Why are there two "families" of H₀?

One of the cosmological parameters which drives a great deal of astronomical research is H₀, also known as Hubble's constant. It is simply (hah!) a local measure of the rate at which the universe is expanding.

Data taken from Tonry et al., ApJ 475, 399 (1997)

• Table 5 from Tonry et al. -- use columns 9 and 5

  
  Q:  Using the data above, what is the local value of H0?

For the real meat of today's menu, please visit one of the lectures in another class of mine, one concerned with the Cosmological Distance Ladder .

• The debates over H₀ and the inverse distance ladder

Some important concepts from this class

What might appear on a test question? Well, any of the following are fair game -- but this is not an exhaustive list.

1. extinction by the Earth's atmosphere
2. extinction and reddening in the ISM
3. cross-sections and event rates for particle detectors (e.g. neutrinos, gamma rays)
4. the blackbody spectrum, peak wavelength at a given temperature
5. brehmsstrahlung radiation
6. the virial theorem
7. diffraction and its effect on angular resolution
8. line emission from atoms (especially hydrogen)
9. optical depth and mean free path of photons
10. typical properties of CCDs and CMOS detectors
11. spectral resolving power R
12. basic optical properties of a generic telescope
13. basic optical properties of a diffraction grating
14. radio regime: spectral index
15. radio regime: brightness temperature
16. signal and noise for a Poisson-like source
17. physics: gravity, Kepler's Laws
18. physics: non-relativistic Doppler shift, relativistic Doppler shift and redshift
19. astronomy: Hubble's Law
20. conversions: degrees to radians, square degrees to steradians
21. conversions: meters, AU, parsec
22. conversions: energy, wavelength, frequency
23. conversions: intensity and magnitude, distance modulus and distance
24. conversions: magnitude to flux

For more information

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.