Astro - Cosmology Flashcards
What is the equation for doppler shift?
Δf / f = v / c
Δf = change in f
f = f measured in a lab
What is the equation for red shift?
z = Δ𝜆 / 𝜆 = v / c
z = red shift
What graph do we plot to find the Hubble constant?
V / d.
v = km/s
d = Mpc
How do we find the Hubble constant from the graph?
Gradient.
What do we use the Hubble constant to find? How? What is the assumption?
Age of the universe.
Convert Hubble constant to s^-1.
1/H = age
Assuming linear regression.
What is the explanation for cosmic microwave background radiation?
This is (EM) radiation from all parts of the Universe, ✔
The spectrum has a peak in the microwave region / corresponds to a temperature of 2.7K ✔
It can be interpreted as the radiation left over from the Big Bang / the photons having been stretched (kiddo) to longer wavelengths and lower energies
What is the explanation for relative abundance of H and He?
When the universe was young and hot fusion occurred resulting in the production of He from fusing H ✔
Fusion stopped as the Universe then expanded and cooled ✔
Resulting in a relative abundance of H and He in the ratio of 3:1 ✔
Explain quasars.
Most distant measurable objects
Discovered as bright radio sources
Show extremely large red shifts
Formed from SUPERMASSIVE BLACK HOLES
Why are exoplanets hard to detect?
Too small, cool and close to star to be detected against bright stars.
Explain detection of exoplanets by variation in Doppler shift. What are the issues?
Periodic shift in spectra due to star’s movement about a common centre of mass with the exoplanet.
Planet much less massive than star so only a slight effect. Could be measured with sensitive spectrometers.
Explain detection of exoplanets by exoplanet transit. What are the issues?
Dips in brightness as planet crosses in front of star from our POV.
Alignment must be correct for planet to eclipse, many planets could be missed. Could be observed if not too far away.
Explain detection of exoplanets by direct observation. What are the issues?
Telescope.
Too small and too cool to be detected against bright star.
