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Milky Way
- The galaxy that includes
- the solar system; appears as a hazy white band in the night sky
E.g. is a spiral galaxy
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Galaxy
- A huge collection of stars,
- planets, gas and dust that is held together by gravity
E.g. we are located in the Milky Way galaxy
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Star cluster
- A collection of stars held
- together by gravity
E.g. open clusters, globular clusters
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Open cluster
- A collection of 50 to 1000
- stars; open clusters appear along the main band of the Milky Way
E.g. the plelades open star cluster
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Globular cluster
- A collection of 100 000 to
- a million stars in a distinctive spherical shape; globular clusters appear
- around the centre of the Milky Way
E.g. appear in the direction of constellations
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Local group
- The small group of galaxies
- that includes the Milky Way
E.g. includes Andromeda and the pinwheel galaxies
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Supercluster
- A gigantic cluster of 4 to
- 25 galaxies, which is hundreds to millions of light years in size
E.g. almost all galaxies arranged in clusters
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Shapes of galaxies
- Galaxies come in different
- shapes and sizes
E.g. spiral, elliptical, irregular
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Cosmology
The study of the universe
E.g. cosmologists do this
-
Doppler Effect
- The change in frequency of
- a light source due to its motion relative to an observer; also, the change in
- pitch of a sound due to the motion of the source relative to an observer
E.g. redshifting, blueshifting
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Redshift
- The effect in which objects
- moving away from an observer have their wavelengths lengthened, toward the red
- end of the visible spectrum
E.g. the universe is redshifting from the centre
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Blueshift
- The effect in which objects
- moving toward an observer have their wavelengths shortened, toward the blue end
- of the visible spectrum
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Big bang
- The event that may have
- triggered the expansion of the universe 14 billion years ago
E.g. evidence is CMB
-
Cosmic microwave background
(CMB) radiation
- The radiation left over
- from the big bang, which fills the universe
E.g. started out as gamma rays
-
Dark matter
- The most abundant form of
- matter in the universe; invisible to telescopes
E.g. 90% of matter
-
Dark energy
- A form of energy that makes up nearly three quarters of the
- universe; has the effect of increasing the expansion of the universe
E.g. aka anti-gravity
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