It is not a small rock, but the remains of a remarkable supernova

A rock discovered in Egypt in 1996 seems to be from a thermonuclear supernova that occurred light years away from us, a few billion years ago. How do scientists trace the deadly history of this rock?

It weighs 33 grams and is called Hypatia. It’s a rock. But it’s different from what you usually get, because it’s from far away. Discovered in 1996 in Egypt, Hypatia is an extraterrestrial rock (literally). It probably came from the nucleus of a comet. Because of this specificity, it has been studied extensively.

A study, to be published in August 2022 in the scientific journal Icarus (but already), suggests that Hypatia is even more interesting: it is the remnant of a supernova, and, moreover, of a unique kind that we have no material tracking of Earth’s time. How do we trace the potential interstellar history of a rock?

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

Here is the (potential) history of Hypatia

The chemical composition of anything tells a story. It reveals a chronology and an origin. Hypatia suggests that it is from dust and especially characteristic gases: it is from a “parent” object that forms itself from a type Ia supernova, meaning thermonuclear. The shape of the stone, that is, the way in which all the material is assembled, is an additional indication.

In a way, we can say that we were surprised to see a supernova Ia explode in full action, because the gas atoms from this explosion were caught in the surrounding dust cloud, which eventually became the parent body. of Hypatia. “, Details of one of the authors, Jan Kramers, on the site of the University of Johannesburg on May 17.

Dating is just as confusing, because it means that the rock was formed billions of years ago, when our solar system was just born (about 4 billion years ago).

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

To reach this conclusion, the scientists performed a chemical analysis by targeting 17 areas in a very small sample of Hypatia. The result showed low levels of silicon, chromium and manganese. This initial observation ensures that the rock is not from the solar system. Then, the analysis shows that, on the other hand, there are high levels of iron, sulfur, phosphorus, copper and vanadium: this second observation shows that the matter is not from the spatial environment, nor even in our Milky Way arm. Paagi.

The composition also commands a red giant star as the source. Similarly, chemical analysis showed that Hypatia has a very high rate of iron compared to silicon and calcium, excluding the origin of a type Ib supernova (known as “ of the heart broken “).

By continuing this approach through successive releases, only one possibility remains, and the most interesting of all: the thermonuclear supernova Ia. These supernovae from binary stars are rare, but it is believed that any resulting rock must contain some chemical elements in unusual proportions. However, precisely, all of Hypatia’s analyzes make it possible to “match” the rock to what is expected of a thermonuclear supernova.

Well almost. Scientists have also identified chemical elements (such as phosphorus or potassium) that seem incompatible with this type of supernova. However, this cannot be described: these elements can be derived from various events occurring in the region, before or during the supernova. In summary, at this stage of research, we can consider Hypatia as the most likely trace material – to be found on Earth – in a supernova Ia. And that’s no longer bad as evidence, because we’re talking about a huge explosion that happened billions of years ago, a few light years away.

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