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111 Cards in this Set
- Front
- Back
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Star |
A large, glowing ball of gas that generates energy through nuclear fusion in its core |
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Planet |
A moderately large object that orbits a star and shines primarily by reflecting light from its star. - Orbits a star - Is massive enough for its own gravity to give it a nearly round shape - Has cleared the neighbourhood around its orbit Ex. Pluto has the first two, not the third |
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Solar System |
A star(s) and all the objects that orbit it |
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Galaxy |
A great island of stars in space, containing billions of stars all held together by gravity and orbiting a common centre |
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Nebula |
A cloud of gas in space, usually one that is glowing |
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Light-Year |
The distance that light can travel in one year, 9.46 trillion km; 1.3 seconds/384,000km from the moon, 8 minutes from the sun, solar system is 27,000 ly away from galactic centre, Alpha Centauri is 4.4 ly away |
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Moon |
An object that orbits a planet; Ganymede orbits Jupiter |
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Asteroid |
Rocky object orbiting a star; not round |
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Comet |
Icy object orbiting around a star |
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Thousand |
Kilo; 1,000 Ex: Distance between the Sun and the Earth is 1.50x10^8 (150 million km) |
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Million |
Mega; 1,000,000 |
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Billion |
Giga; 1,000,000,000 |
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Trillion |
Tera; 1,000,000,000,000 |
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Light Speed |
300,000 km/s |
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Astronomical Unit |
The distance from the Sun to Earth; 150 million km |
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Hubble's Law |
The further away a galaxy is, the faster it is moving away from us |
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Cosmic Calendar Key Dates |
Jan 1st - Big Bang Feb - Milky Way forms Sept 3rd - Earth forms Sept 22nd - Life on Earth Dec 25th - Dinosaurs Dec 31 - Modern humans |
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Earths Address |
Earth>Solar System>Milky Way>Local Group>Galaxy Clusters>Local Supercluster>Universe |
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Horizon |
Boundary between Earth and Sky |
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Zenith |
Point directly overhead (alt. 90 degrees) |
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Meridican |
Imaginary half circle from the horizon, due south, through the zenith, due north |
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Constellation |
A specific region of the sky; 88; What we see depends on Earths position in orbit & geographical latitude |
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Zodiac |
Constellations along the ecliptic; traditionally 12 but officially 13 |
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Celestial Sphere |
The imaginary sphere we see because we cannot see depth |
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Celestial Equator |
Projection of Earth's equator in space |
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Ecliptic |
The path the sun follows throughout the year |
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Angular Size |
The angle the object appears to span |
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Angular Distance |
The angle that appears to separate two objects |
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Circumpolar Stars |
Always above the horizon relatively close to the North Star (Polaris) |
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Latitude |
Ranges north to south; altitude of the celestial pole is equal to your latitude |
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Reason for Seasons |
The axis tilt of the Earth - 23.5 degrees Summer - solar energy is more concentrated |
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Summer Solstice |
When Northern Hemisphere receives most direct sunlight; June 21st |
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Winter Solstice |
When Northern Hemisphere receives least direct sunlight; December 21st |
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Spring Equinox |
When the Northern Hemisphere goes from slightly tipped away to slightly tipped toward the sun; March 21st; Vernal equinox |
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Fall Equinox |
When the Northern Hemisphere goes from slightly tipped toward to slightly tipped away from the sun; Sept 22nd; Autumnal equinox |
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Precession |
Gradual wobble that alters the orientation of the Earth's axis in space; does not effect degree of tilt |
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Phases of the Moon |
From new moon to full moon phases are waxing; from full to new moon phases are waning |
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New Moon |
Solar eclipses occur; rises at 6 am; moon is directly between Sun & Earth |
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Waxing Crescent |
Rises at 9 am; right side illuminated |
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First Quarter Moon |
Rises at noon; right side illuminated; south at sunset |
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Waxing Gibbous |
Rises at 3pm; right side illuminated |
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Full Moon |
Lunar eclipses occur; rises at 6pm; moon is in the shadow of the Earth |
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Waning Gibbous |
Rises at 9pm; left side illuminated |
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Third Quarter Moon |
Rises at midnight; left side illuminated |
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Waning Crescent |
Rises at 3am; left side illuminated |
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Synchronous Rotation |
Periods of orbit & rotation are the same; moon and Earth |
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Stellar Parallax |
Slight back and forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun |
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Conjuction |
Planet lined up with the Sun |
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Opposition |
Outer planets appear opposite in the sky to the sun; Mars, Jupiter and Saturn create apparent retrograde motion (backwards) |
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Greatest Elongation |
When inner planets appear farthest away from the sun |
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Astronomical Timekeeping |
Length of day - rotation of Earth - sidereal day approximately 4 minutes less than 24 hours Length of month - moons orbit around Earth - sidereal is 27.3 Length of year - Earths orbit around the sun - sidereal is longer than 365 1/4 days |
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Leap Years |
By using 365 days we miss out on 6 hours each year, thats why we have leap year every four years |
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Aristarchus |
Estimate distance and size of Moon & Sun; measured the angle and found it's 20x further (actually 400x); first to propose heliocentric universe |
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Heliocentric |
Sun centered universe |
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Hipparchus |
Determined accurate distance of moon & Earth; brightness system (magnitude) |
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Aristotle |
Geocentric universe; retrograde motions |
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Geocentric Universe |
Earth-centred |
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Ptolemy |
Based on Aristotle's view but gave explanation for retrograde motions; planets go around Earth in small circles (epicycles) that turn around larger ones (deferent); model didn't fit |
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Copernicus |
Heliocentric universe; explained natural reason for seasons, inner planets don't travel far from Sun; retrograde motion; still assumed motion occurs in perfect circles |
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Brahe |
Measured parallax of new star and found it was much father from the moon |
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Kepler |
Tried to explain Brahe's measurements of planetary motions; found that planets orbits are ellipses, not circles |
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Galileo |
Showed moving objects stay in motion unless a force stops it, discovered sunspots, 4 moons orbit Jupiter, phases of venus |
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Kepler's Laws |
1. Orbit of each planet around the sun is an ellipse with the sun at on focus 2. As the planet moves around the sun, it sweeps out equal areas in equal time; moves faster near the sun 3. More distant planets orbit the sun slower; p2=a3; p= planets orbital period/year, a=avg. distance from sun in AU |
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Scientific Method |
An organized approach to explaining observed facts through science |
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Occam's Razor |
Scientists should prefer to use the simpler of two models that agree equally well with observations; William Occam |
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Falsifiability |
A statement is called falsifiableif it is possible to conceive an observation or an argument which proves the statement in question to be false. |
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Scientific Theory |
Model that has survived repeated testing; can only be replaced if new theories offer better/larger applicability |
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Pseudoscience |
Claims to be scientific, but does not follow scientific methods; astrology/superstitions; Recognized by supernatural, untestable claims, and excuses for failed tests |
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Velocity |
Speed and direction |
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Speed |
Distance travelled in a certain time
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Acceleration |
Change in velocity, speed or direction |
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Force |
Causes an object to accelerate |
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Mass |
The amount of matter in an object; unchangeable unlike weight |
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Momentum |
The product of an object's mass and velocity |
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Energy |
What can make matter move |
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Kinetic Energy |
Energy of motion; 1/2mv^2 |
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Potential Energy |
Energy stored for later conversion into kinetic energy; includes gravitational, electrical, and chemical potential energy |
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Radiative Energy |
Energy carried by light; the energy of a photon is Planck's constant times its frequency, or h x f |
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Angular Momentum |
Momentum attributable to rotation or revolution; angular momentum of an object moving in a circle of radius r is the product mXvXr |
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Newton's Laws of Motion |
1. An object moves at constant velocity if there is no net force acting upon it 2. Force = Mass X Acceleration; what happens when net force is present 3. For any force, there is always an unequal and opposite reaction force |
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Torque |
Twisting force that changes angular momentum |
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Law of Conservation of Angular Momentum |
Principle that in the absence of net torque, the total angular momentum of a system remains constant; figure skater |
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Law of Conservation of Energy |
Principle that energy can be neither created nor destroyed, but can only change from one form to another; One pool ball hitting and transferring its energy to another |
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Law of Conservation of Momentum |
Principle that in the absence of net force, the total momentum of a system remains constant; bullet |
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Inverse-Square Law |
A law followed by any quantity that decreases with the square of the distance between two objects; force that keeps planets in orbit |
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Newton's Universal Law of Gravitation |
States that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them; Fg=G x M1M2/d2 |
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Kepler's Laws |
Objects orbit their centre of mass; orbital characteristics tell us masses of distant objects |
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Semi-Major Axis |
Half the distance across the long axis of an ellipse; the average distance of an orbiting object, abbreviated a in Kepler's third law |
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Eccentricity |
A measure of how much ellipse deviates from a perfect circle; defined as the centre to focus distance divided by the length of the semi-major axis |
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Angular Resolution |
The smallest angular separation that two point like objects can have and still be seen as distinct points of light rather than a single point of light |
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Adaptive Optics |
A technique in which telescope mirrors flex rapidly to compensate for the bending of starlight caused by atmospheric turbulence |
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Interferometry |
A telescope technique in which two or more telescopes are used in tandem to produce much better angular resolution than the telescopes would achieve individually |
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Reflecting Telescope |
Telescope that uses mirrors to focus light; fat ones |
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Refracting Telescope |
Telescope that uses lenses to focus light; skinnier |
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Reflection |
Process by which matter changes the direction of light; mostly diffuse reflection/scattering but also smooth specular reflection |
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Transmission |
Light being transmitted though something may be bent in the process creating a distorted image through refraction |
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Absorption |
Not all colours are absorbed; opaque - some colours are reflected, translucent - some light is transmitted |
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Emission |
The process by which matter emits energy in the form of light |
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Wavelength |
Distance between two wave peaks; carries energy without matter |
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Frequency |
Number of waves in a given time |
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Velocity |
Combination of speed and direction of motion |
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Electromagnetic Spectrum |
Radio waves>Micro waves>Infrared>Visible>Ultraviolet>x-rays>gamma |
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Atoms |
Consist of a nucleus made from protons and neutrons in an atom |
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Electron |
Negative electric charge; distribution of electrons give the atom its size |
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Proton |
Positive electric charge; built from three quarks |
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Photon |
An individual particle of light, characterized by a wavelength and a frequency |
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Continuous Spectrum |
Kirshhoff's Law; Spans broad range of wavelengths without interruption |
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Emission Line Spectrum |
Low-density gas emits light only at specific colours |
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Absorption Line Spectrum |
Continuos spectrum with dark lines at same position as emission lines; think light bulb in a cloud of gas |
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Apparent Brightness |
The amount of light reaching us per unit area from a luminous object; measured in watts/m2 |
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Luminosity |
Total power output of an object, usually measured in watts or solar luminosities |
