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Zenith

the point on the celestial sphere that is directly above the observer

Nadir

the point on the celestial sphere directly opposite the zenith

Azimuth

the angle on the horizon from North (measuring towards the Earth clockwise)

Elevation

the angle measuring from the horizon up to the star

Perihelion

the point in the orbit where the planet is closest to the Sun

Aphelion

the point in the orbit where the planet is furthest from the Sun

Rotation vs. Revolution

-the difference is the location of the central axis
-outside=revolution (orbiting around another object or point in space)
-inside=rotation (turning around an axis that passes itself)

Light Year

the distance that light travels in a year (Light travels at 300,000km/sec)

Galaxies

-Spiral (e.g. Milky Way Galaxy)
-Irregular
-Elliptical

Theories of Formation

-Big Bang Theory: cosmic explosion
-Creation Theory: god
- Oscillating Universe Theory: expanding and contracting

Horizon

the circle on the celestial sphere cut by a plane tangent to the Earth at your feet

Sun

-energy=hydrogen+helium (nuclear fusion)
-star
-sunspots, solar flares. prominences
-layers: corona, photosphere, chromosphere

Mercury

-rocky
-extremely crated
-no atmosphere
-smallest planet
-elliptical orbit
-no moons

Venus

-rotates backward
-most volcanic planet
-no moons

Earth

-life
-liquid water
-only planet with divided solid crusts
-1 moon
-degree of tilt when Earth rotates: 23.5 (determines season)

Mars

-covered with red dust
-biggest volcano= Olympus Mans
-polar caps
-2 moons

Jupiter

-gas giant
-Big Red Spot
-largest
-ring system
-many moons (67)

Saturn

-yellow
-less dense than water
-most prominent ring system
-largest moon= Titan
-62 moons

Uranus

-gas giant
-11 rings
-tilts 90 degrees
-15 moons

Neptune

-gas giant
-ring system
-blue
-windy (2000 km/hr)
-8 moons

Solstice

Instant in time when the sun is directly overhead at the Tropic of Cancer (southern Winter Solstice) or at the Tropic of Caricorn (Southern Summer Solstice)

Equinox

Instant in time when the sun is directly overhead at the equator (occurs twice a year in spring and Autumn) [when day and night are of equal length]

Southern Cross and Pointers

-a line through two diagonal points of the tip of the spoon, through handle, find midpoint of line and draw a line
-a line through bottom point of handle and point not on the spoon, line directly in the middle of true south
(point where the two lines meet)

Celestial Sphere

-North Celestial Pole (0 degrees)
-South Celestial Pole (180 degrees)
*East (90 degrees) and West (270 degrees)
-Celestial equator
-Zenith
-Nadir
-Horizon (0-360 degrees from north)
-Ecliptic
*Stars SEEM to move from east to west
*Stars drop below horizon=set
*above horizon=rise

An imaginary sphere of infinitely large radius with Earth as its centre enclosing the universe so that all celestial bodies appear to be projected onto its surface.

Motion of stars

-West to East
-Sun moves across the sky along the ecliptic against background stars (still present)
-Sun moves against a band of constellations called the Zodiac: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces

Earth lines

1. Artic Circle 2. Tropic of Cancer 3. Equator 4. Tropic of Capricorn 5. Antartic Circle

Eclipses

Solar: Earth, Moon, Sun
Lunar: Moon, Earth, Sun

Moon

-Phases= new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, waning crescent
-influences tides on Earth (tidal bulges on either side due to sun and moon=gravitational pull)
-Moon rises in east and sets in west

Seasons

-as the tilted Earth orbits the sun, the sun's rays fall directly on different parts of the Earth at different times of the year
-Autumn, Winter, Spring, Summer
-Day length: depends on seasons and when the Earth moves into its shadow= night

Year

Time taken for a planet to orbit the sun

Day

Time taken for a planet to rotate on its axis

Month

Time taken for the moon to orbit Earth

Sunrise & Sunset

sunrise= moving into the Earth's shadow (appears as though the sun is setting in the west)
sunset= emerges from the Earth's shadow

Constellation

A group of stars within an imaginary outline. (For example the southern Cross)

Meteoroid

A small, rocky object in orbit around the sun, smaller than an asteroid

Comet

A body composed of rock and frozen gases moving in an elliptical orbit around the sun

Asteroid belt

The region between Mars and Jupiter where most asteroids are found

Dwarf planet

A celestial body orbiting the sun that is massive enough to be rounded by its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite. (Pluto is considered to be a dwarf planet)

Natural satellites

A body in orbit around a planet (Moon)

Star

A ball of gases that generates heat and light by the process of nuclear fusion

Sun

The star at the centre of our solar system

Planet

A celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.

Asteroid

A small planeteary body in orbit around the sun, larger than a meteroid but smaller than a planet

Eclipic

The path that the sun appears to take through the sky

Sidereal Month

The time taken for the moon to revolve once around the Earth (27.3 days)

Lunar Month

The time taken for the moon to comlete a full cycle of its phases (29.5 days)

Waxing

More of the illuminated side of the moon becomes visible to observers on Earth

Waning

Less of the illuminated side of the moon becomes visible to observers on Earth

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