This is not a rock, but a 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 billions of years ago. How have scientists traced the dizzying history of this stone?

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

A study that will be published in August 2022 in the scientific journal Icarus (but already available), suggests that Hypatia is even more fascinating: it would be a remnant of a supernova, and in addition of a rare type, of which we had no material trace at the moment on Earth. How can we trace the potential interstellar history of a pebble?

Fragments of Hypatia (with a coin at the bottom). // Source: University of Johannesburg

Here is Hypatia’s (potential) story

The chemical composition of any object tells a story. It reveals a chronology and an origin. That from Hypatia suggests that it comes from dust and particularly characteristic gases: it would come from a “parent” object, which itself would have formed from a type of Ia supernova, that is, thermonuclear. The shape of the rock, that is, the way in which all this material has accumulated, constitutes 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 this explosion were trapped in the surrounding dust cloud, which eventually formed Hypatia’s parent body “, Describes one of the authors, Jan Kramers, on the website of the University of Johannesburg on 17 May.

The dating is just as dizzying as it would mean that the rock was formed over the last billion years when our solar system was just born (about 4 billion years ago).

Thermonuclear supernova or not: what is the level of safety?

To reach this conclusion, the researchers performed a chemical analysis by targeting 17 areas of a very small sample of Hypatia. The result showed that there were low levels of silicon, chromium and manganese. This first observation ensures that the stone does not come from the solar system. Then the analysis showed that on the other hand there were high levels of iron, sulfur, phosphorus, copper and vanadium: this second observation shows that the object does not come from the spatial proximity, nor from our arm of Milkstone. Way.

The composition also excludes a red giant star as a source. Similarly, the chemical analysis shows that Hypatia contains too much iron compared to silicon and calcium, which precludes the origin of a type Ib supernova (known as ” in the heart collapse “).

Continuing this way by successive exclusions, there was only one option left, and the most exciting of all: the thermonuclear supernova Ia. These supernovae from binary stars are rare, but it is speculated that any resulting rock must contain certain chemical elements in unusual proportions. But precisely all the analyzes of Hypatia make it possible to “match” the stone with what is expected of a thermonuclear supernova.

Well almost. Scientists have also identified chemical elements (such as phosphorus or potassium) that do not appear to be compatible with this type of supernova. However, this is not inexplicable: These elements may have originated 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 as the most likely material trace – found on Earth – of a supernova Ia. And that’s already not bad as evidence, as we’re talking about a giant explosion that took place billions of years ago, several light years away.

Look at the world from space

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