A Movie 130 Million Years in the Making

The spectacular neutron-star collision eventually faded from view, but it was immortalized by space animators.

Artist’s impression of neutron stars about to collide
Artist’s impression of neutron stars about to collide (ESO / L. Calçada / M. Kornmesser)

It took 130 million years for astronomers to see the light. On August 17, scientists observed through telescopes a small, glowing orb, the remnants of a collision between two neutron stars in another galaxy that triggered universe-bending gravitational waves. They watched as the sphere changed from royal blue to crimson red, as lighter chemical elements in the cloud of radioactive debris gave way to heavier ones, like gold, platinum, and silver. About a week later, it faded.

The light show may be over in the night sky, but it can be found on the internet and replayed, over and over, as a dreamy short video:

Luís Calçada created the video for the European Southern Observatory, whose fleet of telescopes in Chile tracked the aftermath of the collision. Calçada is a member of ESO’s education and public-outreach department, a team of astronomers and science-communication specialists in Munich.

“We wanted to have something striking, but we wanted it to be correct,” Calçada said.

The clip is another addition to a rapidly growing volume of illustrations and animations of wondrous astronomical objects and phenomena. As the rate of discovery of exoplanets has picked up in the last several years, so has the production of visualizations of these worlds. Often, scientists and illustrators have only a few pieces of the puzzle, like the mass, temperature, and orbit. They look carefully at how these factors have shaped the celestial bodies that we can see, and use it as inspiration to create a full picture of those we can’t. When astronomers discovered the presence of seven Earth-sized planets in a star system 39 light-years away, illustrators turned tiny blips in data into colorful alien worlds.

Calçada has worked at ESO for about 11 years. He was studying astronomy in school when he started experimenting with computer graphics. He eventually decided that he wasn’t going to be a scientist, and he went into science communication instead. The ESO gig, he said, is the perfect mix.

When exciting research papers come in at ESO, it’s up to Calçada and the rest of the team to create compelling visuals out of the data. They come up with designs for illustrations and videos, send it to the paper authors for feedback, and exchange notes until everyone’s happy with the product. When scientists have few specifics, the animators have some creative freedom. “But of course, some other times, they say no, that wouldn’t happen because the star is too big or the temperature is too high,” Calçada said.

On some rare occasions, illustrators get to check their designs against the real thing—they just have to wait for technology to catch up with them. In 2009, astronomers using ESO’s Very Large Telescope published some research about Pluto’s thin atmosphere, which is mostly nitrogen with some methane. Calçada whipped up a short video to accompany the research. The clip, “filmed” from the perspective of a camera panning over the surface of the dwarf planet, showed a hazy, bluish atmosphere over gray, Arctic-esque terrain. When the New Horizons spacecraft arrived at Pluto in 2015, it returned images of the dwarf plant that looked eerily similar.

Illustrations and animations of scientific research make the cosmos look like a radiant place bursting with color. But it’s worth remembering that the universe doesn’t always look that way to the scientists doing the work, Calçada notes. “They’re usually looking at boring code on the computer,” he said.

Many astronomers rely on spectroscopy, a technique that involves measuring the light across the entire spectrum of electromagnetic radiation. Astronomers use spectroscopic instruments in telescopes to observe different wavelengths coming from an object, from radio waves to visible light to gamma rays. The data, known as spectra, appears to astronomers as a simple squiggly line on a plot, like a cosmic electrocardiogram. But the spikes and dips can reveal a lot about the object in question, whether it’s a single star or an entire galaxy, like its mass, temperature, and chemical composition. In other fields of scientific study, Calçada said, “you can go outside, you can study the rocks, you can study the plants, you can look at the fossils. But astronomers, they only have light.”

Light was exactly what astronomers wanted to find in this kind of discovery. Before this week, scientists had detected gravitational waves four times, but the ripples came from collisions of black holes, which don’t emit any light. Astronomers had no way of knowing where exactly the waves originated. The new finding marks the first time we have seen the source.

Space illustrations sounds like they should evoke wonder at all times, but for the people making them, they can seem pretty routine. Calçada said his first few exoplanet projects were exciting, but as more and more were discovered, the work of animating them began to feel a little mundane. Oh, look! Another rocky planet. Eventually, perhaps soon, the work of visualizing cosmic collisions might lose some of its thrill, too; the scientists running the gravitational-wave detectors predict the extremely sensitive instruments will detect one or more mergers a week.

“But don’t worry, there’s going to be more exciting astrophysics and astronomy,” Calçada said. “There’s always going to be something more exciting and new coming out. I’m not worried of getting bored.”