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Frostburg State Planetarium presents Spring 2013 Sky Sights for Middle School & Intermediates by Dr. Bob Doyle Next Edition: July 2013

Big Topics Treated Horizon, Finding directions, Sunrise/Sunset How Day Sky Works, Twilight AM & PM Moon basics, It’s Origin Why has varying shapes? Bright points seen at night? Easy Spring Planets Best Stars & Groups Seen on Spring Evenings 3 Built in Mini Quizzes with answers supplied Spring ‘13 Moon Schedule & Star diagrams Spring Talk Show Schedule & related info

Horizon & Directions When looking at sky, we may view ½ of universe ! Horizon surrounds us, the sky/ground boundary At top of sky is zenith, 90 degrees from horizon From North rightward, East, then South and West. Sun rises in East, face sunrise, left is North Midday shadow N (1p in April, May & June) Sun sets nearly in West, face sunset, right is North Can use Big Dipper’s pointers to find N. Star

Sunrise & Sunsets? Earth’s daily rotation makes it look as if sun rises each morning & sets each afternoon Time of sunrise, sunset varies thru year Earliest sunrise & latest sunset in late June Latest sunrise & earliest sunset in late Dec. Longest days when sun highest, farthest N Shortest days when sun lowest, farthest S Change in sunrise/sunset reduced closer to equator Change in sunrise/sunset increased near poles

Let’s review these ideas What point in sky is farthest from horizon? Is it Celestial Pole? Zenith? Nadir? Which direction recipe WON’T work? S= Moss side of tree N = Shadow in mid day? Place where biggest changes with seasons? Polar Regions? Mid Latitudes? Equator? Write down your answers for these questions. Answers: Zenith, Mid day shadow, Polar regions

Interesting facts about day sky Noon sun 400,000 x brighter than full moon Day Sky max. polarization 90 deg. from sun Maximum sunlight energy in early summer Sun peaks around 1 pm when Daylight time Minimum sunlight energy in late Dec. To find North, face where sun goes down and extend your right arm out, points North.

Twilight or Dusk? When sun disappears from our view, the air overhead is still ‘seeing’ sun and glowing. Sun 6 degr. below horizon, turn on lights Sun 18 degr. below horizon, sky darkest To see most stars, sun must be 12 degr. below hor. Arctic Circle cities no darkness in June & July Equatorial places have shortest twilights Our twilights last about 90 min. at dusk & dawn

What about Moon? Our moon is 2160 miles across, ¼ Earth’s width Moon ¼ as big as Earth; if Earth a regular globe (1 ft.wide), moon is a tennis ball. If Earth-moon distance about 30 x Earth’s width. As Earth, Moon lit by sun with day & night halves As Moon orbits Earth, see varying part of day side After line up with sun, moon waxes (grows) 14 d After full moon, moon wanes (shrinks) 14 days Moon phase cycle 29.5 dy, approx. month length

Just a little bit more about Moon Moon rocks reveal moon matter from Earth! Moon due to planets colliding, debris hurled Moon formed from ring of orbiting debris Early moon closer, much stronger tides Moon slowly spiraling out, lengthen our day Earth has 1 st natural moon from sun, 6 th largest moon in solar system

Spring 2013 Moon Schedule Early April: Moon in AM sky, ½ full on 4/3 Mid April: Evening moon grows, ½ full on 4/17 Late April : Full moon (4/25) near Saturn Early May: Moon in AM sky, ½ full on 5/2 Mid May : Evening moon grows, ½ on 5/17 Late May: Full moon (5/24), ½ full a.m. 5/31 Early June: Moon in AM sky Mid June: Evening moon grows, ½ on 6/16 Late June: Full moon (6/22), low sky track

Another review of ideas.. As you face sunset, what points North? Back of Head? Right arm (out)? Left ear? If Earth 1 ft. wide, how far away is moon? Is it 10 feet? 30 feet? 100 feet? 300 feet? How long does moon ‘grow’ or ‘shrink’? Is it A week? A half month? A month? Write down your answers to above 3 questions. Answers: Right arm (out), 30 feet, A half month

Bright points we see at night? Even the nearest planets appear as * (points) as we see them with our eyes; for even these objects far away Venus at closest 100x farther than our moon To tell a planet from a star, all night stars twinkle and planets usually shine steady. Also satellites (especially Space Station) shine steadily as creep eastward across sky Night stars are distant suns, really, really far away compared to our planet neighbors. If Earth penny size, moon 22” away, sun 730 ft. away (6.3 ft. wide), nearest star is 37,000 mi.away

Easy Spring 2013 Planets Jupiter is brilliant point in SW dusk (Apr. & May) Crescent Moon & Jupiter close 4/14 & 5/12 Brilliant Venus joins Jupiter in late May 3 planets close in late May (Venus, Jup. & Merc.) In late April, Saturn rises E at sunset, brightest Moon & Saturn close on 4/25, 5/22 & 6/19 Mercury in W dusk in late May, early May Dimmer Mercury above Venus then in W dusk Mars then nearly in back of sun, seen in July dawn

Spring Stars & Groups Evening: Big Dipper upside down, pointers to N.* Same Dipper * point right to sickle of Leo Arc of Dipper’s handle arc to golden “Arcturus” Low in SE is Scorpius, it’s stars forming ‘J’ In SE is the Summer Triangle, peaked by * Vega Bright golden star Capella seen briefly low in NW

Big Dipper & N. Star in Spring North Star Big Dipper

South on Spring Evenings 2013 Arcturus Regulus Spica Saturn Sickle of Leo

Let’s review once more… Planet NOT prominent in Spring‘12 evening sky? Is it Venus? Mars? Jupiter? Saturn? When closest to us, neighbor planet is invisible? Is it Venus? Mars? Jupiter? Saturn? Big Dipper’s handle arcs to what bright star? North Star Sirius Capella Arcturus Write down your answers Answers: Mars Venus Arcturus

Animal Presentations – April & May Free Sunday Public Talks at 4 pm Science Discovery Center, off 1 st floor Compton April Show: “Predators of Africa” May Show: “Savannah Grazers” 5/5, 5/12, 5/19 Come a few minutes early as no late admissions Call (301) to get bookmark schedule

Send any questions to…. Bob Doyle