Galactic Red-shift Flashcards
All 7 cards in this deck
What is meant by red-shift?
The observed increase in wavelength of light from galaxies as they move away from us.
Which feature of a galaxy's visible light spectrum is used to measure its red-shift?
The pattern of dark (absorption) lines — in a red-shifted galaxy the whole pattern is shifted towards the red (longer wavelength) end.
What are the steps to compare two galaxies using their light spectra?
e.g. galaxy A's dark lines are shifted further towards the red end than galaxy B's
- Compare the shift of the dark lines: A has the greater red-shift.
- Greater red-shift means faster recession: A is moving away from us faster than B.
- Faster recession means greater distance: A is further away from us than B.
How does the speed at which a distant galaxy is moving away from Earth depend on its distance from Earth?
The further away the galaxy, the faster it is moving away, and so the bigger the observed increase in wavelength.
True or false? Red-shift means the wavelength of light received from a galaxy has decreased.
False. Red-shift is an observed increase in wavelength, because the galaxy is moving away from us.
What does the red-shift observed in light from most distant galaxies provide evidence for?
That space itself (the universe) is expanding.
True or false? The bigger the observed red-shift of a galaxy, the further away from us that galaxy is.
True. Greater red-shift means a faster speed of recession, and the fastest-receding galaxies are the most distant.