Seeing that picture of a star absorbing another, I got a dumb question: Stars are balls of glowing plasma. If you were to vacuum it, as another star or black hole too close for comfort would, what would this plasma look like? I reckon it would not be visible, a bit like trying to vacuum fire. All you get is hot, invisible gas. So effectively, the image at the top of the article is completely unrealistic. Any transfer…
Hot things emit light. The wavelength(s) of light a substance emits depends on the temperature of that substance - cooler things emit longer (redder) wavelengths, hotter things are bluer. If the substance is cool enough, the light emitted will be mostly or wholly infra-red, therefore invisible to the naked eye but still detectable. The top of a flame is like that - the gas is still hot but no longer glowing visibly as it cools. Therefore the answer to your question depends on how hot the plasma is, but a confounding factor is that the hoovering object would create friction in the incoming material, thereby heating it up. I think the corona of a star glows with its own light (not just light emitted by the core), so I expect therefore that you would see a lot of light overall, especially nearer to whatever is doing the vacuuming.