The bright infrared light emanating from two galaxies in the process of merging has just come out of hiding. Using the JWST, astronomers have located the light behind a thick wall of dust that blocks it at other wavelengths. What emits the light is still unknown, but narrowing its position will help us understand what it is and why it shines so much more than expected.

“The James Webb Space Telescope has given us completely new images of the universe with the highest spatial resolution and sensitivity in the infrared,” says astrophysicist Hanae Inami of the Hiroshima Astrophysical Science Center at Hiroshima University in Japan.

“We wanted to find the ‘engine’ powering this merging galaxy system. We knew this source was deeply hidden by cosmic dust, so we couldn’t use visible or ultraviolet light to find it. Only in the mid-infrared, as seen from the James Webb Space Telescope, this source is located in these merging galaxies. Do we see now that it outshines everything else?

While the universe is mostly empty space, galaxy mergers are not uncommon. Large galaxies are brought together by the relentless force of gravity to form larger galaxies.

It’s not even just something distant happening to other galaxies elsewhere: The Milky Way itself is a cosmic Frankenstein monster made up of a fraction of every other galaxy it devoured during its billions of years of life.

Many examples of galaxy mergers have been found at various stages in the wider universe, but this is a slow process that can take millions to billions of years.

Scientists need to take samples and reconstruct the timeline as a single frame from a movie, and other samples are single frames from similar but different movies. It’s painstaking work, but it’s one of the best tools we have for understanding galaxy mergers.

From the light emitted by these mergers, we know that they are quite alive. Although galaxies are mostly space, stars can collide with each other or interact gravitationally, disrupting each other’s orbits.

Clouds of star-forming gas between stars can also collide with each other, creating shocks that can trigger crazy waves of star formation known as starbursts, visible as infrared light shining from dust clouds.

This is what scientists expected to see in 2010 when they pointed the Spitzer Infrared Space Telescope at a galaxy merger called IIZw096 500 million light-years away.

Instead, they detected a bright infrared light shining at the center of the ongoing collision. Unfortunately, Spitzer did not offer high enough resolution to pinpoint the light source, and the mystery had to be shelved.