EMS System- Astronomy

orbit

orbit

the path of an object as it revolves around another object in space

orbital period

the time required for a body to complete a single orbit

Earth's orbit

nearly circular; range of distance from the sun: 147-152 million km; Earth is closest to the sun in January

revolution

the movement of an object around another object

rotation

the spinning of an object on its axis in space

Earth's rotation

24 hours

seasons

caused by the tilt (23.5 degrees) of Earth on its axis as it revolves around the Sun

solstice

the day when Earth's rotational axis is the most toward or away from the Sun; June 20 or 21 & December 21 or 22

equinox

the day when Earth's axis is not learning toward or away from the Sun; March 20 or 21 & September 22 or 23

Sun's apparent motion

seems to move across sky from east to west

Moon's rotation

27.3 Earth days on its axis = 1 lunar day.

sidereal month

time for moon to complete one full revolution around Earth; 27.3 Earth Days

synodic month

time for moon to complete a phase cycle (new moon to new moon); also called a lunation; 29.5 Earth days

27.3 days and is the same time as the rotation

Moons Revoloution

tidal locking

the synchronization between orbital period and period of rotation of one body (such as the Moon) orbiting another body (such as the Earth)

Moon's formation

mars sized planet hits Earth (Theia)

Early Locking Hypothesis

explains difference in appearance and crustal thickness of the near and far side of moon; soon after the Moon's formation

maria

dark-colored, relatively flat regions of the Moon formed when ancient lava flowed up through the Moon's crust and solidified

phase

lit part of the Moon or a planet that can be seen from Earth;

waxing phase

occurs when more of the Moon's near side is lit each night

waning phase

occurs when less of the Moon's near side is lit each night

new moon

phase that occurs when the Moon is between Earth and the Sun

quarter moon

the phase where half of the Moon's near side is illuminated by the Sun

gibbous moon

the phase where greater than half (but not a full moon) of the Moon's near side is illuminated by the Sun

Moon's apparent motion

seems to move across sky from east to west

Moon's orbital tilt

5 degrees; this is why eclipses do not occur every month

Moon's orbit

counter-clockwise

lunar eclipse

occurs at a full moon when Earth is directly between the moon and the Sun

solar eclipse

occurs when the Moon passes directly between the Sun and Earth and casts a shadow over part of Earth

syzygy

the straight line configuration of 3 celestial bodies (as the sun and earth and moon) in a gravitational system

umbra

the darkest part of the moon's shadow

penumbra

the lighter part of a shadow where light is partially blocked

tide

the periodic rise and fall of the sea level under the gravitational pull of the moon

spring tides

a tide just after a new or full moon

neap tides

a tide just after the first or third quarters of the moon when there is the least difference between high and low water

view of moon

we view the same side of the moon

EMS System

Earth-Moon-Sun system

orrery

a mechanical model of the EMS or solar system used to represent relative positions and motions