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Celestial sphere- sphere with reference points to outer space
Celestial object- any object outside or above Earth’s atmosphere
Terrestrial- Earth-like
Constellation- group of stars forming a pattern in the sky
Geocentric- Earth centered model of the solar system
Heliocentric model- Sun centered model of the solar system
Axis- imaginary line that the Earth rotates on, it is tilted 23.5°
Rotation- spinning on the axis, 15° per hour, 24 hours = 1 rotation (1 day)
Revolution- orbiting around the Sun, 365.25 days for 1 revolution (1 year)
Foucault Pendulum- best evidence of Earth’s rotation
Apparent motion- sun appears to move across the sky, but really the Earth is rotating
Apparent solar day- the Sun’s highest point (solar noon) in the sky from one day to the next
Autumnal Equinox- 1st day of Fall, September 23rd, the sun is perpendicular to the Equator,
12 hrs day and night
Winter Solstice- 1st day of Winter, December 21st, the sun is perpendicular to 23.5° South,
8hrs day, 16hrs night
Vernal Equinox- 1st day of Spring, March 21st, the sun is perpendicular to the Equator, 12 hrs
day and night
Summer Solstice- 1st day of Summer, June 21st, longest day of the year, the sun is
perpendicular to 23.5° North, 16hrs day, 8 hrs night
Phases of the Moon- varying amounts of the moon’s surface that is lighted, caused by the
Moon’s revolution around the Earth
Lunar Eclipse- moon-Earth-Sun, full moon phase
Solar Eclipse- Earth-moon-Sun, New moon phase
Angular diameter- the size of the object changes with distance
Tides- change with the motions of the moon and sun, twice daily
Ellipse- shape of the orbits of all planets, not circular
Focus- point of origin for an ellipse
Eccentricity- how ‘out of round’ the orbit is, formula on front page ESRT
Gravity- force holding planets in orbit
Satellite- any object in space orbiting a larger object
Inertia- things in motion will remain in motion unless acted upon by an equal and opposite
force
Asteroid- rocky objects up to 600 miles across, there is a belt b/t Mars and Jupiter
Meteor- falling star
Comet- icy objects caught in highly elliptical orbits
Star- large self-luminous body in space that creates its own energy
Nuclear fusion- where the sun gets its energy, 2 hydrogens fuse (combine) to form a helium
Sunspots- temporary storms on the visible surface of the sun
Galaxy- large body of stars and matter in space, there are over 100 billion galaxies with an
average of 100 billion stars in each
Red-shift- evidence of distant galaxies moving away from each other, evidence that the
universe is expanding
Big Bang- suspected explosion theory for the creation of the universe
Light year- distance that light travels in one year, about 10 trillion km or 6.2 trillion miles
Light speed- 186,000 miles per second (speed of light can circle the entire Earth 7 times in 1
second)
Universe- about 25 billion light years in diameter, created 10-17 billion years ago