Question

When a galaxy is observed moving toward the earth, what visible radiation (as in, which color) will it emit?

Answer 1

It will emit Red because it is moving towards (which creates heat) instead of away (which is blue and cooler).

I hope this helps!

Answer 2

When a galaxy moves towards the earth, it will emit blue colour light.

Doppler blueshift occurs when the source of light is coming near to its observer. Alternatively, Doppler redshift occurs when the emitter of light moves away from its observer.

Blueshift occurs when wavelength of light decreases. Redshift occurs when wavelength of light increases.

Blueshift makes the colour of the light move from red towards blue.

The shift in wavelength is determined by observing the spectrum with a spectrometer.