At first, they were mistaken for rare 'furnace' galaxies, where a black hole runs at full throttle, heating dust until it glows. Both types show a V-shaped dip in their spectrum — dust muffles some colors while letting others through. But precise brightness measurements revealed a difference. In the 'furnaces,' the dust is so hot that radiation spills deep into the red and bursts out as X-rays. In the red dots, the dust is cooler, and there's almost no X-rays.
It seems their 'engines' never experienced violent flares after galaxy collisions and grew gradually. This hunch changes the picture of how galaxies matured after the Big Bang.
The first Webb images were so thick with these dots that astronomers jokingly called them 'polluters' of galactic surveys.