The Sun. Sun Considered a medium STAR 93,000,000 miles away from Earth 1.39 million kilometers in diameter (one million Earths can fit inside the sun.

The Sun

Sun

• Considered a medium STAR

• 93,000,000 miles away from Earth

• 1.39 million kilometers in diameter (one million Earths can fit inside the sun

• State of matter - plasma

More on the Sun

• Contains 99% of mass of our solar system

• Made of 82% hydrogen, 17% helium, 1% other

Our Sun compared to other suns!

Our Sun compared to other even larger suns!

The sun’s structure

• Core – 27 million degrees Fahrenheit, where thermonuclear fusion occurs

• Photosphere – innermost part of sun’s atmosphere but still visible to us, made of hydrogen gas that burns at 9000 degrees Fahrenheit – causes it to glow yellow

The sun’s structure

• Chromosphere – inner atmosphere, region of glowing gas; red color caused by ionization of hydrogen

• Corona – outer atmosphere, thin layer of gas that extends millions of km beyond chromosphere

The sun’s corona

Thermonuclear fusion

• The sun is so bright because it goes through thermonuclear fusion – when hydrogen atoms get turned into helium atoms due to high heat and pressure– Releases massive amounts of heat and light

as a byproduct

– This energy and light released from the sun takes 8 minutes to reach us

What is a sunspot?

• An area on the sun that has extremely strong magnetic activity

• The magnetic activity does NOT allow convection so it is a cool region

• Looks like a dark spot• Lasts 2 weeks and only

occurs in 11 year cycles

Magnetic fields

Sunspot activity since 1760

Recent sunspot activity

2013

• We are still in solar maximum. What is happening?

What else should we know about sunspots?

• They can cause solar flares – When hot gases erupt

from the surface of the sun sending ions and radiation into space

Solar flares create solar winds

Solar Flares

Close Up of Flares

Solar prominence

• Streamers of hot gases arching above photosphere

• Do not disrupt Earth’s communications

Solar winds

• Every 11 years, the suns magnetic poles reverse and release energy– Billions of tons of particles fire into space at 1

million mph, at the peak it is called the solar maximum, speeds can reach 3 million mph

– We are in a solar maximum now

Solar Wind – a continuous flow of electrons and protons from the sun into space

How is Earth protected?

• Magnetosphere- magnetic field that is surrounding the Earth

• Without the magnetic field, the solar winds would be much more dangerous

Earth’s Magnetosphere

Solar Flares in the news

Why does this matter?

• Strong solar flares and sunspots can damage our communication systems and electrical systems

• Also increase aurora activity

• Aurora Borealis and Australis – lights caused by interactions of atomic particles between solar wind and the ionosphere

Effect of solar flares and solar winds

• http://www.teachersdomain.org/resource/ess05.sci.ess.eiu.solarwind/

• https://www.youtube.com/watch?v=Hueen7jPi0w

SDO (solar dynamics

observatory)

• AIA images the outer layer of the Sun's atmosphere (corona) at temperatures from 20 thousand to 20 million degrees.

• EVE keeps track of the extreme ultraviolet (EUV) rays that the Sun sends towards us. UV rays cause skin cancer. Extreme UV rays are even more dangerous. Our atmosphere absorbs UV, keeping us safe.

• HMI will measure the ripples and the magnetic fields on the surface of the Sun (photosphere) to determine what is happening on the inside.

Photo taken in extreme ultraviolet on March 30, 2010 by the Solar Dynamics Observatory that was launched by NASA on February 11, 2010.

SDO photograph