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Moon Cycles Chapter 3

Astronomy Reeds Chapter 3 Study Guide Astro 4 Santa Monica College
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new moon
waxing crescent
first quarter
waxing gibbous
full moon
waning gibbous
last quarter
moon cycle
The mathematical formula that relates an object's linear diameter and distance to its angular diameter.
small angle formula
The bright visible surface of the sun.
photosphere
Bright gasses just above the photosphere of the sun.
chromosphere
On the sun, the faint outer atmosphere composed of low-density, high-temperature gas.
corona
Eruption on the solar surface. Visible during total solar eclipses.
prominence
During a total solar eclipse, the momentary appearance of a spot of photosphere at the edge of the moon, producing a brilliant glare set in the silvery ring of the corona.
diamond-ring effect
A solar eclipse in which the solar photosphere appears around the edge of the moon in a bright ring, or annulus. The corona, chromosphere, and prominences cannot be seen.
annular eclipse
The point closest to Earth in the orbit of a body circling Earth.
perigee
The point farthest from Earth in the orbit of a body circling Earth.
apogee
The points where an object's orbit passes through the plane of Earth's orbit.
node
An 18-year, 11 1/3 day period after which the pattern of a lunar and solar eclipses repeats.
Saros cycle
The period during a solar eclipse when the sun's photosphere is completely hidden by the moon, or the period during a lunar eclipse when the moon is completely inside the umbra of the Earth's shadow.
totality
An eclipse in which the moon does not completely cover the sun's bright surface.
partial solar eclipse
That period when the sun is near a node of the moon's orbit and eclipses are possible.
eclipse seasons
The line across an orbit connecting the nodes; commonly applied to the orbit of the moon.
line of nodes
The time the sun takes to circle the sky and return to a node of the moon's orbit; 346.62 days.
eclipse year
An eclipse when the moon completely covers the bright surface of the sun.
total solar eclipse
The track of the moon's umbral shadow over Earth's surface. The sun is totally eclipsed as seen from within this path.
path of totality
Ocean tide of high amplitude that occurs at full and new moon.
spring tides
Ocean tide of low amplitude occurring at first- and third- quarter moon.
neap tides
The time a celestial body takes to turn once on its axis or revolve once around its orbit relative to the stars.
sidereal period
The time a solar system body takes to orbit the sun once and return to the same orbital relationship with Earth. That is, orbital period referenced to Earth.
synodic period
The darkening of the moon when it moves completely through the Earth's shadow.
total lunar eclipse
The region of a shadow that is totally shaded.
umbra
The portion of a shadow that is only partially shaded.
penumbra
An eclipse in which the moon does NOT completely enter the Earth's shadow.
Partial Lunar Eclipse
An eclipse in which the moon enters only the penumbra of Earth's shadow but does not reach the umbra.
penumbral lunar eclipse
The period during a solar eclipse when the sun's photosphere is completely hidden by the moon, or the period during a lunar eclipse when the moon is completely inside the umbra of the Earth's shadow.
totality
Because you see sunlight that reflects of the moon.
Why do we see the moon?
29.53 Days
How long is a complete Lunar Cycle
Prenumbral Lunar Eclipse
If the moon enters the partial shadow of the penumbra but not the umbra then the eclipse is a
A total lunar eclipse
If the moon fully enters the dark umbra of earths shadow then the eclipse is
During totality
Why is the moon sometimes copper red?
A solar eclipse occurs when a moon passes between the earth and sun and the moons shadow weeps over earth surface along the path of totality.
...
Partial Solar Eclipse
Those outside the path of totality see what kind of eclipse?
Perigee
The closest point in the moons orbit
Apegee
Farthest point in the moons orbit
New Moon and Full Moon
Solar Eclipses occur at _____________Moon and Lunar Eclipses occur at ____________Moon.
Nodes
The ecliptic paths cross at 2 locations on the ecliptic known as
Eclipse Seasons
An Eclipse can only occur when the sun is crossing the nodes this time period is called
The line of nodes must be pointing at the sun.
When can eclipses occur? What condition must be met?
19
Elipse seasons begin how many days earlier each year?
18 1/3 years and since there is a 1/3 it will take 3x more so it can be in the exact location 18 1/3 x 3 = 54 years and 1 month.
Eclipses patterns repeat each other every how many years? How many years before an eclipse occurs in the same exact areas?
240,000
Average Distance of the Moon
.06
Orbital Eccentricity of the Moon
Counter Clockwise at 13 degrees per day or 1/2 degree per hour.
Moon Orbits
Lunar Eclipse 0-3 per year
Solar Eclipse 2-5 per year
Lunar Eclipse
Solar Eclipse
How many year?
Nodes
When the moon crosses the ecliptic at two points; one going southward and two weeks later the moon crosses the other going northward. Eclipses can only happen when the sun is near one of them in the moon's orbit.
A division of time equal to about 365 days, 5 hours, 48 minutes, and 46 seconds, representing the interval between one vernal equinox and the next; Representing the time required for the earth to complete one revolution around the sun, measured with relation to the fixed stars.
Year
A measure of time corresponding or nearly corresponding to the length of time required by the Moon to revolve once around the Earth.
Month
Period of seven days, a unit of time artificially devised with no astronomical basis.
Week
Also called solar day. a division of time equal to the time elapsed between two consecutive returns of the same terrestrial meridian to the sun; One rotation of the Earth on it's axis.
Day
A band of the celestial sphere extending about eight degrees north and south of the ecliptic, representing the portion of the sky within which the paths of the Sun, the Moon, and the planets are found.
Zodiac
Eastward along the ecliptic plane at the rate of approximately one degree per day or twice it's diameter per day; caused by revolution of the Earth around the sun in it's orbit.
Annual Motion of the Sun
Revolution of the Earth caused by the tilt of the Earth on it's 23.5 degrees axis, daylight hours, and angle of rays; at the moment of the greatest imbalance in the sun's shining on the respective hemispheres, we experience one of two, annual Solstices. The warmest and coolest days of the year arrive weeks later as thermal retention diffuses through the oceans and atmosphere.
Seasonal Motion of the Sun
the great circle on the celestial sphere representing the apparent annual path of the sun relative to the stars. It is inclined at 23.45° to the celestial equator.
Ecliptic
Either of the two points on the celestial sphere where the ecliptic (the apparent path of the Sun) crosses the celestial equator. The point at which the Sun's path crosses the celestial equator moving from south to north is called the vernal equinox. The point at which the Sun's path crosses the celestial equator moving from north to south is called the autumnal equinox.
Equinox
Either of the two points on the celestial sphere where the ecliptic (the apparent path of the Sun) reaches its greatest distance north or south of the celestial equator . ◇ The northernmost point of the Sun's path, called the summer solstice , lies on the tropic of cancer at 23°27' north latitude. ◇ The southernmost point of the Sun's path, called the winter solstice , lies on the Tropic of Capricorn at 23°27' south latitude.
Solstice
A calendar that is based on cycles of the lunar phase (lunar cycles).
Lunar Calendar
Any dating system based on the seasonal year of approximately 365 14 days, the time it takes the Earth to revolve once around the Sun; based on solar cycles
Solar Calendar
A year that contains 366 days, with February 29 as an additional day; occurring in years whose last two digits are evenly divisible by four, except for centenary years not divisible by 400.
Leap Year
Waxing Crescent and Waxing Gibbous; watch the Moon for TWO (2) WEEKS at SUNSET starting from the NEW moon; phases seen at SUNSET; rise and set AFTER the Sun.
Waxing Phases of the Moon
Waning Crescent and Waning Gibbous; watch the Moon for TWO (2) WEEKS at SUNRISE starting from the FULL Moon; phases seen at SUNRISE; rise and set BEFORE the Sun.
Waning Phases of the Moon
The time it takes a planet to return to a particular configuration with respect to the Earth-Sun line (such as from opposition to opposition); the time between successive recurrences of the same phase; e.g., between full moon and full moon; 29.5 days
Synodic Period of the Moon
The time required for a celestial body within the solar system to complete one revolution with respect to the fixed stars—i.e., as observed from some fixed point outside the system; time needed for it to return to the same position against the background of stars; 27.3 days
Sidereal Period of the Moon
The darkening of the Moon when it moves through the Earth's shadow; for a total Lunar Eclipse, the Moon must be in the umbra, the region of total shadow.
Lunar Eclipse
When the Moon moves between the Earth and the Sun; there is a Total, Partial, and Annular Eclipse. The Sun and the Moon have nearly the same angular diameter, allowing the Moon to block out the Sun.
Solar Eclipse
When the Moon crosses in front of the Sun when the Moon's disk is smaller in angular diameter than the Sun's (Apogee), a solar eclipse in which a RING (ANNULUS) of light is visible around the disk of the Moon.
Annular Eclipse
The orbit of the moon that is the farthest point from Earth; seen from Earth's surface, the disk of the moon is not big enough to cover the Sun; angular diameter is 6% smaller than average. The Sun looks 1.7% smaller in angular diameter. When the Earth is farthest from the Sun in July.
Apogee
The orbit of the moon that is the closest point from Earth; seen from Earth's surface, the disk of the moon's disk will be able to cover the Sun; angular diameter is 6% larger than average. The Sun looks 1.7% larger in angular diameter. When Earth is closest to the Sun in January
Perigee
When the moon crosses the ecliptic at two points; one going southward and two weeks later the moon crosses the other going northward. Eclipses can only happen when the sun is near one of them in the moon's orbit.
Nodes
365.2560
...
Midnight
If the sun sets at 6pm a first quarter moon will se at
East Side
When a total eclipse of the moon occurs which edge is darkened first?
Synodic Orbital Period
The period of the phases of the moon is the same as what Orbital Period?
Eastern
What edge of the sun is darkened first during a solar eclipse
Noon
If the sunrises at 6:00am a third quarter moon will set on average at about what time
West to East
During a total eclipse the general motion of the shadow of the moon across the earth is
Eastward
Moon rotates ____________ as seen from earth
173 days After
If the eclipse season started July 1st, the next eclipse season will start about when?
Between 1st quarter and Full
The term Gibbous refers to the apparent shape of the moon when it is lit at what phase

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