What is the Speed of Galaxies by Redshift?

In summary, the conversation discussed the calculation of the speed at which galaxies are moving away from us based on their redshifts. The observed wavelengths of the hydrogen emission line for three galaxies were given, along with the rest wavelength of 656.3 nanometers. The galaxies were identified as Galaxy 1, Galaxy 2, and Galaxy 3, with observed wavelengths of 659.2, 664.4, and 683.1 nanometers, respectively. The additional information provided context for the conversation, stating that the galaxies were the results of obtaining spectra and measuring the observed wavelengths.
  • #1
iamthemeg
2
0

Homework Statement


I am trying to calculate, from their redshifts, the speed at which each of the following galaxies is moving away from us. Give your answers in both km/s and as a fraction of the speed of light.

The galaxies are:
Galaxy 1: Observed wavelength of hydrogen line is 659.2 {\rm nanometers}.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 {\rm nanometers}.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 {\rm nanometers}.

Additional Info:
Imagine that you have obtained spectra for several galaxies and have measured the observed wavelength of a hydrogen emission line that has a rest wavelength of 656.3 nanometers. The above galaxies are the results.
 
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  • #2
oops, that should read,
"Galaxy 1: Observed wavelength of hydrogen line is 659.2 nanometers.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 nanometers.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 nanometers. "
 

1. What is redshift and how does it relate to the speed of galaxies?

Redshift is a phenomenon in which the light emitted from an object appears to be shifted towards longer wavelengths, meaning the light has a lower frequency. This is often observed in galaxies and is caused by the expansion of the universe. The speed of galaxies is related to redshift because the faster a galaxy is moving away from us, the greater the redshift will be.

2. How is the speed of galaxies calculated using redshift?

The speed of galaxies can be calculated using Hubble's Law, which states that the recessional velocity of a galaxy is directly proportional to its distance from us. This law takes into account the redshift of the galaxy and uses it to determine its speed. Other methods, such as spectroscopic observations, can also be used to measure the speed of galaxies.

3. Can redshift be used to measure the speed of galaxies accurately?

While redshift can provide a good estimate of the speed of galaxies, it is not always accurate. This is because redshift can also be affected by other factors such as the gravitational pull of nearby objects or the galaxy's own motion. Therefore, multiple methods are often used to determine the speed of galaxies and to account for any potential inaccuracies.

4. What is the significance of studying the speed of galaxies by redshift?

Studying the speed of galaxies by redshift is important in understanding the expansion of the universe and the overall structure and development of galaxies. It can also provide insights into the distribution of matter in the universe and the effects of dark matter. Additionally, studying redshift can help us determine the age of the universe and make predictions about its future.

5. How does the speed of galaxies by redshift support the Big Bang Theory?

The Big Bang Theory states that the universe is expanding, and the speed of galaxies by redshift provides evidence for this. As galaxies move away from each other, the light they emit is shifted towards longer wavelengths, resulting in redshift. This supports the idea that the universe is expanding and provides a way to measure the rate of expansion.

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