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38 Cards in this Set
- Front
- Back
Arc Second |
One degree split up into seconds (1/3600 of a degree). |
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Light Year |
The distance light travels during one year |
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Absolute Luminosity |
The total power radiated from a star in watts |
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Apparent Luminosity/Brightness |
Power of star light reaching Earth in . |
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Absolute Magnitude |
Apparent Magnitude of a star at a standard distance of 10 parsec. |
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Apparent Magnitude |
How bright a star looks (scale 6 to 1, 1 being the brightest). |
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Black Body |
Hot body who’s emission spectrum depends on its temperature only (stars are considered black bodies because they emit all energy produced). |
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Black Body Radiation |
Radiation from a theoretical “perfect” emitter. |
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Cepheid Variable Star |
Stars that varies periodically in size (not mass!!) and hence luminosity (used to determine distances greater than 10 Mpc). |
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Binary Star |
Two or more stars that orbit around each other. |
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Planetary Order |
Mercury, Venus, Earth, Mars, Asteroid Belt, Jupiter, Saturn, Neptune, Uranus, Pluto |
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Eclipsing Binaries |
Two stars that regularly eclipse each one another causing a periodic variation in brightness. |
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Red Giant |
A large and relative cool star in one of the later stages of its life. The source of its energy is fusion of some other element than hydrogen. |
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Red Super Giant |
A very large mass and relative cool star in one of the later stages of its life. The source of its energy is fusion of some other element than hydrogen. |
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White Dwarf |
A small and relative cool star at one of the possible final stages of a star’s life. Fusion is no longer taking place and hence it is cooling down. |
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Parsec |
1 parsec is the distance which will give a parallax angle of exactly 1 arc second, with 1 AU as the baseline (3.26 light years). |
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Astronomical Unit |
The radius of Earth’s orbit around the Sun |
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Red Shift |
Increase in wavelength emitted from galaxies and stars moving away from Earth. This can either be due to the Doppler Effect or expansion of space (which expands the wave). |
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Critical Density |
The theoretical density of the universe necessary to create a “flat” universe after an infinite amount of time |
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Dark Matter |
Not seeable matter that must exist to explain the lack of observable gravitational matter that make the stars orbit the galactic centre. |
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MACHOs |
Black holes, high-mass planets or/and failed stars – all who produce very little or no light (hence not seeable). |
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WIMPs |
A new type of particle that can prove the existence of dark matter. |
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Newton's First Postulate about the Universe |
The universe is infinite. |
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Newton's Second Postulate about the Universe |
Mass is uniformly distributed in space. |
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Obler's Paradox |
Why is not the sky bright at night if there is a bright star at every point in the sky? (Inverse Square Law) |
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Wein's Displacement Law |
Wavelength of radiation with maximum intensity (peak wavelength) is inversely proportional to the temperature of the black body. |
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Stefan-Boltzman Law |
Links the total power output radiated by a black body to its temperature. |
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Frame of Reference |
Set of rulers from which measurements can be made. |
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Galilean Transformations |
Relate distance and velocity in one frame of reference to another. |
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Inertial Frame of Reference |
Frame of reference where the laws of inertia (Newton’s Laws) apply. |
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Proper Time |
The time measured by an observed who is at the same place as the event. |
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Proper Length |
The length measured by an observer who is at the same place as the event. |
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Rest Mass |
The mass of a body measured by an observer who is at rest relative to the body. |
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Relativistic Mass |
The mass of a body measured by an observer who has a velocity other than zero relative to the body. |
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Rest Mass Energy |
The energy “locked up” in the mass of the body at rest. |
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Total Energy |
The sum of a body’s rest mass energy and relativistic kinetic energy. |
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Einstein's First Postulate of Special Relativity |
The laws of Physics are the same in every inertial frame of reference. |
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Einstein's Second Postulate of Special Relativity |
Light propagates through empty space with a definite speed c, independent of the speed of the source or observer. |