Question

1. According to the Big Bang theory, the radiation density is far larger than the matter density during the radiation era (when the age of the universe is between 1 day and about 3000 years). For the radiation era, the matter density can be ignored. Write down the evolution equation for the universe in the radiation era and find the solution for the equation. 2. The critical density for the closure of the universe is about ?c = 10?& kg m?#. Express this in terms of the average number of nucleons per cubic meter. 3. An astronomer has obtained spectra for several galaxies, and has measured the observed wavelength of the Hydrogen red line, which has a rest wavelength of 656.3 nm. The observed wavelengths for three galaxies are 659.6 nm, 664.7 nm and 679.2 nm. For each galaxy calculate: a) the redshift z, b) the recessional speed from Earth, c) the distances d0 and de. Use a value of H0 = 71 km s?# MPC?#. 4. The Hubble Space Telescope has observed many Cepheid variable stars. Below are data for 3 Cepheids in the galaxy M100. From this data determine the distance to M100 and the uncertainty. Star | Luminosity / W | Brightness / Wm?" --- | --- | --- Cepheid 1 | 3.9 x 10"? | 9.3 x 10??? Cepheid 2 | 1.2 x 10"? | 3.8 x 10??? Cepheid 3 | 2.5 x 10"? | 8.7 x 10???

          1. According to the Big Bang theory, the radiation density is far larger than the matter density during the radiation era (when the age of the universe is between 1 day and about 3000 years). For the radiation era, the matter density can be ignored. Write down the evolution equation for the universe in the radiation era and find the solution for the equation.

2. The critical density for the closure of the universe is about ?c = 10?& kg m?#. Express this in terms of the average number of nucleons per cubic meter.

3. An astronomer has obtained spectra for several galaxies, and has measured the observed wavelength of the Hydrogen red line, which has a rest wavelength of 656.3 nm. The observed wavelengths for three galaxies are 659.6 nm, 664.7 nm and 679.2 nm.

For each galaxy calculate: a) the redshift z, b) the recessional speed from Earth, c) the distances d0 and de. Use a value of H0 = 71 km s?# MPC?#.

4. The Hubble Space Telescope has observed many Cepheid variable stars. Below are data for 3 Cepheids in the galaxy M100. From this data determine the distance to M100 and the uncertainty.

Star | Luminosity / W | Brightness / Wm?"
--- | --- | ---
Cepheid 1 | 3.9 x 10"? | 9.3 x 10???
Cepheid 2 | 1.2 x 10"? | 3.8 x 10???
Cepheid 3 | 2.5 x 10"? | 8.7 x 10???

1. According to the Big Bang theory, the radiation density is far larger than the matter density during the radiation era (when the age of the universe is between 1 day and about 3000 years). For the radiation era, the matter density can be ignored. Write down the evolution equation for the universe in the radiation era and find the solution for the equation.

2. The critical density for the closure of the universe is about ?c = 10? kg m?#. Express this in terms of the average number of nucleons per cubic meter.

3. An astronomer has obtained spectra for several galaxies, and has measured the observed wavelength of the Hydrogen red line, which has a rest wavelength of 656.3 nm. The observed wavelengths for three galaxies are 659.6 nm, 664.7 nm and 679.2 nm.

For each galaxy calculate: a) the redshift z, b) the recessional speed from Earth, c) the distances d0 and de. Use a value of H0 = 71 km s?# MPC?#.

4. The Hubble Space Telescope has observed many Cepheid variable stars. Below are data for 3 Cepheids in the galaxy M100. From this data determine the distance to M100 and the uncertainty.

Star | Luminosity / W | Brightness / Wm?"
— | — | —
Cepheid 1 | 3.9 x 10"? | 9.3 x 10???
Cepheid 2 | 1.2 x 10"? | 3.8 x 10???
Cepheid 3 | 2.5 x 10"? | 8.7 x 10???

Added by Melissa Z.

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