space

 Coronal Mass Ejection  Extremely powerful kind of flare  Large amount of plasma is thrown out at 1000km/s  Earth’s magnetic field protects us when this meets the Earth  Causes auroras  Can damage orbiting satellites and electrical transmission lines

Learning Checkpoint 1. Which two elements make up more than 99% of the Sun? 2. Where in the Sun does nuclear fusion occur? 3. Name four types of surface features of the Sun. 4. How can a coronal mass ejection on the Sun cause damage on Earth?

Sun’s Effects on Earth 1. Solar Wind  Constant flow of charged particles streaming out of the Sun’s surface in all directions  Helped to create the solar system  Electrical equipment can be damaged by this

2. Aurora Borealis (Northern Lights)  Solar wind creates this display of green, yellow, and red light in the skies  Aurora Australis (Southern Lights)  Happens when charged particles of solar wind collide with atoms in Earth’s atmosphere  Particles are trapped from solar wind in magnetic field and taken towards north and south poles

How the Solar System Formed  After Sun was formed (from what!?!?) the leftover dust, gases, etc. in nebula continued to spin  This created a disk around the new star  Bodies began to form  Created our planets, moons, asteroids, comets  This is how other star-and-planets systems formed too  Planet: a celestial object orbiting one or more stars; can form a spherical shape  DOES NOT create and radiate own light  just reflects light of star(s) it orbits

How the Solar System Formed

Rocky Inner Planets  Formed when spinning dust and gas slammed into each other and started sticking together  Larger particles made more collisions and grew faster  Gravity caused them to contract and bind together  Objects too near the Sun got sucked into it  Four large objects lasted: Mercury, Venus, Earth, Mars

Earth’s Moon  Few hundred million years later...something as big as Mars may have hit the Earth  Objects re-melted and mixed  Metal core melded with Earth’s core  Crusts melded together  Earth cooled  Pieces of debris from collision were caught by Earth’s gravity and eventually compacted into the Moon Mars is the only other rocky planet with moons!!

Asteroid Belt  Between Mars and Jupiter  Small as grains of sand – 1000km across  Scientists look for these near other stars  Could indicate there are rocky planets there too!!  This is where we got the age of the solar system  Asteroids fell to Earth and oldest one was 4.56 billion  Earth was therefore formed at the same time  Sun must have been around while earlier

Gaseous Outer Planets  Jupiter, Saturn, Uranus, Neptune  After asteroid belt, “snow line”  On Sun side of this line, it’s where Sun’s radiation keeps H 2 O in gas phase  In snow line, water’s cooled and forms droplets, then freezes  Ice acted as a glue for gas and dust to stick together  these planets grew faster!!  All gas giants are orbited by many moons  Jupiter and Saturn each have more than 60!!

Minor Planets  After gas giants, many large balls of ice formed  minor or dwarf planets  Pluto: most famous  3 moons: Nix and Hydra (tiny), and Charon (1/2 Pluto)  Millions of objects besides these orbiting the Sun  Some larger, some smaller, than Pluto  Create a thin disk like asteroid belt around entire solar system  25 of them are large enough to be considered minor planets

Comets and Meteors  Oort Cloud: most distant region of SS, consisting of billions of fragments of ice and dust  major source of comets  Comet: celestial object made of ice and dust  Tail is created by sun heating and breaking apart some of the ice particles  Meteoroid: small pieces of rock/metal travelling throughout the solar system (no path)  Meteor: meteoroid that enters Earth’s atmosphere and begins to burn up because of FRICTION  Meteorite: a meteor that does not burn up completely and hits Earth

Earth in Motion  At equator: 12 h daylight, 12 h night  In Arctic: some days, Sun doesn’t set (summer) and some days, Sun doesn’t rise (winter)  What causes this?  Tilt of the Earth on its axis

Two Types of Motion RotationRevolution  One complete spin (counter clockwise) of the Earth on its AXIS  Takes about 24h  Earth moves at 1670 km/h  Axis is tilted at 23.5 º  Creates day and night  One complete orbit of Earth around the SUN  Takes about 1 year  Creates seasons  Tilted axis + revolution  Tilted TO Sun = summer  Tilted AWAY FROM Sun = fall

Rotation and Revolution

The Moon  1/6 Earth’s mass  Also rotates on an axis  Rotation and revolution are about equal  27.3 days, moon rotates and revolves once  This is why we always see the same side of the moon  Reflects Sun’s light  changes in look (phases)  One complete change of phases  lunar cycle  Full moon: Earth between moon and sun  New moon: moon between Earth and sun

Eclipses Solar Eclipse Lunar Eclipse  When moon blocks Sun’s light to Earth  Two types 1. Partial: Sun is partially blocked 2. Total: Sun is completely blocked  When Earth blocks Sun’s light from shining on moon  Two types 1. Partial: moon is partially blocked 2. Total: moon is completely blocked

Tides  The alternate rising and falling of level of oceans everyday  Caused by:  Rotation of the Earth in the presence of the Moon  Rotation of the Earth in the presence of the Sun  Example: Bay of Fundy  Largest difference between high tide and tow tide levels (as much as 17 m in one day!)