Aided by a trick of gravity, astronomers have found a normal galaxy. Big deal, right? The thing is, where they found it is not normal: The light we see from it left the galaxy 12.4 billion years ago, meaning we’re seeing it as it was when the Universe itself was only 1.4 billion years old!
That’s what makes this so weird. A normal galaxy has no business being there when the cosmos was so young. But yet, there it sits.
The galaxy is called SPT–S J041839–4751.9 (let’s call it SPT0418 for short), and was discovered in a sky survey using the South Pole Telescope, which looks at light in the millimeter wavelengths, far outside what our eyes can see. The galaxy was flagged as interesting at the time, since it appeared to be dusty and cranking out new stars.
Follow-up observations were made using ALMA, the Atacama Large Millimeter/submillimeter Array, which is far more powerful and has much keener eyesight, so to speak. What they saw is one of the first weird things about this normal galaxy.
The ALMA image of the very distant galaxy SPT0418, distorted into a ring due to the gravity of an intervening galaxy. Credit: ALMA ...