Galaxies Without Dark Matter: Not a Mirage After All ✦
A billiard ball, crashing into a pyramid, scatters the balls into a fanciful chain. Something similar likely happened in space: a collision between two clumps of dark matter squeezed ordinary matter into a line of dwarf galaxies, nearly devoid of an invisible framework. Back in the last century, Vera Rubin and Fritz Zwicky showed that normally this unseen mass holds stars together, and Edwin Hubble emphasized: without precise distances, we can't decide whether we're seeing reality or an illusion.
Telescopes "James Webb" and "Hubble" measured distances to each dwarf via subtle pulsations of light, while also using photometry to account for distortions from cosmic dust and spectroscopy to determine their speeds.
As it turned out, all eight dwarfs hang out in the same region, 65 million light-years away. The illusion is dispelled. Though, famously, galaxy DF2 crept a little closer—55 million light-years—and that's a new puzzle. But the main point is indisputable: galaxies without dark matter exist, and perhaps they will tell us what the invisible framework of the Universe is made of.
🎯 Galaxy DF2 was first spotted way back in 1978, but its astonishing property—almost total absence of dark matter—was only realized 40 years later.