Why would the light and heat from the merging stars not pose a significant thermal threat to Earth?

Answer

The vast majority of light-emitting stars remain millions of light-years away from the solar system

Even at the closest point of passage during the merger, the light-emitting stars from the merging galaxy would still be millions of light-years distant, meaning the change is purely aesthetic and gravitational, not thermal.

Why would the light and heat from the merging stars not pose a significant thermal threat to Earth?

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