This isn’t a pebble, it’s the remnant of a rare supernova

A rock discovered in Egypt in 1996 appears to have come from a thermonuclear supernova that took place light-years away from us several billion years ago. How have scientists traced the dizzying history of this stone?

It weighs 33 grams and is called Hypatia. It’s a stone. But it’s quite different from the ones you can usually pick up because it comes from far away. Discovered in Egypt in 1996, Hypatia is (literally) an alien stone. It most likely came from the nucleus of a comet. Because of this peculiarity, it is thoroughly studied.

A study to be published in the journal in August 2022 Icarus (but already available) suggests that Hypatia is even more intriguing: it would be a supernova remnant, and also of a rare type that we had no physical traces of on Earth at the moment. How can we trace the possible interstellar history of a pebble?

Fragments of Hypatia (with a coin below). // Source: University of Johannesburg

Here’s the (potential) story of Hypatia

The chemical composition of an object tells a story. It reveals a chronology and a provenance. Hypatia’s suggests that it came from dust and particularly distinctive gases: it would have come from a ‘parent’ object that would have formed itself from a Type Ia supernova, i.e. thermonuclear. The shape of the rock, in other words the way all this material was assembled, is an additional clue.

In a way, we can say that we surprised the explosion of a supernova Ia in full action because the gas atoms from that explosion got trapped in the surrounding dust cloud that eventually formed Hypatia’s parent body ”, details one of the authors, Jan Kramers, on the University of Johannesburg website on May 17.

The dating is just as staggering as it would mean the stone was formed in the last billion years, when our solar system was just being formed (around 4 billion years ago).

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To reach this conclusion, the scientists performed a chemical analysis by targeting 17 areas of a very small sample of Hypatia. The result showed that low levels of silicon, chromium and manganese were present. This first observation ensures that the stone is not from the solar system. Analysis then showed that iron, sulphur, phosphorus, copper and vanadium were high: This second observation shows that the object is not from spatial proximity, not even from our arm of the Milky Way.

The composition also rules out a red giant star as a source. Similarly, chemical analysis shows that Hypatia contains too much iron compared to silicon and calcium, suggesting the origin of a Type Ib supernova (known as ” in heart failure “).

By proceeding through successive exclusions in this manner, only one possibility remained, and the most intriguing of all: thermonuclear supernova Ia. These binary star supernovae are rare, but it is speculated that any resulting rock must contain certain chemical elements in unusual proportions. In fact, however, all analyzes of Hypatia make it possible to “match” the stone with what is expected of a thermonuclear supernova.

Almost. Scientists have also identified chemical elements (like phosphorus or potassium) that appear to be incompatible with this type of supernova. However, this is not inexplicable: these elements can be inferred from various events that took place in the region before or during the supernova. In summary, at this stage of research we can consider Hypatia to be the most likely physical trace of a Supernova Ia found on Earth. And that’s not bad evidence, since we’re talking about a gigantic explosion that took place billions of years ago, several light years away.

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