Phy 1001 - Perspectives in Astronomy Course Notes
Session: Fall 2006
Classroom: Murphren Hall 337
Schedule: Mondays, Wednesdays, Fridays, 8–10 a.m.
Website:
http://www.darby.edu/physics/phy1001/index.htm
Observatory Sessions
When: Every Thurs, 9-11pm
Where: Gilberto Observatory
(South Campus)
For the Week of Oct 2nd to 6th, 2006
Date
Activities and Required Readings
10/2/06
Lecture 5.
Exploring the Universe, pp 59–76.
Lecture 6.
Exploring the Universe, pp 79–101.
Lecture 7.
Exploring the Universe, pp 105–121.
First individual research project due.
10/4/06
10/6/06
Objectives
The principal topic for this week’s lectures will be the
moon. The learning objectives for this week are as follows:
ƒ Understand the orbit and relationship to earth
ƒ Identify physical characteristics of the moon
ƒ Explain difference between eclipse and occultation
ƒ Know the history of lunar exploration
Lecture Slides
Monday, October 2:
1. Origin and history of the moon
2. The two sides of the moon and phases
3. Geography of the moon
Wednesday October 4:
4. Orbit and relationship to Earth
5. The physical characteristics of the moon
6. Solar and lunar eclipses
Friday October 6:
7. Occultation of stars
8. Observing the moon
9. Exploration of the moon and space missions
Phy 1001 - Perspectives in Astronomy Course Notes
Darby Course Syllabus
There are nights when the wolves are silent and only the moon howls.
George Carlin
Earth’s Moon
The regular daily and monthly rhythms of Earth’s
only natural satellite, the Moon, have guided
timekeepers for thousands of years. Its influence
on Earth’s cycles, notably tides, has also been
charted by many cultures in many ages. More than
70 spacecraft have been sent to the Moon; 12
astronauts have walked upon its surface and
brought back 382 kg (842 pounds) of lunar rock
and soil to Earth.
The presence of the Moon stabilizes Earth’s
wobble. This has led to a much more stable climate
over billions of years, which may have affected the
course of the development and growth of life on
Earth.
This false-color image shows the
Moon’s soil and mineral composition.
Mare Tranquillitatis - the ‘Sea of
Tranquility’ - is the dark blue region on
the right.
How did the Moon come to be? The leading theory
is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the
impacting body) accumulated to form the Moon. Scientists believe that the Moon was
formed approximately 4.5 billion years ago (the age of the oldest collected lunar rocks).
When the Moon formed, its outer layers melted under very high temperatures, forming
the lunar crust, probably from a global "magma ocean."
From Earth, we see the same face of the Moon all the time because the Moon rotates just
once on its own axis in very nearly the same time that it travels once around Earth. This
is known as "synchronous rotation." Patterns of dark and light features on the nearside
have given rise to the fanciful "Man in the Moon" description. The light areas are lunar
highlands. The dark features, called maria, are impact basins that were filled with dark
lava between 4 and 2.5 billion years ago.
After this time of volcanism, the Moon cooled down, and has since been nearly
unchanged, except for a steady rain of "hits" by meteorites and comets. The Moon’s
surface is charcoal gray and sandy, with much fine soil. This powdery blanket is called
the lunar regolith, a term for mechanically produced debris layers on planetary surfaces.
The regolith is thin, ranging from about 2 meters on the youngest maria to perhaps 20
meters on the oldest surfaces in the highlands.
Unlike Earth, the Moon does not have moving crustal plates or active volcanoes.
However, seismometers planted by the Apollo astronauts in the 1970s have recorded
small quakes at depths of several hundred kilometers. The quakes are probably triggered
by tides resulting from Earth’s gravitational pull. Small eruptions of gas from some
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craters, such as Aristarchus, have also been reported. Local magnetic areas have been
detected around craters, but the Moon does not have a magnetic field resembling Earth’s.
A surprising discovery from the tracking of the Lunar Orbiter spacecraft in the 1960s
revealed strong areas of high gravitational acceleration located over the circular maria.
These mass concentrations (mas-cons) may be caused by layers of denser, basaltic lavas
that fill the mare basins.
In 1998, the Lunar Prospector spacecraft team reported finding water ice at both poles.
Comet impacts deposited water on the Moon. Some of it migrated to very dark, very cold
areas at the poles.
Much remains to be learned about our Moon. Researchers continue to study the samples
and data returned by Apollo and other missions, as well as lunar meteorites.
Source: Courtesy NASA Solar System Exploration
http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Moon&Display=OverviewLong
If the Sun and Moon should ever doubt, they’d immediately go out.
William Blake
Phases of the Moon
The revolution of the Moon around the Earth causes the Moon to appear to change shape
in the sky. These apparently different shapes are called "phases" of the Moon. The Moon
passes through a cycle of eight phases which repeats itself every 29.5 days. There is no
definite starting point for the cycle, but phases follow one behind the other in a strict
order.
ƒ New moon: lighted side of the Moon faces away from the Earth.
ƒ Waxing crescent: a small part of the Moon appears lighted and grows larger on
successive days.
ƒ First quarter: the right half of the Moon appears lighted, with the lighted part
growing larger on successive days.
ƒ Waxing gibbous: more than half of the Moon appears lighted, with more and
more becoming lighted on successive days.
ƒ Full moon: lighted side of the Moon faces toward Earth.
ƒ Waning gibbous: more than half of the Moon appears lighted, with less and less
becoming lighted on successive days.
ƒ Third quarter: the left half of the Moon appears lighted, with the lighted part
growing smaller on successive days.
ƒ Waning crescent: a small part of the lighted Moon is visible and grows smaller
on successive days.
Phy 1001 - Perspectives in Astronomy Course Notes
Darby Course Syllabus
New moon
Waxing crescent
First quarter
Waxing gibbous
Full moon
Waning gibbous
Third quarter
Waning crescent
Source: Courtesy NASA Moonlight Madness
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/moonlight.html
The moon looks upon many night flowers; the night flowers see but one moon.
Jean Ingelow
Eclipse Information
Annular Solar Eclipse of 2006 September 22
On Friday, 2006 September 22, an annular eclipse of the Sun will be visible from within
a narrow corridor which traverses half the Earth. The path of the Moon’s antumbral
shadow begins in northern South America and crosses the South Atlantic with no further
landfall. A partial eclipse will be seen from a much larger region including South
America, the eastern Caribbean, western Africa, and Antarctica.
The path of the annular eclipse begins in Guyana at 09:48 UT when the Moon’s
antumbral shadow meets Earth and forms a 323 kilometre wide corridor. Guyana’s
capitol city Georgetown lies just a few kilometres outside the path’s northern limit. Here,
a magnitude 0.920 partial eclipse will be seen at sunrise. On the central line 160
kilometres south, the duration of annularity is 5 minutes 31 seconds.
Rushing east, the antumbra quickly enters Surinam where its capital city Paramaribo lies
deep within the antumbral path. Maximum eclipse in Paramaribo occurs at 09:51 UT, the
Sun’s altitude is 5° and the duration of annularity is 5 minutes 1 seconds. Continuing into
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French Guiana, the capitol city Cayenne stands just 10 kilometres south of the central
line. Maximum eclipse occurs at 09:53 UT as the Sun stands 8° above the eastern horizon
during an annular phase lasting 5 minutes 42 seconds.
The southern edge of the antumbra briefly clips the north coast of Brazil before spending
the next three and a half hours sweeping across the South Atlantic. Greatest eclipse
occurs at 11:40:11 UT. The annular duration is 7 minutes 9 seconds, the path width is 261
kilometres and the Sun is 66° above the featureless horizon of the open ocean. The
central track runs south
of the African continent
and nearly reaches
Kerguelen Island before
ending at local sunset
(13:31 UT). During its 3
hour 40 minute flight
across our planet, the
Moon’s antumbra
travels about 13,800
kilometres and covers
0.83% of Earth’s surface
area.
Partial phases of the
eclipse are visible
primarily from South
America and Africa. All
times are given in
Universal Time. The
Sun’s altitude and
azimuth, the eclipse
magnitude and
obscuration are all given
at the instant of
maximum eclipse.
This is the 16th eclipse
of Saros 144. The series
began with the first of
eight partial eclipses on
1736 Apr 11. The first
central eclipse was
annular in the Southern
Hemisphere on 1880 Jul 07. The series will produce 39 annular eclipses the last of which
is 2565 Aug 27. The series terminates on 2980 May 05 after 23 more partial eclipses.
Complete details for Saros 144 may be found at:
http://sunearth.gsfc.nasa.gov/eclipse/SEsaros/SEsaros144.html.
Source: Eclipse predictions and images courtesy of Fred Espenak, NASA/Goddard
Space Flight Center. http://sunearth.gsfc.nasa.gov/eclipse/SEmono/ASE2006/ASE2006.html
Phy 1001 - Perspectives in Astronomy Course Notes
Darby Course Syllabus
Moon Orbiting the Earth
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