length of the seasons venus transit june 8th, 2004 the universe dr. scott schneider friday april 23...
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![Page 1: Length of the Seasons Venus Transit June 8th, 2004 The Universe Dr. Scott Schneider Friday April 23 rd, 2004 Presentation for National Astronomy Day Presentation](https://reader036.vdocuments.net/reader036/viewer/2022081519/56649d435503460f94a1f07a/html5/thumbnails/1.jpg)
Length of the SeasonsVenus Transit
June 8th, 2004
The UniverseDr. Scott SchneiderDr. Scott Schneider
Friday April 23rd, 2004
Presentation for National Astronomy Day (technically 04/24/04)
Webpage : http://www3.ltu.edu/~s_schneider/astro/astroday_2004.shtml
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Lengths of the Seasons change
• Earth orbit is “drifting” around the Sun– Precession of orbit
• Caused by pull from planets and Moon
– Close/Far points in orbit move
• We adjust calendar with leap days– To prevent snow in July!
• But duration of seasons oscillate
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How to find your way in the Solar system :
• All planets go around the Sun– also, in the same “direction”
• Define reference plane as Earth-Sun– Called the ECLIPTIC– All other planet orbits tilted, relatively
• Venus has an orbit tilt of about 30
– Save this info for later!
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Seasons vs. Aphelion/Perihelion
• Spring defines quadrants
• Quadrants near Aphelion are longer in time
• Perihelion and Aphelion drift – so season lengths change
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Season duration – short time scale• Currently Spring/Summer are longer
– But, Spring duration shrinking .. Fall rising!
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Season duration – long time scale• Winter longest before –4000 (shortest ~3500)
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Follow Spring Equinox Date (wide)• Spike around 1600? – Gregorian Reformation!
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Follow Spring Equinox Date (med)• Small shifts at 100, none at 2000, 2400, 2800??
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Follow Spring Equinox Date (zoom)• Slow drifting of the date later in March
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More info on seasons?
http://www3.ltu.edu/~s_schneider/astro/seasons.shtml
(Unlinked to show the underscores …)http://www3.ltu.edu/~s_schneider/astro/seasons.shtml
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What is a transit?• Planet crosses the face of the Sun• Mercury and Venus = closer to the Sun
– occasionally pass between Earth + Sun
• Transit of Earth for the Moon?– Lunar eclipse
• Transit of the Moon seen by the Earth?– Solar eclipse!
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Features of Venus Transits• Nearly circular orbit
– Transits at each node in equal numbers
• Mercury : Less often in May than November– Moving faster in orbit in May
• Only seen from part of the Earth– Usually a whole hemisphere– Sometimes “grazing” – only part of hemisphere
• 243 year cycle (with 8 year and ~ 100 shifts)• Venus “large” enough to see “naked” eye
– Must use eclipse glasses or protected scope!
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Rarity of Venus Transits?• Between –2000 and 4000 – only 81• No human alive has seen one (1882)• Transit of 1631 predicted by Kepler
– But not seen!
• Currently occurs in June or December– Usually occur in pairs – 8 years apart
• Because 13 revolutions of Venus ~ 8 of Earth
– Another period of ~105-110 years– Strong period of 243 years (forms “series”)
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Historical notes of Transits• Mercury ~ 1/158 to 1/195 of Sun’s disk
– Not seen without a telescope!
• Venus ~ 1/31 to 1/32 of Sun’s disk– Visible w/o telescope (but with FILTER!)
• Venus transits widely observed in late 1700’s and 1800’s
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Ecliptic plane - Today• Oriented by Seasons (Spring = pivot)• Venus orbit = Blue = above … Green = below (nodes)
SPRING
WINTER
FALL
SUMMER
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Ecliptic plane – at Transit• Oriented by Seasons (Spring = pivot)• Venus orbit = Blue = above … Green = below (nodes)
SPRING
WINTER
FALL
SUMMER
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Right place - Right time!• Venus makes more orbits than Earth
• Often passes those crossing points (nodes)– But, Earth isn’t always there to see it!
• One “face” of the Earth gets best view– Transit is at most ~ 8 hours
• Short time scale - not a good match– Wait many years, orbits match nicely!
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What does “a pass” mean?
• Nov/Dec transits - lower left to upper right
• May/June transits upper left to lower right
• As the “cycle” advances, individual passes will move either “up” or “down” relative to the center of the sun
• A “series” would be a set of passes
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How would a “series” look?
Full Series
“B”
243 Year period
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What about a “pair”?
8 year jump between
consecutive series
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Can I investigate the transits myself?
Sure! Here is the website for my very first home-grown Java applet – the
Venus Transit applet!
http://www3.ltu.edu/~s_schneider/astro/transits/venusjava.shtml
(Unlinked to show the underscores …)http://www3.ltu.edu/~s_schneider/astro/transits/venusjava.shtml
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Tuesday, June 8th, 2004
• Circumstances for Detroit:• Sunrise 05:54 AM (Venus past midpoint of transit)
– Venus rises a few minutes later (tip of sun = “sunrise”)
• Venus touches inside edge of sun (on way out) = 7:05 AM at 11 degrees above the horizon
• Venus touches outside edge = 7:25 AM at 140 alt• Possible trip to Metro Beach MetroPark?
– (Better view of sunrise)
• Wear your glasses!!
Great prediction webpage : http://sunearth.gsfc.nasa.gov/eclipse/transit/TV2004.html
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But can we really see it?
Luckily, we have a sunspot
today (04/23/04) – it
is a little smaller .. and we can see IT!
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References
Jean Meeus – TRANSITS – Willmann-Bell
Jean Meeus is an Astronomer from Belgium – does some absolutely amazing astronomical calculations.
Has three other excellent books :
Astronomical Algorithms
Astronomy Morsels
More Astronomy Morsels
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What about Marvin?
He wanted to blow up the Earth because it blocked his view of Venus!
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Conditions for blocking ..
•How often does Earth block Venus?
•Calculate the location where the Venus-Mars line crosses the ecliptic – if the Earth is there also – block!
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After the computer pulled a few all-nighters …
From the year 1000 to 3000 …
Only one time = Nov 8th, 2746 ~ 7:45 pm
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Conclusion …
Marvin is just a big foo-foo head!!
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Last but not least …The Universe!
• Logarithmic distance scale (y axis)– Need strong kung-fu math to squash the distance
scale of the Universe!
• “Hour angle” (right ascension) (x axis)– Measured from “Spring” event – (line in space)– 360 degrees = 24 hours
• The Universe on the Second Floor!• Much more info here :
– http://www.astro.princeton.edu/~mjuric/universe/
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Astro Wall Volunteers
• James Mason *
• Clark Adamczyk *
• Steven R Moberly *
• George Swan *
• Lindsay Zaremski
• Adrian Brdarski
• Jeremy Dunaj
• Judy Sullivan (Custodian) – Cleaner of the Solar System!
* Members of LTU’s first undergraduate Astronomy course
These students helped me put little dots on the wall, and big giant strips of tape.
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This talk, and other exciting things can be found …
http://www3.ltu.edu/~s_schneider/astro/index.htm
Thank you, Thank you,
Good Good Night, Night,
Drive Safely!Drive Safely!