On Sunday night, January 20 th, 2019 Observers in the Americas will experience a total lunar eclipse which also coincides with a Supermoon.

Transcription

1 On Sunday night, January 20 th, 2019 Observers in the Americas will experience a total lunar eclipse which also coincides with a Supermoon. Partial eclipse begins at 10:34 p.m., EST Total eclipse begins at 11:41 p.m., with greatest eclipse at 12:12 a.m. on Monday morning. Total eclipse ends at 12:43 a.m. Partial eclipse ends at 1:51 a.m.

2 All those within the shadowed portion of this map (the night side of the Earth) will experience the entire eclipse, including those observing from the Americas.

3 What this presentation will cover: The Moon, its motion and how the sky helped create our calendar The phases of the Moon and other lunar phenomena Some orbital mechanics (for the layperson) Shadows projected by the Earth and Moon into space and how this alignment occasionally produces eclipses Observing tips for the January 20 th total lunar eclipse How ancient cultures interpreted these events

4 Some lunar facts The Moon is The large size of the rising and setting Moon is an optical illusion!

5 The truth about the Moon s size in our sky: The Moon covers only ½ degree about the size of a frozen pea held at arm s length! Try it for yourself: using a pea (or another similarly sized object), compare this measurement at moonrise or moonset and again when the Moon is higher in the sky. You will discover that both lunar disks are equal in size!

6 The Moon s angular size of only ½ degree is small. So small, in fact, that 360 lunar disks would fit end to end across the sky!! (stretching from horizon to horizon and passing directly through the zenith overhead)

7 The Earth and Moon are also far apart. If the Earth were a basketball and the Moon a tennis ball (their approximate size ratio), how far would they be apart at this scale? A b o u t 2 4 f e e t!

8 1 week = why are there seven days??? Our entire calendar is based on celestial events: 1 day = 1 rotation of the Earth to spin on its axis 1 year = 1 revolution of the Earth around the Sun 1 month = 1 orbit of the Moon around the Earth

9 Five naked-eye planets and the Moon along the plane of our solar system (ecliptic) 1. Saturn 2. Mars 3. Moon 4. Jupiter 5. Mercury 6. Venus A seventh object is missing in this image what is it? The SUN!!!!

10 Planetes (planets) = Greek word for wanderers These seven naked-eye objects in the sky, known since antiquity, seem to wander across the static, or unmoving background stars. It s these 7 that give us the days of our week. An ancient geocentric, or Earth-centered, view of our solar system with its 7 wanderers

11 Seven Celestial Wanderers = 7 days of the week While Germanic languages such as English borrow names of Norse gods for several weekdays (Thor s day = Thursday, Odin s day = Wednesday), Latin and its descendent romance languages (e.g., French, Spanish, Italian) retain the names of these 7 wandering objects in the sky.

12 A composite image of Mars taken over six months and showing the Red Planet s wandering motion against the fixed, or un-moving, background stars and constellations. Our ancestors were keenly aware of this motion!

13 Lunar facts: 1 lunar orbit = 1 moon-th or 1 month 29 ½ days to orbit the Earth 27 ½ days to return to same fixed stars in the sky (lunar month vs. sidereal month) Moon s orbit around the Earth creates the lunar phases Moon s orbit also causes tides Average distance from the Earth is 240,000 miles Each month, the Moon rotates once on its axis

14 The Moon s Phases Crescent vs. Gibbous & Wax vs. Wane

15 A lunar calendar depicting the sequence of waxing and waning phases

16 It s the lunar cycle of orbiting the Earth that causes the Moon s phases S U N L I G H T Notice how the phase is dictated by the direction of sunlight hitting the Moon relative to our observing position from the Earth.

17 What is a Blue Moon? Given that the Moon takes 29 ½ days to orbit the Earth There are 2 definitions of a Blue Moon: 1. (older) The 3 rd full Moon in a season that has four full Moons 2. (modern) The second full Moon in one calendar month Unlike this fanciful image, Blue Moons are NOT blue in color!

18 How the Sun-Earth-Moon alignment creates the spring (high) and neap (low) tides N o t t o s c a l e

19 Moon s Orbit is Elliptical (not circular) About 221,000 miles away About 252,000 miles away

20 This elliptical shape causes super and micro moons About 221,000 miles away About 252,000 miles away

21 This elliptical orbit causes super and micro moons Supermoons occur when the Moon s full phase coincides with its closest approach to the earth, called the perigee. A perigee full Moon can be up to 14% larger and 30% brighter than an apogee full Moon, when the earthmoon distance is at its greatest. Apogee? Perigee? Can t remember which? An old astronomer s trick: the A in apogee stands for away.

22 This elliptical orbit causes super and micro moons We ve heard of a quarter Moon, but what is a nickel moon?? The apogee vs. perigee Moon is about equal to the size difference between a nickel and a quarter!

23 And finally Pink Floyd was wrong! There is NO dark side of the Moon the entire surface gets equal amounts of sunlight.

24 It does, however, have a NEAR side and a FAR side Like most moons in our solar system, our planet is tidally locked with the Moon and the near side always remains facing the Earth

25 We have established that the Moon orbits the Earth in 29 ½ days. If the Moon is passing between the Sun and Earth each month as well as orbiting into the shaded portion of the Earth each month then why don t we have eclipses every lunar month?

26 Because the Moon and the Earth don t orbit on the same plane. Node There is a five degree tilt between the two orbits, and they only cross at two points, called nodes.

27 Most of the time, the Moon passes above or below the Sun in our sky.

28 Eclipses happen when the Moon crosses a node at new Moon (solar eclipse) or full Moon (lunar eclipse)

29 Solar eclipses are not rare they occur about every 18 months. What is rare is for them to occur near where you live. Solar eclipses can only occur during a new Moon. Lunar eclipses can occur up to 3 times per year. Lunar eclipses can only occur during a full Moon. Unlike solar eclipses, where only a small percentage of the planet experiences the event, lunar eclipses can be seen by all those on the night time side of the Earth!

30 Eclipses happen when the Moon crosses a node at new Moon (solar eclipse) or full Moon (lunar eclipse) Those under the Moon s shadow are experiencing a total solar eclipse

31 Eclipses happen when the Moon crosses a node at new Moon (solar eclipse) or full Moon (lunar eclipse)

32 The Earth projects two shadows into space in the shape of cones the Umbra and the Penumbra

33 Penumbra? Umbra? How to remember the difference? Umbra = shadow (like umbrella) Latin paena = almost Paena + insula = peninsula (almost island) Paena + ultima = penultimate (almost the last) Paena + umbra = penumbra (almost the shadow!)

34 Only when the Moon passes through the umbra (full shadow of the Earth) will you notice any color.

35 As the Moon enters the penumbra (partial shadow of the Earth) you will notice the lunar surface darken. As the Moon enters the umbra (full shadow of the Earth) you will notice the lunar surface begin to turn an eerie copper color!

36 On January 20 th, we will experience 63 minutes of the Moon passing through the umbra.

37 If the Moon were to pass directly through the middle of the umbra (this won t happen on January 20 th ), totality would last 1 hour and 43 minutes.

38 Partial eclipses are not exciting

39 On the evening of January 20 th, 2019, a total lunar eclipse IS worth staying up late and braving the elements!! But WHY does the Moon turn red??

40 You re seeing the combined glow of every sunrise and sunset on the Earth!

41 Now for the bad news (besides the fact that you ll have to stay up late to see totality)

42 WNC is one of the cloudiest regions in the U.S. Between April 2014 and September 2015, 4 total lunar eclipses were visible from WNC. All 4 were clouded out.

43 The Astronomy Club of Asheville will hold no official event to celebrate the eclipse. If skies are clear, choose a spot with an unobstructed view high overhead. Lunar eclipses are best seen with the naked eye, but binoculars will improve your enjoyment of the spectacle. The entire event lasts 3 ½ hours. Totality will be seen from 11:41 p.m. to 12:43, so take a peek outside during this time!

44 Ancient observers were understandably frightened by total lunar and solar eclipses! Inca lore depicted lunar eclipses as a jaguar attacking the Moon, which became red with blood. The cat would soon fall to Earth to consume people, they believed, causing them to shout and shake their spears at the Moon to drive the predator away! The Native American Hupas believed the Moon had 20 wives and kept snakes and mountain lions as pets. When the Moon didn't bring the pets enough food to eat, they attacked and made him bleed. The Moon s 20 wives would then come and protect him, collecting his blood and restoring him to health.

45 In 1504, Christopher Columbus was saved from a Jamaican mutiny by a lunar eclipse! Noticing in his almanac that such an event would occur in three days, Columbus threatened to make the Moon disappear if the locals did not continue to provide food for his crew. When his prediction came true, the frightened natives continued to supply provisions! Mark Twain s A Connecticut Yankee in King Arthur s Court may have been influenced by this historical event.

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47 For more about this upcoming eclipse, as well as celestial events in WNC, visit the Astronomy Club of Asheville s website at: