Sun and Seasons

Page
1

Slide 1

Sun and Seasons

Welcome!

Created by the Lunar and Planetary Institute

For Educational Use Only

LPI is not responsible for the ways in which this powerpoint may be used or altered.

Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html

Slide 2

What are we going to cover

Properties of the Sun

Influence on Earth:

Gravity

Light

Solar wind

Life cycle of the Sun

Seasons

Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html

Slide 3

The Sun

Is a star

Made of gases

Is our primary source of energy

70% hydrogen and 28% helium

Light (radiation)

Image at http://science.nasa.gov/headlines/y2007/images/chromosphere/LimbFlareJan12_strip2.jpg

Slide 4

How Big is the Sun?

Activity: Let’s measure the Sun

Slide 5

How Big is the Sun?

About 110 times wider than Earth

Or

1.3 million times bigger than Earth

Photo from http://sohowww.nascom.nasa.gov/bestofsoho/bestofsoho.html

Slide 6

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

Slide 7

So is our Sun an average star?

No—most stars are smaller and cooler than our Sun BUT

Most of the bright stars we see are bigger and hotter

Slide 8

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”

High cadence solar rotation, EIT 195Š(Dec. 10-24, 1999) Movie at http://sohowww.nascom.nasa.gov/bestofsoho/Movies/EITdec99/EITdec99sm.mpg

Slide 9

Sun’s Magnetic Field

Winds up due to differential rotation

Eventually forms loops and becomes tangled

Animation of how the Sun's magnetic field winds up and loops out.