Supernova Could Have Left Radioactive Dust In Antarctic Ice

Supernova Could Have Left Radioactive Dust In Antarctic Ice
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Scientists found evidence of dust produced in nearby supernovae hiding under a 500kg of Antarctic snow, according to new research.

Our solar system is more than just the Sun, planets, moons and asteroids — it’s full of dust, much of which might originate from interstellar sources. A team of scientists in Australia, Germany and Austria hopes to find the elemental signature of this dust here on Earth in order to better understand the environment through which the solar system is moving.

“I’m excited about the possibility to learn something about the extreme stellar explosions and large structures around our planet which are unimaginably far away and large,” Dominik Koll, the study’s first author and PhD candidate from The Australian National University, told Gizmodo in an email. This is possible, he says, just by looking at our own planet.

The researchers organised a transport of 500kg of relatively fresh snow (no older than 20 years) from the Kohnen Station in Antarctica to Munich, Germany, melted it in the lab, passed it through a filter, and evaporated it to collect dust and micrometeorites. They incinerated the dust, then put it into an Accelerator Mass Spectrometer.

This method creates charged ions out of the sample, and passes the ions through a magnet and into a particle accelerator before sending it into the detector. It allows the researchers to look for only specific atomic isotopes.

Specifically, the team hoped to find iron-60, a long-lived radioactive isotope released by exploding stars, or supernovae. But the iron-60 might have come from other sources, such as matter irradiated by cosmic rays.

In order to ensure that they were truly measuring interstellar dust, they also searched the sample for manganese-53, another isotope produced by high-energy cosmic rays, and compared their ratio of iron-60 and manganese-53 to the ratio they’d expect if there was no interstellar dust.

They measured way more iron-60 than they’d expect from cosmic rays alone, according to the paper published in Physical Review Letters.

How did the dust get there? Well, this team of researchers has previously shown that a nearby supernova deposited iron-60 in the solar system in the past 1.5 million to 3 million years, explained the study author Thomas Faestermann from TU Munich. If this iron-60-rich dust is still raining down onto Earth, then we could be passing through a dust cloud left over from this supernova.

Studies such as these can better paint a picture of the interstellar environment through which the Sun is travelling. Astronomers have gathered that the Sun is in the midst of a “Local Bubble”, an area where the interstellar medium is much less dense than average, perhaps because of a relatively recent supernova.

Inside the bubble is the Local Interstellar Cloud, a region that’s a little denser than the Bubble. Radioactive nuclei from Antarctic snow could be an important way to probe the origins of the Bubble and Cloud.

There’s plenty more work — Koll hopes to one day explore older material to see how the deposition of this dust changed over time.

But Antarctica is more than just an icy desert. It could be concealing a secret history of ancient supernovae.