Answer: 1. Through spectrum
2. Through wavelength
3. Through Doppler effect
Step-by-step explanation:
1 ) Composition : When light passes through celestial objects it gives some pattern on emission and absorption spectrum. As different celestial bodies are made up of different material their spectrum differs from one another thus giving information about their composition.
2) Temperature : The wavelength emitted by each celestial body gives a graph stating the radiation emitted by them. This helps to find the temperature.
3) Motion : Doppler effect very well define the motion of celestial bodies. Wavelengths shifts in this effect and the ratio of wavelengths of shifted to the non shifted lines gives us information about the motion of celestial bodies.