Velocity of a star for Doppler Spectroscopy

In summary, the conversation discusses solving for Jupiter's effect on the sun's orbital velocity using the formula v = SQR (Gm*/r) and inputting values for G, M, and r. The calculated value for Gm/r is 1.7*10^8, resulting in a square root value of 13044. However, the correct value for Jupiter's orbital speed is 13.07 km/s, not 13070 m/s. This was clarified through a reference to a NASA factsheet.
  • #1
skydivephil
474
9
Im trying to solve back for Jupiters effect on the suns orbital velocity. I've looked up the asnwer and its 12.7 m/s
and the formula I have for this is
http://en.wikipedia.org/wiki/Doppler_spectroscopy

v = SQR (Gm*/r)
where G is Grav constant
M is the mass of the star (planets mass is negligible )
r is the diatcen of the Jupiter sun distance
I have g as 6.673*10^-11
I have the suns mass as 1.989*10^30
I have r as 7.8*10^11
This gives me Gm as 1.32*10^20
so Gm/r = 1.7*10^8
and the square rot of that is 13044. so why did I get 13044 and not the value of 12.7?

Can anyone help?
 
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  • #3

Related to Velocity of a star for Doppler Spectroscopy

1. What is Doppler spectroscopy?

Doppler spectroscopy is a method used to measure the velocity of objects in space, such as stars, by analyzing the shift in their spectral lines. This shift, known as the Doppler shift, is caused by the motion of the object towards or away from the observer.

2. How does Doppler spectroscopy work?

In Doppler spectroscopy, light from a star is split into its component colors by a spectrometer. The resulting spectrum contains dark lines, called absorption lines, which correspond to specific elements in the star's atmosphere. By measuring the shift in these lines compared to their expected positions, the velocity of the star can be calculated.

3. What is the significance of the velocity of a star for Doppler spectroscopy?

The velocity of a star is a crucial factor in understanding its properties and behavior. Doppler spectroscopy allows scientists to measure the radial velocity of a star, which is its velocity along the observer's line of sight. This information can reveal details about the star's orbit, presence of planets, and other physical characteristics.

4. How is the velocity of a star calculated using Doppler spectroscopy?

The velocity of a star is calculated by measuring the shift in the spectral lines and using the Doppler formula, which relates the wavelength shift to the velocity of the star. This calculation takes into account the speed of light and the known rest wavelength of the spectral line being measured.

5. What types of stars can be studied using Doppler spectroscopy?

Doppler spectroscopy can be used to study a wide range of stars, from hot, massive stars to cool, low-mass stars. However, it is most commonly used to study stars with spectral types A, F, G, K, and M, as these stars have prominent absorption lines that are easier to measure. Doppler spectroscopy can also be applied to binary star systems, where the motion of one star affects the spectral lines of the other.

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