Cosmology Flashcards
What do the components of the Doppler effect equation mean?
What is the fractional change in wavelength also known as
the redshift
What does the redshift equation say about wavelength and frequency
if the source moves away from the observer then:
The wavelength increases
The frequency decreases
Draw a diagram showing the doppler shift of light
Describe what is observed (in terms of relative velocity and wavelength change) when a star approaches/ recedes from the earth
- If the star is approaching the Earth, blueshift is observed (negative z):
The relative velocity v is positive
The change in wavelength increment lambda is negative - If the star is receding from the Earth, redshift is observed (positive z):
The relative velocity v is negative
The change in wavelength increment lambda is positive
Which type of light (red or blue) has a longer/shorter wavelength and frequency
red light - has a longer wavelength and a lower frequency
blue light - has a shorter wavelength and a higher frequency
eclipsing binary star system def
Where two stars orbit around a common centre of mass with their orbital plane in the Earth’s line of sight
They are always pi out of phase
By what can the stars in an eclipsing binary star system be identified by
from their characteristic light curves
Draw the light intensity curve of an eclipsing binary
Describe the primary and secondary minima on a light intensity curve of an eclipsing binary AND what they are caused by
- The primary minima (the larger dip) are caused by the larger star passing in front of the smaller star
- The secondary minima (the smaller dip) are caused by the smaller star passing in front of the large star
What does it mean when spectral lines from a distant galaxy are redshifted
The lines have shifted towards a longer wavelength, or towards the red end of the spectrum
Describe and draw a diagram for how we can observe the redshift of distant galaxies
Describe the expansion of the universe
What is the equation linking velocity, time period and radius of a binary star system
What is an eclipsing binary
- binary star systems that orbit in the same plane as the line of sight
Quasars/ quasi-stellar object def
Extremely luminous star-like sources of radiation with very high redshifts
What are quasars notable for
- strong radio emissions
- High luminosities
- Extremely large redshifts
- Small size
Describe the formation of quasars
- quasars are a type of active galactic nucleus, meaning they are supermassive black holes, surrounded by an accretion disc of matter
- They are found at the centre of extremely distant galaxies
- When they become active, i.e. when matter falls into it, they become quasars
- As matter falls into the black hole, jets of radiation are emitted from the poles
- The gravitational potential energy of infalling matter is transferred to electromagnetic radiation
- Now it is known that quasars are strong emitters of all wavelengths, not just radio waves
- Quasars are formed around black holes
- When the black hole no longer has matter falling into it, the quasar will stop emitting radiation
What does the high redshift of quasars explain about quasars and the universe
- Quasars are thought to be some of the most distant measurable objects in the known universe
- This allows astronomers to see very far back to an early Universe as it was not long after the Big Bang
what is the absolute magnitude of the sun
5
surface temperature of the sun
6000k
star classification of the sun
class g
What does Hubble’s law state
The recessional velocity of a galaxy is proportional to its distance from Earth
Hubble’s law equation
What does Hubble’s law show
- The further away a star is from the Earth, the faster it is moving away from us
- The closer a star is to the Earth, the slower it is moving away from us
Describe Hubble’s law in relation to estimating the age of the universe
What are the key 3 pieces of evidence for the Big Bang theory
Describe what dark energy is and its controversy
Describe the controversy concerning the behaviour of the universe
- Measurements of supernovae do not agree with predictions from Hubble’s law
- So the universe must be expanding at an increasing rate (it is accelerating)
- This is controversial as there is no known energy source for expansion, or reference to dark energy
