To determine how Star A and Star B are moving relative to each other based on the observed absorption lines of Oxygen, we can use the concept of the Doppler effect.
The Doppler effect states that the observed wavelength of a wave (in this case, light) is shifted as a result of the relative motion between the source of the wave and the observer. If an object is moving toward the observer, the observed wavelength appears shorter (blue-shifted), and if an object is moving away from the observer, the observed wavelength appears longer (red-shifted).
In this case, since Star A's absorption line of Oxygen appears at a longer wavelength (504 nm) compared to the lab value (500 nm), it indicates that the line is red-shifted. This implies that Star A is moving away from the observer.
Similarly, Star B's absorption line of Oxygen appears at a longer wavelength (508 nm) compared to the lab value (500 nm), suggesting that the line is also red-shifted. Therefore, Star B is also moving away from the observer.
In conclusion, both Star A and Star B are moving away from the observer, but the shift is greater in Star B as its absorption line is at a longer wavelength (508 nm) compared to Star A's absorption line (504 nm).
We observe an absorption line of Oxygen at 504 nm in Star A and at 508 nm in Star B. We know in the lab
this line has a wavelength of 500 nm. How are Star A and Star B moving relative to each other?
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