Heat detector finds explosive stars in cosmic game of “I Spy”


This exploding star, known as the “Firework Nova” is an example of the types of stellar explosions that can be examined by repurposing radio telescopes. Image: NASA

By Kate Townley

A new way of exploring the universe has been under our noses for years.

Scientists are only now discovering this by looking at the sky from a different perspective. A recent study shows how we can use existing technology to better understand distant objects with strange, previously unseen behavior.

It’s a two-for-one: technology that detects heat in the sky can also find supernovae and other cosmic explosions.

“There are many explosive events occurring in the cosmos,” said Brian Metzger, an astrophysical theorist at Columbia University, who contributed to the paper published in the Astrophysical Journal. “These events appear bright but then fade away quickly.”

These blasts of material from star collisions and explosions happen so fast that they are hard to study, he said. That makes them a mystery to astronomers. The behavior of these objects – called transients – is largely unknown. They last only days to weeks. That makes them hard to find. Telescopes would need to look at the whole sky constantly to observe more transients, Metzger said.

Think of finding transients like a kid looking through an “I Spy” book. Radio telescope surveys search the sky, sorting through stars, galaxies, dust, planets, and other celestial objects. All of this is to find one specific type of object.

But scanning the sky isn’t as easy as finding a marble on a page of random objects. Instead, it’s akin to being put into a library of “I Spy” books and told to find one object, in one specific book, on one specific page. The only problem? You aren’t told where it is.

The sky is huge, and according to Nathan Whitehorn, a Michigan State University astrophysicist, it’s crucial to know what you’re looking for and where you can find it.

The good news is that we already have technology that examines the whole sky – it’s just being used for something else. Cosmic Microwave Background surveys use telescopes and other scientific instruments to scan the sky for heat. They usually focus on leftover heat from the Big Bang, the explosion theorized to bring the whole universe into existence in one quick burst. But if scientists know where to look, they can use this technology to uncover more transient data.

“One of the things we realized a few years ago was that [these] telescopes can detect more [than just] cosmic microwave background,” explained Whitehorn.

This is where the study comes in. Astronomers took what little data there is about these mystery explosions and created a simulation. Through their results, they were able to predict where transients might be, how long they’ll last and how many we can expect to find.

Technology used for observing heat distribution from the Big Bang can be repurposed to find distant exploding stars. Image: NASA

Until now, these surveys haven’t been used for finding transients, Whitehorn said. The information from the study gives an idea of what transient data the surveys could gather if they looked at more than just the distributed heat leftover from the Big Bang.

“Although these surveys are designed for cosmic microwave background science, we can use them to get this transient science return for free,” the paper’s first author, Tarraneh Eftekhari, wrote in an email.

Eftekhari, a radio astronomer at Northwestern University, emphasized that using these surveys can give unexpected free data. As surveys monitor large parts of the sky at a time, they are more likely to observe short-lived events. And based on the simulation run by Eftekhari and her team, there will be many events to observe.

Using Cosmic Microwave Background surveys in a different way helps us understand a part of the universe we don’t know much about, Metzger said.

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