Transient astronomy films the universe’s biggest dramas: Best ideas of the century

Go back 1000 years and look at the night sky and you may notice additional points of light compared to today. At the time, Chinese astronomers called these “guest stars” and believed they were harbingers of great change.

We now know that they were probably supernovae – explosions caused by dying stars – and they are one of many happy accidents that occurred when astronomers were looking at the right place at the right time.

But at the turn of this century, the search for these “transient” events became a tactic in its own right, and it is completely changing the way we practice astronomy. Since then, we have discovered a myriad of intermittent events in the cosmos, ranging from nanoseconds to longer than a human lifetime.

“You think of the universe as having a different range of spatial scales, but it also has these ranges of temporal scales, and they are incredibly poorly explored in astronomy,” says Jason Hessels of the University of Amsterdam in the Netherlands.

Relying on chance to capture these events risks missing a lot of the action. That’s why astronomers have now automated the process of serendipity, with surveys like the Palomar Transient Factory, which ran from 2009 to 2012, coordinating telescopes like a well-oiled machine. The main telescope in San Diego, California, would see an interesting flash and another would investigate further. “It was really organized like a conveyor belt,” Hessels says.

Many other telescopes whose aim is to search in time rather than space followed. These include the Zwicky Transient Facility, Palomar’s successor, and the Pan-STARRS survey, which collected the largest volume of astronomical data ever, 1.6 petabytes, from its perch in Hawaii.

These and other telescopes produced a torrent of data that revealed the flickers of the universe: gamma-ray bursts, fast radio bursts, gravitational waves, and stars exploding either on their own or because they were torn apart by black holes.

Ephemeral astronomy is transforming the way we describe the universe. “We started with drawings, then photographs, then something like a stop-motion film,” says Hessels. Now we are getting closer to a full film, he said. “It seems like every time we change the way we look at the sky, we fill more and more of the film.”