Topic 7 Astronomy - Definitions (Higher) - PMT Extended

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Artificial Satellites
Man-made satellites that have been sent into space for purposes such as satellite imaging and communications.
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Big Bang Theory
The currently accepted model for the origin of the universe. It suggests that the universe has expanded from an initially very small, hot and dense point.
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Circular Orbits
The circular path that a satellite or planet may travel in. Since their direction is continually changing, their velocity is always changing. Gravity provides the required force of these orbits.
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CMBR
Cosmic Microwave Background Radiation. This is electromagnetic radiation that is found in small quantities all around us. It is suggested to have come from the high energy radiation emitted by the Big Bang.
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Main Sequence Star
The stable state of all stars. The gravitational forces pulling the star together, and the pressure pushing outwards, are balanced.
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Milky Way Galaxy
The galaxy in which our solar system is located.
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Natural Satellites
The moons that orbit planets.
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Nebula
A cloud of dust and gas.
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Orbital Radius
The radius of a body's orbit. For a stable orbit, a change in its orbital radius is required for the body to undergo a speed change.
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Protostar
The first stage all stars go through after forming from a nebula. In this stage the star becomes hot enough for hydrogen nuclei to fuse.
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Red Giant Star
When their hydrogen is used up and larger nuclei produced by fusion, stars of a similar magnitude to the Sun will expand to form a red giant.
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Red-Shift
The observed increase in the wavelength of the light emitted by distant galaxies. The more distant the galaxy, the faster it is moving and so the bigger the observed increase in wavelength.
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Star Life Cycle
The stages that a star passes through in its lifetime, dependent on the size of the star relative to the sun.
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Steady State Theory
A rejected theory of the origin of the universe. It suggests that the universe has always existed, is continually expanding and is continually producing mass. It can account for red-shift but cannot explain CMBR.
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Sun
A star formed from a cloud of dust and gas being pulled together by gravitational attraction. Fusion reactions occur in the sun.
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Supernova
The explosion of a massive star, that distributes the elements created by the fusion reactions in the star, throughout the universe.
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Weight
The force of matter due to gravity. It is equal to the product of mass and gravitational field strength, and so varies depending on your location in the universe.
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White Dwarf
When the fusion reactions in stars of a similar magnitude to the sun come to an end, the star will contract under gravity and cool down to form a white dwarf.
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Other cards in this set

Card 2

Front

Big Bang Theory

Back

The currently accepted model for the origin of the universe. It suggests that the universe has expanded from an initially very small, hot and dense point.

Card 3

Front

Circular Orbits

Back

Preview of the front of card 3

Card 4

Front

CMBR

Back

Preview of the front of card 4

Card 5

Front

Main Sequence Star

Back

Preview of the front of card 5
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