Two galaxies. Opposite spins.
They met. The rotation canceled.
XMM-VID1-2075 formed less than 2 billion years after the Big Bang. It already held several times more stars than the Milky Way. It had already stopped forming new stars. And it was not spinning.
Galaxies rotate. They inherit angular momentum from the collapse that formed them. A galaxy this young should still be spinning furiously. Slow rotators — galaxies whose coherent spin has been scrambled — are old things, worn down by billions of years of mergers. This one looked that old at two billion years.
The most likely explanation: two galaxies that happened to be spinning in nearly opposite directions, colliding. The angular momenta didn't add. They subtracted. Two real rotations. Summing to nothing.
The stars are still there. The mass is still there. Only the motion was erased — by having met something equal and opposite at exactly the wrong moment.
This is not absence. It is cancellation. The difference matters.