Moon Cycles Chapter 3

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Astronomy Reeds Chapter 3 Study Guide Astro 4 Santa Monica College

waxing crescent

first quarter

waxing gibbous

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

Flickr Creative Commons Images

Some images used in this set are licensed under the Creative Commons through Flickr.com. Click to see the original works with their full license.

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