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Dustin DeWinn
2015-Aug-18, 04:13 AM
Hello,

I have heard mixed reports of the element Californium (98) being observed in supernovae.

Independent of this claim, is it at all physically possible for transuranic elements like Californium, element 117, etc to exist even for a fraction of a fraction of a second in cosmic events? Or are these elements only possible in a lab?

Thank you

antoniseb
2015-Aug-18, 12:54 PM
Hello,

I have heard mixed reports of the element Californium (98) being observed in supernovae.

Independent of this claim, is it at all physically possible for transuranic elements like Californium, element 117, etc to exist even for a fraction of a fraction of a second in cosmic events? Or are these elements only possible in a lab?

Thank you

Californium (98) in particular has an isotope (250) with a 13 year half-life. Typically the higher the number of protons above 91 the shorter the half-life, so 117 is probably under a second, but Californium is in that middle range where it can exist for long enough to be processed.

kzb
2015-Aug-18, 03:57 PM
I believe it is standard theory that transuranics are indeed produced in supernovae.

There is an idea that supernovae make some superheavy isotopes with longer half-lives than can be produced in the lab. This is because the same intensity of neutron irradiation can't be reproduced on Earth, so all our superheavy isotopes are neutron deficient. There are longer lived isotopes with more neutrons, but they have not been able to make them with current technology.

Hornblower
2015-Aug-19, 01:10 AM
If I am not mistaken, there are believed to be some sweet spots in the atomic number range upwards of 110 analogous to uranium and thorium. I don't remember any details.

swampyankee
2015-Aug-19, 02:41 AM
I believe* that plutonium has been observed in stellar spectra, and it would seem that some of the longer-lived transuranics could appear if the supernova is bright enough for their spectra to picked out of the background. Any chance of one nearby enough to get very detailed spectra over many wavelengths over the next couple of decades? It would also be beneficial if it's far enough away to avoid causing any problems.












* that means I read it long ago, but don't remember the reference.

StupendousMan
2015-Aug-23, 05:39 PM
Hello,

I have heard mixed reports of the element Californium (98) being observed in supernovae.

Independent of this claim, is it at all physically possible for transuranic elements like Californium, element 117, etc to exist even for a fraction of a fraction of a second in cosmic events? Or are these elements only possible in a lab?

Thank you

The idea goes back to an article by Baade, Burbidge, Hoyle, Burbidge, Christy, and Fowler:

http://articles.adsabs.harvard.edu/full/1956PASP...68..296B

who noticed a coincidence between the decay time of Californium and the light curve of Type I supernovae.
In recent years, that idea has been discarded: other nuclear processes are responsible for the
characteristic times in supernova light curves.

There is no evidence for observations of any transuranic element in a star, as far as I know. I did some
checks using ADS and couldn't find any reports of detections. The closest was a non-detection
in the enigmatic and very well-studied Przybylski's star:

http://arxiv.org/abs/astro-ph/0610611

Sure, transuranic elements are very likely produced in certain explosive events in supernovae,
and they will last just as long in space as they do in our labs (as far as we can tell).
They just aren't common enough, and long-lived enough, for us to detect at the moment.

kzb
2015-Aug-24, 12:04 PM
Back in the 1970's, it was reported that primordial plutonium-244 had been measured in rocks. This isotope is difficult to make on Earth by successive neutron capture, because its precursor Pu-243 has a very short half-life, ie it decays before it absorbs another neutron. So it was argued that the Pu-244 must've been of supernova origin.

I believe that later work has refuted this original detection. But the point is, no-one argued that Pu-244 wouldn't be made in a supernova.

The expectation is that it is made. It's highly likely that other transuranics are made too, because of the intense neutron flux.

ngc3314
2015-Aug-24, 12:57 PM
The idea goes back to an article by Baade, Burbidge, Hoyle, Burbidge, Christy, and Fowler:

http://articles.adsabs.harvard.edu/full/1956PASP...68..296B

who noticed a coincidence between the decay time of Californium and the light curve of Type I supernovae.
In recent years, that idea has been discarded: other nuclear processes are responsible for the
characteristic times in supernova light curves.


Hm - I thought for sure I remembered gamma-ray detections of Cf, but may have been thinking of the (well-established) Al-26 mapping of the Galaxy. Radioactive, yes, made in supernovae, sure, but not transuranic.