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TanglewoodAstronomy Club SUMMER SOLSTICE June 21, 2011

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Page 1: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Tanglewood Astronomy Club

SUMMER SOLSTICE

June 21, 2011

Page 2: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Solstices and the Sun

• From the latin word solstitium, meaning

sun stands still.

• During the summer and winter solstices the

path of the sun above us does not change

much day to day.

Page 3: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

The Solstices – Earth and our Sun

sunrise sunset hours

SUMMER SOLSTICE June 21 5:31 8:47 ~15

Fall Equinox Sept 23 6:55 7:03 ~12

WINTER SOLSTICE Dec 22 7:33 4:39 ~ 9

Spring Equinox Mar 20 7:10 7:20 ~12

• Summer Solstice – in Anchorage Alaska there is

functional daylight all 24 hours.

Page 4: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Gosek (Germany) Sun circle

Concentric ditches and

(reconstructed) wooden fence

with openings that mark the

sunrise and sunset on the

Winter Solstice

Pottery at site indicates circle may

have been built as far back as

7000 years ago. Wikipedia

indicates that this site is the

earliest known solar observatory.

Page 5: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Stonehenge• On summer

solstice sun rises beside the heel stone and would have hit the alter stone.

• Version seen today built ~ 3500 years ago

AP photo

Lefteris

Pitarakkis

Page 6: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Chaco Canyon (Pueblo) Sun Dagger

Unfortunately visitors traffic at the site led

to increased water erosion and the stone

monoliths slipped out of alignment in

1989.

Besides tracking the sun cycle it

appears it also tracked an 18.5 year

lunar cycle.

Built over 700 years ago.

Page 7: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Modern Sun Wheel – UMASS Amherst

Page 8: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Earth’s Orbit about the Sun

~ 91 million miles ~ 95 million milesWinter

Solstice

Dec 22

Summer

Solstice

today

• Earth orbits the Sun in an ellipse

• Earth is actually closer to the Sun during our winter

• But, since the orbit is very close to a circle, not much difference

• About 7% difference in sunlight density from summer to winter

Page 9: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Earth is tilted as it orbits the Sun

• Earth is tilted ~ 24 degrees see globe

• This tilt is the MAIN cause of the summer and winter seasons

• During our summer, the sun is roughly over Palm Beach, Florida

• During our winter, the sun is roughly over Rio de Janeiro, Brazil

• The density of the sunlight is spread over a much larger area around us during the winter, lowering the amount of sun power.

Page 10: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

Solstices and sunlight

• Neglecting absorption of sunlight in air, a

piece of notebook paper in Elmira gets:

• 27 Watts of sunlight on the summer solstice

• Only 9 watts of sunlight at the winter solstice

So we get only 1/3 of the sunlight on Dec 21

compared to June 21.

Page 11: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

What is above us right now ? (If the sun disappeared)

SUN

ORION

Winter

Constellation

Saturn

Jupiter

Mars

Venus

Mercury

Page 12: SUMMER SOLSTICE June 21, 2011 - Tanglewood …tanglewoodnaturecenter.com/Resources/Documents/Tanglewood...SUMMER SOLSTICE June 21, 2011 Solstices and the Sun • From the latinword

FACING SOUTH TONIGHT, ~ 10:30PM

Antares is a Red

SuperGiant Star,

about 15th

brightest in the

sky to eye