wonders of the sky 2009 sunset sky

Wonders of the Sky

Wonders of theSunset Sky

Water Reflection

Setting Sun

• The setting or rising sun can often appear distorted due to effects of earth’s atmosphere

• The setting or rising sun often appears oval-shaped, and its light is reddened

• The sun can also appear “broken” in separate layers, each created by air of different temperatures

http://www.isc.tamu.edu/~astro/research/sdsun950423.gif

Oval Setting Sun

http://www.astro.uiuc.edu/~kaler/arc/vt1-1b.jpg

Eclipsed Setting Sun, Alaska, March 18, 2007

Green Flashes

• Sometimes the setting sun will emit a green flash, an intense burst of green light

• The green flash is caused by the atmosphere acting as a prism upon the last bit of setting sun

• The green flash is usually only observed as the sun sets over the ocean

http://mintaka.sdsu.edu/GF/papers/JOSA/green.gif

Crepuscular Rays

• Visible near sunrise or sunset

• Crepuscular rays are a perspective effect, the rays are actually parallel

• Also anti-crepuscular, appear to converge opposite the sun

http://www.cimms.ou.edu/~doswell/photopg/crepusc.JPG

Anticrepuscular Rays

http://epod.usra.edu/archive/images/0507200013.jpg

Parallel Rays?

Crepuscular Sunset

Volcanic Sunsets• Major volcanic eruptions

inject tremendous amounts of dust into the atmosphere

• This dust creates dramatically red that last for months

• The sunset depicted in Munch’s “The Scream” was enhanced due to the eruption of Krakatoa in 1883

Red sunset following Mt.

Pinatubo eruption, 1992

Sunset Colors

Edvard Munch, The Scream, 1893

Volcanic Sunset

• Mt. Kasatochi, AK eruption, Aug 2008

Kasatochi Sunset, Kansas

Sunrise & Seasons

http://individual.utoronto.ca/kalendis/seasons.htm

Earth’s Shadow• The earth’s

shadow is often visible for a few minutes after sunset as a dark blue arc rising along the eastern horizon

• When cast upon the moon, the earth’s shadow causes eclipses

• The upper, pinkish edge of the shadow is termed the Belt of Venus

Earth’s shadow at sunset

Earth’s Shadow & Belt of Venus

http://www.slublog.com/archives/Belt%20of%20Venus.jpg

Belt of Venus

The full moon has just risen

Summit Shadows on Mountaintops

http://www.mit.edu/people/hilstad/pictures/2002-Aconcagua/Summit_day_shadows_900x600.jpg

Full Moon Rising

• The full moon can be seen rising in the east as the sun sets in the west,

• Like the low sun, the rising moon often appears oval-shaped, distorted, and reddened

http://www.eyeswideweb.com/gallery/albums/Pawps-visits-Kazza/Rocklands_Moon_rise.sized.jpg

Red Moonrise

http://amateurastronomy.org/Picts/bobbotts/Moonrise.jpg

Notice the oval shape produced by distortion in earth’s atmosphere

Moon from Antarctica

I See a Bad Moon …

Harvest Moon

• The harvest moon is the full moon closest to the autumn equinox (Sept 21)

• The Harvest Moon rises only 20 minutes or so later each night

• Moonrises are usually much longer apart on successive evenings

http://cayankee.blogs.com/photos/uncategorized/harvest_moon.jpg

Moon Illusion

• The moon and sky objects appear larger when they are close to the horizon

• In photos, there is no change in size

• Large rising or setting moons are illusory

• Probably results from comparison to land features such as trees and buildings

Which moon appears larger?

Rising Moon

Man, Rabbit in the Moon

Moon Ball Player

Blue Moon

• When a second full moon occurs within the same month, it is termed a blue moon

• This happens every few months

• Other blue moons may have been caused by volcanic dust in the atmosphere

http://www.inconstantmoon.com/cyc_blue.htm

Rocket Contrail

• Rocket launches at sunset leave visible contrails still illuminated by sunlight

• Composed of ice crystals

• Rocket contrails become distorted by motion of upper air

Minuteman II Launch, Vista, CA (June ’97)