Calculating relative velocity of Crab Nebula

In summary, the conversation discusses the use of the Doppler formula to calculate the relative velocity of the approaching and receding filaments of the Crab Nebula. The speaker initially uses the formula v=c(Δλ/λnaught) and obtains a result that is significantly different from the actual velocity of the expansion. They then consult a cosmologist who suggests dividing the formula by two, resulting in a much closer approximation of the actual velocity. The reason for this division is that half of the difference between approaching and receding filaments is assigned to the shift from approach and half to the shift from recession.
  • #1
LavaLynne
7
0
I'm using the the Doppler formula to calculate the relative velocity between the approaching and receding filaments of the crab nebula: Δλ/λnaught = v/c Change in wavelength/ wavelength = velocity/ speed of light

I have reworked the formula as v= c(Δλ/λnaught)

When I plug in the values I get: 300,000 km/s (38.336 angstrom/ 3727 angstrom) = 3085.81

As this is nowhere near the velocity of the Crab's expansion I asked a cosmologist friend for help. He said that I should do the formula as: v= c(Δλ/λnaught) / 2

This gives me: 300,000 km/s (38.336 angstrom/ 3727 angstrom) /2 = 1542.90 km/s

Now this result is very close to the actual velocity of the expansion. What I'm wondering is...why am I dividing by two?

Keep in mind that I'm a mature student and this my first year of school in a very long time! Please go easy on me! :)
 
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  • #2
You're looking at the difference between approaching and receding filaments. Half that difference is assigned to the shift resulting from approach, and half to the shift due to recession.
 
  • #3
Thank you very much for that! That make quite a lot of sense! :)
 

1. How is relative velocity calculated for the Crab Nebula?

Relative velocity is calculated by measuring the difference in velocity between the Crab Nebula and a reference point. This can be done using Doppler shift measurements of the nebula's spectral lines or by comparing its position and velocity to other objects in the same region of space.

2. What is the current estimated relative velocity of the Crab Nebula?

The Crab Nebula is currently moving away from Earth at a relative velocity of approximately 1,500 km/s. This is based on observations of its spectral lines and comparisons with other objects in the same region.

3. How does the relative velocity of the Crab Nebula affect its appearance?

The relative velocity of the Crab Nebula has a significant impact on its appearance, as it causes the nebula to appear distorted and elongated due to the Doppler effect. This can be seen in images and observations of the nebula.

4. Can the relative velocity of the Crab Nebula change over time?

Yes, the relative velocity of the Crab Nebula can change over time due to various factors such as gravitational interactions with other objects and the expansion of the universe. However, these changes are relatively small and can only be measured with advanced techniques.

5. How does calculating the relative velocity of the Crab Nebula help us understand the universe?

By calculating the relative velocity of the Crab Nebula, we can gain a better understanding of its motion and the dynamics of the surrounding space. This can provide insights into the formation and evolution of the nebula and its role in the larger structure of the universe. Additionally, it can also help us refine our understanding of fundamental physical laws and theories.

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