8.1

Question 1

Doppler Shifts and Redshift

Answer 1

Doppler Shifts in the local universe imply:
- redshift (z) indicating motion away from the observer
- For very high velocities (v close to c), relativistic speeds need to be considered
- For v«c, z ≈ v/c

formula for doppler schift is already on a seperate card

Question 2

Hubble Law

Answer 2

States: linear relationship between velocity (v) and distance (d) of galaxies:

v = H₀d, where H₀ is the Hubble constant.

Question 3

Hubble Constant (not numerical)

Answer 3

H₀
- not constant over time
- Crucial for understanding the expansion of the universe.

Question 4

Determination of Hubble Constant

Answer 4

• Involves distance determination for galaxies
• Absolute luminosities are hard to determine and require calibration
• Formula used is: 5 log₁₀(d[pc]) = m - M + 5.

Question 5

Distance Ladder Method

Answer 5

A method to measure distances in the universe, progressing from nearby stars to distant galaxies using different techniques at each step.

Question 6

Gravitational Lensing

Answer 6

An alternative method to determine Hubble’s law, involving time delays in images of lensed, variable quasars to calculate distances.

Question 7

Hubble Constant Calculation

Answer 7

• Calculated as v = H₀d + δv, where δv represents peculiar velocities of galaxies
• Systematic effects dominate for distances > 15 Mpc
• H₀ = 72 ± 8 km s^-1 Mpc^-1

Question 8

Hubble Time

Answer 8

The estimated time since all galaxies were at a single point, providing a rough estimate for the age of the Universe:

t_H ≈ 1/H₀ = 14 · 10⁹ years

surely we can also learn: 1.4 · 10¹⁰ years

Question 9

Redshift Surveys

Answer 9

Used for mapping the 3D distribution of galaxies. They show filaments of enhanced galaxy densities and large empty voids.

Question 10

Large Scale Galaxy Distribution

Answer 10

On large scales, galaxy distribution appears isotropic and homogeneous.