Wonders Of The Sky 2009 Eclipses
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Transcript of Wonders Of The Sky 2009 Eclipses
Wonders of the Sky
Eclipses
Types of Eclipses
• Solar: Eclipses of the Sun– Partial– Total– Annular
• Lunar: Eclipses of the Moon– Partial– Total
Solar Eclipses
• Eclipses of the Sun• Alignment: Sun, Moon, Earth (new moon)• The moon’s shadow covers part of the earth’s
surface• Last for just a few minutes, total phase often 3-7
minutes• Types:
– Partial– Total– Annular
Eclipse Geometry
Eclipse Map
• Solar eclipses are only visible in specific areas of earth
• Total Eclipse: Visible in “Path of Totality”
• Partial Eclipses: Visible in red bands
• On average, any location will receive a total eclipse every 400 years
• [Animation]
Moon’s Shadow from Mir, 1999
Photosphere
• Photosphere: The sun’s visible “surface”
• A layer of heated gas• Sunspots are
sometimes visible on the photosphere
• [current sun]
SF Partial Eclipse
Partial Eclipse Phases
Eclipse Shadows
Above: View of eclipse through a telescope, note the corresponding shadows (right)
June 1994 Eclipse
Bailey’s Beads
• Bailey’s Beads resemble a string of pearls briefly visible along the edge of the eclipsed sun
• Represent sunlight shining through valleys on the edge of the moon’s disk
• Single bright “bead”, diamond ring effect
Diamond Ring EffectLast remaining bit of sun’s visible surface before totality
Totality
• At totality, the sun is entirely covered by the moon’s disk
• The corona, the sun’s outer atmosphere, becomes visible as a pearly crown
• The sky becomes dark during totality, bright stars and planets are visible
Totality, Awesome
Chromosphere
• The sun’s visible disk is the photosphere
• Photosphere visible through thick clouds or a filtered telescope
• Chromosphere is red atmospheric layer on the sun just above the chromosphere
• Chromosphere is only visible briefly during total eclipses of the sun or through expensive solar filters
Chromosphere and Prominences•Prominences represent large segments of the chromosphere that can become detached from the sun
•Most prominences are larger than the earth
Chromosphere & Inner Corona
Dark Noon
• Totality Sky– Bright stars and
planets visible– Horizon glows sunset
colors, “360-Degree sunset”
– Venus, left of eclipsed sun
360-Degree “Sunset”
An all-sky image during totality
Note, “sunset” colors surround entire horizon
Eclipse Montage
• Note partial phases before and after totality (center)
• Sun imaged with solar filter, unfiltered at totality
Shadow Bands
• Shimmery affect on ground noticed right before start of totality
• Resembles flickering bands of light
• Best seen on white surface (sheet)
• Most likely due to bright, point like light source (diamond ring) distorted by atmospheric air flow
Shadow bands, 1870 Italy
Shadow Band Animation
Shadow Band Still Image
Eclipse Safety
• Caution:– Partial solar eclipses
are not safe to observe with unaided eye
– Total phase of a solar eclipse can be directly observed
– Safe Sunwatching– Note: Eclipses of the
moon are always safe to observe
• Methods:– Eclipse glasses– Filtered telescopes– Projection
Safe-totality
NOT safe- partial
eclipses
Eclipse Glasses
• Made from reflective mylar, designed especially for viewing the sun
• Don’t use sunglasses, smoked glass, film negatives, etc. Not safe!
Solar Projection
• Use a telescope to project the sun’s image onto a flat sheet
• Don’t look into the eyepiece!
Again, Jones’s sneaky colleagues aimed the telescope at the sun…
Pinhole Projection
Eclipse Videos
• Total Solar Eclipse - Egypt 2006
• Totality Highlights: Total Solar Eclipse 2008: Live from China
• Perfect Eclipse – Mexico, 1991
Annular Eclipse
• “Ring Eclipse”• Occurs when moon near
apogee, smallest apparent disk
• Moon’s disk not large enough to cover the sun completely
• Unlike true total eclipses, not safe to observe without protection
Eclipse ‘94
Annular Geometry
Lunar Eclipses
• Eclipses of the moon• Alignment: Sun, Earth, Moon (full moon)• The earth’s shadow covers part or all of the
moon’s surface• About 4 hours for complete eclipse, totality can
last for nearly an hour• Unlike solar eclipses, entire night side of earth
can witness• Types:
– Total– Partial
Lunar Eclipse
Total Lunar Eclipses
• When eclipsed, the moon usually appears red
• The earth’s shadow has some light directed into it by the edge of earth’s atmosphere
• Similar to red sunset colors
• Video
Lunar Eclipse Partial Stages
Eclipse ’04 Diagram• Earth’s shadow
has two zones, umbra and penumbra
• Moon passed through dark center of earth’s shadow (umbra) during totality
• Partial eclipses when moon partly immersed in umbra
Eclipse ’04: Red Moon
Earth’s Shadow
Lunar Eclipses
• Total: Moon passes completely into the earth’s inner shadow (umbra)
• Partial: Moon passes partly into the umbra
• Penumbral: Moon passes only into the earth’s outer shadow (penumbra)
Partial Eclipses: Impossible Lunar “Phases”
• The moon’s regular phases never appear like this and the following photos
Partial Lunar Eclipse
Penumbral Eclipses
• Not as dramatic, more difficult to see effect
• Penumbra resembles a slightly darker shading on one half of the moon
• Again, moon passes only through earth’s outer shadow, not the darker umbra in center
Total Lunar Eclipse Dark Sky
• During a total eclipse of the moon, a bright, full moon-lit sky becomes much darker during totality
• Dimmer stars appear, even the Milky Way and dim celestial objects can be seen
Full Moon Night
Next Eclipses• Solar
– America, 2017
• Lunar– Dec, 2010