The Sun Photo from

The Sun Is a star Made of gases Is our primary source of energy 70% hydrogen and 28% helium Light (radiation) Image at

How Big is the Sun? About 110 times wider than Earth Or 1.3 million times bigger than Earth Photo from

How does our Sun compare to other Stars? Active stars range in size from supergiants to dwarfs Stars range from very bright (supergiants) to very dim (dwarfs) Stars range from very hot blue on the outside (O class) to cool red on the outside (M class) Our Sun is in-between--yellow Our Sun is a dwarf—medium mass Our Sun is a medium-bright dwarf

Rotation At the equator, the Sun rotates once every 25.4 days Near its poles, the Sun rotates once every 36 days Known as “differential rotation”

Energy from the Sun Nuclear chain reaction (hydrogen forming helium) Releases radiation (gamma rays) The gamma ray loses energy as it bounces around inside the Sun It is finally released at the photosphere, primarily as visible light Image at

Inside the Sun Core Radiative Zone Convection zone Image at

The Sun’s Atmosphere Photosphere Chromosphere Corona Photosphere image: Chromosphere image: Corona image:

The Photosphere Photosphere: The ‘Surface’ of the Sun, and the layer from which light is given off Sunspots: areas of the sun that look dark due to being cooler

Chromosphere & Corona Chromosphere: middle layer of the Sun’s atmosphere Corona: Largest layer of the Sun’s atmosphere

Solar Wind Blows charged particles and magnetic fields away from the Sun Charged particles captured by Earth’s magnetic field Create Auroras or Northern and Southern Lights Image at

Coronal Mass Ejection CMEs: large amount of electrically-charged gas are ejected suddenly from the Sun’s corona CMEs can damage satellites and interfere with radio and power distribution equipment

Prominences and Flares Prominences- huge arching columns of gas Flares: when gases near a sunspot brighten shooting outward

Radiation Our Sun (and all active stars) emits radiation –Radio, infrared, visible, ultraviolet, x-ray and even some gamma rays –Most of the sunlight is yellow-green visible light or close to it The Sun at X-ray wavelengths Image and info at and

Sun as a Source of Energy Light from the Sun is absorbed by the Earth, unevenly to: –drive wind bands – which drive surface currents –drive deep ocean currents –drive water cycle –drive weather NASA image at Credit: NASA GSFC Water and Energy Cycle

Our Sun is a Regular/ Small Star Image at

Stars begin as a cloud of gas and dust called nebula Image at

Main Sequence Image at Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence starprotostarsmain-sequence

After billions of years a Main sequence star will turn into a Red Giant

By 5 billion years… White Dwarf: This happens when all that is left is the hot dense core Image at

Image at Supergiant's and Supernovas Supergiant's: Extremely large (and unstable red giants Supernovas: The explosion that occurs when the supergiant’s core collapses

Black Hole If the remaining dense core from a supernova collapses to a point The gravity from this point is so strong that nothing can escape from it not even light. –If you were to shine a light into a black hole the light would simply disappear

Life of a Star