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Can superheavy elements (such as Z=116 or 118) be formed in a supernova? Can we observe them?

It is theorized that an island of nuclear stability exists in the 114-116 region of atomic mass. (Note by Sara: I think you mean atomic number.) I assume that even though we can't find such elements in our neighborhood, they may be produced in the supernova of a sufficiently large star.

My questions are as follows:

1. Does a theoretical formulation exist which can predict the isotope yields of elements for the supernova of a given stellar mass?

The elements with atomic numbers greater than that of iron are made in a variety of processes, notably s-process (s for slow) and r-process (r for rapid) neutron capture. The way it works is this: you start out with a seed atom, say (56,26)Fe. You're in a region of high neutron flux (e.g. a supernova), so neutrons start to pile up on your atom. After you collect 6 neutrons, your atom becomes (62,26)Fe, which is unstable to beta decay on a time scale (about 1 minute, in this case) shorter than the time between neutron captures. Before it can collect any more neutrons, it beta decays to (62,27)Co, which beta decays to (62,28)Ni, which is stable. Now neutrons start to collect on the Ni, and so it goes, stepping through the periodic table. When the atomic number or mass number gets too high, however, neutron capture induces fission. Whether the island of stability can be reached therefore depends on the maximum atomic number that can support the r-process described above without induced fission occuring. Once the island of stability was predicted, people started writing lots of papers saying both yes, no and maybe to the question of whether the island of stability could be reached by the r-process. The field settled at a solid "maybe" before it petered out. So, in answer to your question, no--people have yet to determine whether the stable superheavy elements are formed at all. It's a matter of the nature of the universe, rather than one finding a star that's massive enough. (Of course, the scenario I described is not the only possibility--it is possible that a binary system of a neutron star and a black hole would be a good place to form super-heavies, but I still have 3 questions left to answer so I'd better not get into that! At any rate, no one has really made a granite case that it's possible anywhere {except for a man-made accelerator}, so it's "maybe"'s across the board.)

2. If so, can a prediction be made of the likelihood of finding stable super-heavy elements (114-116) in the universe? Has that already been done?

The lifetimes have been painstakingly predicted, but as the answer to #1 pointed out it, has yet to be proven whether these guys are formed at all, much less at what rates. Without that, you can't tell.

3. Do we know what to look for? (can we predict the spectral properties of these postulated isotopes)

Actually, predicting the chemistry of the superheavy elements is a whole neat field of its own--it turns out that when the atomic number is as high as that, you need some pretty fancy quantum mechanics to get it right. And if you then observe the element, you can see whether your fancy quantum mechanics got it right, or if it might need to be revised. People have done their best to predict everything down to the shoe sizes of these elements.

4. If so, is anyone looking?

Absolutely--and search actually does takes place within the bounds of the solar system. The material that makes up the solar system has already been through the stellar life cycle, so if superheavy elements were produced in supernovae, they could be found in our neighborhood (so many "super"'s--scientists can really lack originality sometimes). Rather than trying to detect radiation from the superheavies (which is unlikely), people have checked meteorites for evidence of cosmic rays made of superheavy elements and searched in samples from Earth and its moon, with no conclusive results.

As a final note, I should point out that there has been a lot of success sythesizing these elements--they've made Z=110, 112, 114, and 116, and the 1/2-life of one of their isotopes of 114 was about 30 sec. (You may have heard about the big scandal involving Z=116 and 118 a few years back, but another group did actually make 116 after that. As far as I know, no one's gotten 118 yet.)

January 2004, Sara Slater (more by Sara Slater) (Like this Answer)

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