Superheavy stable elements

[piff]

You probably saw the article by Keith Cooper in the current issue of "Astronomy Now" magazine headed "The Impossible Star" concerning the discovery of actinides in Przybyski's star and the theories that have attempted to explain what these normally short-lived elements are doing there, and how they are replenished. One possible explanation offered in this article has been puzzling me and I was wondering if anyone can help me resolve my difficulty with it.  It is referred to as the "island of stability" theory put forward originally by Glenn Seaborg, suggesting that these actinides in the star's atmosphere could be the products of radioactive decay of a theoretical set of as yet unknown "superheavy" but stable elements which we have yet to discover or detect. They would supposedly be able to exist due to higher than normal neutron-to-proton ratios, and would initially be formed by an influx of neutrons such as would not normally be found except in the exceptional conditions inside massive stars. All of which sounds quite fascinating. However my difficulty is this: I have admittedly only a rudimentary understanding of sub-atomic physics, but to my mind it seems that an element that is "stable" would by definition not be liable to radioactive decay - is that not a contradiction in terms? And if so then obviously such elements, if they exist, would not give rise to decay-products. Am I missing something here?

[Dave In Vermont]

Well, the 'Periodic Table' is only able to get up further at the cost of "stability" if by being 'stable,' you mean it won't reach it's half-life faster you can blink your eyes. Any elements with increasing atomic-weight will, for all intents & purposes, vanish before we'd have an impossible task in actually creating them via a cylotron, or such, and actually studying them.

Last Analysis:

They'd be the antithesis of 'stable' in most ways of thinking. If anyone out there could use a Periodic-Table, these might be useful:

https://en.freedownloadmanager.org/Windows-PC/Periodic-Table-of-the-Elements-C-NET-Edition-FREE.html

 

 

Finding remnants of such high atomic-weight elements should be rather expected as the intense heat and pressure and such from the heart of an exploding star (nova) is off-the-scale. But transient - as a nova is thought to be a short-lived phenomena. But research is now indicating that our previous theories about these events is inaccurate. We've just found one such event that looks to be capable of happening periodically - 50ish years apart - and another nova-type event lasting for 3 years! So finding actinides with half-lives measured in nano-seconds isn't off the charts in the range of possibilities.

Star Exploded, Survived, and Exploded Again More Than 50 Years Later.pdf

&

Bizarre 3-Year-Long Supernova Defies Our Understanding of How Stars Die.pdf

These are interesting times in the world regards new findings in stellar-chemistry, astrophysics, and plethora of other inter-related sciences!

Enjoy!

Dave

[The Admiral]

I read that article too. A very interesting star, without doubt.

My understanding is that they believe they have detected these transuranics, the actinides. They are radioactive and have relatively short half-lives, but even then we can be talking about tens of thousands of years. Still, this is miniscule compared with the life of the star, so there must be something continuously generating them. Now this can be done by building them up in a highly neutron rich environment, as we do on earth in nuclear reactors, or through the radioactive decay of even more massive nuclei. The problem is, as the more massive a nucleus becomes, so the shorter its half-life becomes. In other words, such more massive nuclei would disappear even faster than the transuranics. If you search for 'islands of stability', you'll find articles which discuss the prospect that some way beyond the nuclei we can currently create, there may exist even more massive nuclei which are much more stable, and whose half-lives become significantly longer. I don't think we are talking of totally stable nuclei here, but perhaps nuclei with, I don't know, half-lives of millions of years, or at least comparable with the age of the star.

From what we are told of this star, it seems that the star's magnetic field is separating these elements in the star's atmosphere. So I wonder, given that these transuranics, and indeed Uranium itself, can be fissile, that in some of these 'shells' of elements fission reactions may be taking place, and creating the actinides in the same way as we do on earth. In which case we'd have a star undergoing both nuclear fusion and fission! Not in the realms of fantasy I would have thought

Ian

[TheMightyKong]

Interesting.

I wonder where promethium and technetium are formed.

 

[The Admiral]

Googling Promethium, it seems that it and only one other element, Technetium, have isotopes which are all radioactive. In other words, they essentially are not found in nature; if they ever were created cosmically, they are long gone. They will require artificial production.

Ian

[Macavity]

I remember it was a bargain basement paperback on "The Elements" that
first motivated me to take an interest in Science!

I haven't read all the above (nor the latest references!). But the so-called
"Island of Stability" (and Super-heavy Elements) has always intrigued!
So, rather randomly:

One of the interesting aspects of Nuclear Theory is the *analogous* idea
(c.f. electron orbitals) of the nucleon (proton/neutron) "Shell Structures".  

The stability problem for increased Atomic number is mostly down to the
large Coulomb repulsion of the protons. This is part "moderated" by the
neutrons and also favoured by *complete* shell occupancy -- So-called
"magic numbers" for spin-half Fermions in a general way: 2, 8, 18 etc.  

Fusion of lighter Elements cannot produce Neutron proportions needed
by the most stable isotopes of Super-Heavies. But it had previously been
speculated that "Neutron Rich Environments" around neutron stars may
be one possibility for production / existance such things...

"Stability" is relative! Half lives would still be measured in seconds? I sense
BULK production of such elements will never be possible anywhere? But the
idea is attractive... E.g. "Element 118" might be a "Noble Gas... Liquid"!

</wibble> 

[Dave In Vermont]

<Oy Vey!>

THUD!

As if Astatine wasn't enough to make me lose my Bismuth & neutron source...

I had a job-offer from a nuclear-physicist at Harvard who wanted me to act as his janitor and take all of his isotopes off to the incinerator. Not realizing I had an extensive background  in nuclear-science, he told be that once his collection of 'hot' materials had reached half-life, they were no longer radiation-emitters. And I should toss em' into the incinerator and burn them up - sending a plume out over the city of Cambridge, Massachusetts.

"Well Golly!! Jeeze, Gomer - I think I'll just be calling the Cambridge City Council's office and see what THEY think!"

I never heard from that <unprintable> again.

Dave

[Mr Spock]

4 hours ago, Dave In Vermont said:

the city of Cambridge, Massachusetts

Are you sure it's not Springfield... 

[Dave In Vermont]

Sure it was where they keep Harvard. But that menace may have been Homer.

Dave

[Stub Mandrel]

On 18/11/2017 at 19:59, Mr Spock said:

Are you sure it's not Springfield... 

That was my thought!

[Macavity]

If anyone fancies a "historic" purchase, just found my "The Chemical Elements" Book.
Author was Helen Miles Davis, with revisions by Glenn T. Seaborg (Pub. 1952, 59 & 61). 

http://www.ebay.co.uk/itm/The-Chemical-Elements-by-Helen-Miles-Davis-1961-Paperback-The-Rare-Earths-Good/162521093735?hash=item25d7031667:m:mypGDVm1DNAeSSwiTDCzvJA

I think it's a "Cool" book 'cos it contains transcripts of the original discovery papers...

Quote

"The triumphant chariot of Antimony, being a conscientious discovery of the many real transcendent Excelencies included in that mineral. Written by Basileus, a Bendictine Monke, faithfully Englished and published for the common good. By I.H. Oxon. London: Printed for W.S. and are to be sold by Samuel Thompson at the Bishop's Head in Pauls Church Yard. 1661". 

And so on...