Look closely and you’ll see periods, colons, full stops, and even commas. The complicated symbols are a bit tricky to understand, but JWST just found one. There, in spacetime, bent and stretched by gravity, the light from a distant galaxy is shaped like a perfect, giant cosmic question mark.

Its resemblance to a human tongue is, of course, a coincidence (though it’s not the first question mark JWST has detected in deep space), but this particular object’s appearance is due to a property of physics known as perspective, alignment, and gravitational lensing that could help us learn more about the universe.

“We only know of three or four cases of such gravitational lensing configurations in the observable universe,” says astronomer Guillaume Despres of Saint Mary’s University in Canada, “which makes this finding exciting because it demonstrates the power of the Webb and perhaps suggests that we will now find many more of them.”

Spacetime, the fabric of the universe, is not smooth and uniform. Large objects cause it to stretch and deform, like placing a heavy object on a trampoline. Massive galaxies and clusters of galaxies create something similar to spacetime; any light that travels through this spacetime does so in a stretched and distorted way.

For us as observers on Earth to see this distant light, the result is blurring, distortion, multiplication and magnification.

It’s fun to watch, and it also has scientific benefits. It’s a bit like a cosmic magnifying glass, allowing us to see more detail in distant galaxies than we normally can, but scientists often have to manipulate the distorting effects to get useful data.

That’s what we’re looking at here, but it’s a particularly rare type of lens.
hyperbolic core gravitational lensing. An interaction between two galaxies was detected in distant space behind the galaxy cluster MACS-J0417.5-1154. This is what causes the question mark shape.

Because of the way the light from these galaxies bends, five different images of the pair have reached Earth. Four of them form a question mark curve, with the warped bits of light connecting them; the question mark dot is a second, unrelated galaxy hanging out in the right place at the right time.

Astronomers imaged this region with JWST and Hubble and were able to determine that this pair of galaxies, called question marks, are equidistant from us and both emit light that took 7.2 billion years to reach us.

This confirms that galaxies do indeed interact with each other. Both begin to blossom with star formation as gravitational interactions cause star-forming dust clouds to come together, twist, and collapse into baby stars.

“Knowing when, where and how stars form in galaxies is critical to understanding how galaxies have evolved over the history of the universe,” says astronomer Vicente Estrada-Carpenter of Saint Mary’s University.

“Both galaxies in the question mark pair show active star formation in a few dense regions, probably as a result of gas from the two galaxies colliding. However, neither galaxies appear to be very distorted in shape, so we are probably seeing the beginnings of their interactions with each other.”

While gravitational lenses are not surprisingly rare, they vary in quality, and we don’t always get useful information from them. Such an observation, which looks like a pair of question marks, is a rare glimpse not only into the history of the universe, but also into the Milky Way’s own history of strange violence.

“It looks amazing,” says Marcin Savicki, an astronomer at Saint Mary’s University, who said the images were so spectacular that it was part of my interest in astronomy as a child. “These galaxies, seen billions of years ago when star formation was at its peak, are similar in mass to the Milky Way at that time. Webb is allowing us to explore what our own galaxy would have been like in its younger years.”

A survey review in which this observation was published was published at: Monthly Notices of the Royal Astronomical Society.