Can someone please explain to me how they know that celestial bodies have light or heavy elements? What types of instruments do they use or is it a calculated math equation on a white board. I've never understood it.
I get the doppler affect that shows movement. I get the infra-red spectrum of light. I don't get this. Help.
I’m sure there is an equation to determine the mass based on it’s speed and distance from the host star...............