in astronomy, what does it mean to cross correlate stellar spectra to get a radial velocity.
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Imagine you have two songs, one playing on a speaker and another one recorded by a microphone. When you cross-correlate these songs, you’re essentially comparing them to find out how much the recorded song is shifted in time compared to the original one.
In astronomy, when you cross-correlate spectra, you’re comparing the spectrum of light from a star with a reference spectrum. By doing this, you’re looking for shifts in the wavelengths of light. These shifts can be caused by the star moving towards or away from us, which is known as radial velocity.
So, cross-correlating spectra helps astronomers measure how fast a star is moving along our line of sight, which is its radial velocity. It’s like figuring out if a car is moving closer or farther away from you by comparing the sounds it makes at different times.
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