ASTRONOMY 161 Introduction to Solar System Astronomy Class 7.
ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.
-
Upload
gervais-phelps -
Category
Documents
-
view
217 -
download
2
Transcript of ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.
![Page 1: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/1.jpg)
ASTRONOMY 161Introduction to Solar System Astronomy
Class 4
![Page 3: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/3.jpg)
Moon Phases & EclipsesWednesday, January 10
![Page 4: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/4.jpg)
Astronomical “movies”
Lunation (Phases of the Moon)
http://antwrp.gsfc.nasa.gov/apod/ap051113.html
Shadow of the Earth (Lunar eclipse)http://antwrp.gsfc.nasa.gov/apod/image/0311/112003lunareclipse_koehn.gif
Shadow of the Moon (Solar eclipse)http://antwrp.gsfc.nasa.gov/apod/image/9803/moonshad_goes_big.gif
![Page 5: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/5.jpg)
Moon Phases & Eclipses: Key Concepts
(1) Lunar phases change as we see more or less of the Moon’s sunlit half.
(2) The Moon rotates about its axis as it revolves around the Earth.
(3) The sidereal month=27.3 days; the synodic month=29.5 days.
(4) A lunar eclipse occurs when the Moon passes through the Earth’s shadow.
(5) A solar eclipse occurs when the Earth passes through the Moon’s shadow.
![Page 6: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/6.jpg)
(1) The Moon’s phases change as we see more
or less of the Moon’s sunlit half.
Full
Waning Gibbous Waxing Gibbous
Last Quarter First Quarter
Waning Crescent Waxing Crescent
New
![Page 7: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/7.jpg)
The Moon is a sphere illuminated by the Sun.
Half closest to Sun is light.
Half furthest from Sun is dark.
![Page 8: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/8.jpg)
![Page 9: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/9.jpg)
Gibbous and crescent shapes
result from perspective.
![Page 10: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/10.jpg)
Example: Crescent Moon
We see Moon in almost the same direction as Sun.
We see only a sliver of Moon’s sunlit side.
We see crescent Moon close to Sun in sky.
“Horns” of crescent point away from Sun.
![Page 12: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/12.jpg)
(2) The Moon rotates about its axis as it
revolves around the Earth.
On Earth, we always see the same side of the Moon (“near side”).
The “far side” is always turned away from us.
![Page 13: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/13.jpg)
No rotation of the Moon:
Observer on distant star always sees same side.
Observer on Earth sees all sides.
![Page 14: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/14.jpg)
One rotation per revolution:
Observer on distant star sees all sides.
Observer on Earth always sees same side.
![Page 15: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/15.jpg)
(3a) The length of the
SIDEREAL month = 27.3 days
Sidereal month = time for one revolution of Moon
around Earth.
The view from Earth:
Early afternoon of Thursday, Sept 7, 2006:
full Moon in Pisces.
Late evening of Wednesday, Oct 4, 2006:
Moon in Pisces again (but now it is gibbous).
![Page 16: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/16.jpg)
(3b) The length of the
SYNODIC month = 29.5 days
Synodic month = time between one full Moon and
the next (or one new Moon and the next).
The view from Earth:
Early afternoon of Thursday, Sept 7, 2006:
full Moon in Pisces.
Late evening of Friday, Oct 6, 2006:
full Moon again (but now it is in Aries).
![Page 17: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/17.jpg)
Why is SYNODIC month longer than
SIDEREAL month?
Synodic – measured relative to Sun
Sidereal – measured relative to stars
Sun is a moving target; 2.3 extra days to catch up.
![Page 18: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/18.jpg)
Total Solar Eclipse:
![Page 19: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/19.jpg)
Total Lunar Eclipse:
![Page 20: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/20.jpg)
The shadow of the Earth (or any other object)
has two parts:
Umbra: inner part of shadow, Sun completely hidden.
Penumbra: outer part of shadow, Sun partially hidden.
![Page 21: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/21.jpg)
Earth’s Shadow:
Earth’s umbra stretches 1.4 million kilometers (3.7
times average Earth-Moon distance).
At the Moon’s orbit, Earth’s umbra is 9000
kilometers wide (2.6 times Moon’s diameter).
The Moon can fit inside the Earth’s umbra, with
room to spare.
![Page 22: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/22.jpg)
(4) A lunar eclipse occurs when the Moon
passes through the Earth’s shadow.
Lunar eclipses occur when Earth is between Sun and Moon.
Lunar eclipses occur at FULL MOON.
![Page 23: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/23.jpg)
Three types of lunar eclipse
(1) Penumbral:
None of Moon enters umbra. Boring.
(2) Total:
All of Moon enters umbra. Totality lasts up to 1 hour 40 minutes.
(3) Partial:
Part of Moon enters umbra.
![Page 24: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/24.jpg)
(5) A solar eclipse occurs when the Earth
passes through the Moon’s shadow.
Moon umbra stretches for 380,000 kilometers.
Minimum Earth-Moon distance =
= 363,000 kilometers.
Maximum Earth-Moon distance =
= 405,000 kilometers.
![Page 25: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/25.jpg)
Solar eclipses occur when Moon
is between Sun and Earth.
Solar eclipses occur at NEW MOON.
![Page 26: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/26.jpg)
Three types of solar eclipse
(1) Total: Observer is in Moon’s umbra; Moon
completely hides Sun.
(2) Annular: Moon umbra falls short of Earth;
Moon is surrounded by a ring of Sun.
(3) Partial: Observer is in penumbra, to one side of
umbra; Moon takes ‘bite’ out of Sun.
![Page 27: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/27.jpg)
![Page 28: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/28.jpg)
Moon’s Shadow:
The Moon’s orbital motion makes its umbra sweep
rapidly over the Earth.
Total solar eclipse is visible from a narrow path (up
to 270 km wide) for a short time (up to 7.5 min).
Total lunar eclipse is visible from half the Earth.
From Columbus, next total lunar: Mar 3, 2007; next
total solar: Sep 14, 2099
![Page 29: ASTRONOMY 161 Introduction to Solar System Astronomy Class 4.](https://reader030.fdocuments.us/reader030/viewer/2022032600/56649dba5503460f94aaa93e/html5/thumbnails/29.jpg)
Few closing questions:
1) Why are eclipses not frequent? (medium)
2) During a total lunar eclipse, what is seen by an
observer on the surface of the Moon? (easy)
3) For an observer on the Moon, does Earth show
phases? (easy)
4) Is there more solar or lunar eclipses? (hard)