# How can I calculate red shift for intragalactic bodies

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• Frank Einstein
In summary, the conversation discusses the use of equations and methods to calculate the red shift of Be stars within the Milky Way. The speaker is unsure if they are using a legitimate method and is concerned about the local motion of the Milky Way affecting their calculations. Another participant confirms that the Hubble flow cannot be used and suggests considering the local motion of the stars.

#### Frank Einstein

Hello everyone. I am doing an studi on Be stars, all of which are inside the Milky Way, I want to show that the red shift won't be a big deal here, but I am confused about how to prove it; what I have done is combining the equations
λr=λe(1+z) and cz=Hd to get λr=λe(1+Hd/c) where z=v/c.

I get extremely minor changes in my red shift if I introduce the Galaxy's diametre in d, but I am not sure that aplying the equation cz=Hd is legitimate here or if it can only be used to measure distances between galaxies.

Can someone please tell me if I am using a good methode to calculate the red shift?

The milky way doesn't follow the Hubble flow, you cannot use the overall expansion of the universe here. You might have to consider the local motion, however, which is of the order of 20-200 km/s (depending on where the stars are in the galactic disk), with some stars moving at up to 1000 km/s.

Frank Einstein
I was afraid that would be the anwser. Thank you very much for telling me.

## What is red shift and why is it important in studying intragalactic bodies?

Red shift is a phenomenon in which the light from a distant object appears to have longer wavelengths, making it appear more red. This is due to the Doppler effect, where the object is moving away from the observer. In studying intragalactic bodies, red shift is important because it provides information about the object's velocity and distance, which can help us understand the expansion of the universe and the structure of galaxies.

## How is red shift calculated for intragalactic bodies?

Red shift is calculated using the equation z = Δλ / λ, where z is the red shift value, Δλ is the difference in wavelength between the emitted light and the observed light, and λ is the emitted wavelength. This equation takes into account the Doppler effect and can be used to calculate the change in velocity of an object.

## What factors can affect the accuracy of red shift calculations for intragalactic bodies?

There are several factors that can affect the accuracy of red shift calculations, including instrumental errors, calibration errors, and gravitational lensing. Instrumental errors can occur due to limitations in equipment such as telescopes and spectrographs, while calibration errors can arise from discrepancies in the calibration of instruments. Gravitational lensing, where light is bent by a massive object in between the source and observer, can also cause inaccuracies in red shift calculations.

## How does red shift differ for intragalactic bodies compared to extragalactic bodies?

The red shift of intragalactic bodies is typically smaller than that of extragalactic bodies. This is because intragalactic bodies are relatively close to us and are not affected by the expansion of the universe as much as extragalactic bodies. Additionally, intragalactic bodies are primarily moving within their own local group, whereas extragalactic bodies are moving due to the expansion of the universe.

## Can red shift be used to determine the age of intragalactic bodies?

No, red shift cannot be used to determine the age of intragalactic bodies. This is because red shift only provides information about the velocity and distance of an object, not the age. To determine the age of an object, other methods such as radiometric dating must be used.