Is Plutonium Found in Space Naturally?

[Andy DS]

TL;DR Summary

Are there elements beyond uranium out in the Universe

It has been stated unequivocally that there are no naturally occurring elements beyond uranium anywhere else in the universe but on Earth then I read that plutonium has been discovered in space. Assuming it wasn't put there by humans who's right?

 

[Ibix]

then I read that plutonium has been discovered in space.

Where did you read this? It's important to provide references - if you read it in something some clown posted on vixra that's a very different proposition to something you've read in Nature.

Plutonium does occur naturally on Earth in small quantities as a result of neutron capture by Uranium 238, so its mere existence in space wouldn't be particularly surprising. If you can link us to what you were reading we may be able to comment further.

 

[Andy DS]

The statement made about there being no elements beyond uranium in space was made by Prof Brian Cox in one of his TV documentaries. To be precise he said words to the effect that we can be certain that everything out there in the Universe is made of only 92 elements. The statement about plutonium in space was in one of the articles on phys.org which I can't find right now.

 

[Drakkith]

I'm sure Prof. Cox means there isn't substantial amounts of plutonium in space. You won't find ores of it in asteroids, or clouds of it hanging around, or see it on any emission/absorption spectra. There would be so little of it that it isn't really worth talking about.

 

[Bandersnatch]

It's more nuanced than just not existing, but the statement as presented is broadly correct.
There do exist certain natural processes, like supernovae (or the aforementioned neutron capture), that produce plutonium, together with a whole lot of even heavier elements. But its half-life is so short that it quickly decays to negligible amounts.
All the lighter elements have isotopes that are either stable or have half-lives comparable with the age of the universe, allowing them to stick around long enough to coalesce into new stars, planets, and everything that sprouts on them. Plutonium is just too short-lived to survive in anything more than trace amounts.
So, in a way, if you know where or when to look, you might find some in space. But you won't find anything 'made' out of it.
The same goes for even heavier elements, but their existence is even more ephemeral.

 

[anorlunda]

See https://en.wikipedia.org/wiki/Nucleosynthesis

That article lists PU as being formed by merging neutron stars, but all elements heavier than PU, no source other than man-made.

 

[collinsmark]

Plutonium-238 is used to power (and warm) many satellites and space probes. So yes, there is known plutonium in space, of course those space probes in question are all man-made though.

https://rps.nasa.gov/about-rps/about-plutonium-238/

 

[snorkack]

I'm sure Prof. Cox means there isn't substantial amounts of plutonium in space. You won't find ores of it in asteroids, or clouds of it hanging around, or see it on any emission/absorption spectra. There would be so little of it that it isn't really worth talking about.

Why not?
And the nucleosyntesis graph is manifestly false. Technetium is conspicuously found in stars. Best evidence of nucleosynthesis.
There is a lot of Ti-44 in supernova nebulae... half-life just 60 years.
Well, Pu-244 has half-life 80 million years!
Tc-97 and Tc-98 both have 4 200 000 years
Np-237 has 2 100 000 years
Am-243 has 7400 years, and also is a daughter of Cm-247, 16 million years
Bk-247 has 1400 years
Cf-251 has 900 years
So, what are the rapid neutron capture yields of sundry actinides and how much of them are seen in kilonova nebula spectra?

 

[Drakkith]

So, what are the rapid neutron capture yields of sundry actinides and how much of them are seen in kilonova nebula spectra?

That's a good question. I'm having trouble finding any detailed information on the abundance of these superheavy elements in supernova.

 

[Andy DS]

Many thanks for all your answers on this question. The reason I asked it was that the statement the prof made seemed so emphatic that there couldn't be any naturally occurring heavier elements out there, I took it to mean there wasn't even a trace of it but it that may not be quite true.
I understand the thing about the half-life of these elements being miniscule in comparison of the age of the universe but it seems the process that creates heavier elements may still be happening in the present.

 

[Andy DS]

That's a good question. I'm having trouble finding any detailed information on the abundance of these superheavy elements in supernova.

Recent research puts the process that creates heavy elements down to neutron star collisions and not supernovas as the energies involved aren't quite enough.
Edit...
I just had another look at the periodic table above that anorlunda posted and it clearly shows which elements are produced by certain cosmic events.

 

[Drakkith]

Many thanks for all your answers on this question. The reason I asked it was that the statement the prof made seemed so emphatic that there couldn't be any naturally occurring heavier elements out there, I took it to mean there wasn't even a trace of it but it that may not be quite true.

Ah, the pitfalls and ambiguity of human language.

 

[snorkack]

You won't find ores of it in asteroids,

Why not?
Plutonium 244 decays through 3 alpha and 2 beta decays:
Pu-244=U-240+α (81 000 000 y)
U-240=Np-240+e_- (14 h)
Np-240=Pu-240+e_- (1 h)
Pu-240=U-236+α (6560 y)
U-236=Th-232+α (23 400 000 y)

Now Th has chemical properties different from Pu. Notably, Th occurs basically exclusively as Th⁴⁺. Whereas Pu mainly occurs as Pu³⁺: Pu⁴⁺ exists only in strongly oxidizing conditions, which are rare in asteroids. Therefore in an asteroid, Pu-244 could well go into ores different from Th-232.

If you examine an ore of Th whose chemical composition and structure is such that it could not incorporate Th, but Pu, which contains the He formed from Pu (3 He atoms for each Th), and radiation damage... but of course no Pu for some Gy, is it an ore of Th, or Pu?
And it is the asteroids in Solar System that are 4+ Gy old. Extrasolar bodies that do not have cometary activity bright enough to form a visible coma, such as Oumuamua, are also asteroids, and do not have such lower bound on age. Do they contain Pu ores with actual Pu in them?

 

[Drakkith]

Why not?

Because it will have decayed by now.

 

[mathman]

Among elements up to 92 my impression is that 43 and 61 have no stable isotopes and 85 aand 87 isotpes are too short lived to be found naturally.

 

[anorlunda]

Among elements up to 92 my impression is that 43 and 61 have no stable isotopes and 85 aand 87 isotpes are too short lived to be found naturally.

I don't get it. The universe is very big, perhaps infinite. If there is a mechanism for production of any element, it happens continuously. Why mention half life?

 

[snorkack]

Among elements up to 92 my impression is that 43 and 61 have no stable isotopes and 85 aand 87 isotpes are too short lived to be found naturally.

The problem with elements 87 and 85 is rather their small branching fractions.

 

[mathman]

I don't get it. The universe is very big, perhaps infinite. If there is a mechanism for production of any element, it happens continuously. Why mention half life?

I was talking about what is on earth.

 

[snorkack]

Half-life is not the issue. Element 86 has half-life under 4 days, yet it is abundantly found on Earth and in our lungs.

 

[Drakkith]

The shorter the half-life, the harder it is to find the element/isotope outside its production point. For superheavy elements above plutonium, the rate of production is low enough and the half life is short enough that you will essentially never find them in nature.

One could say that they don't exist in nature, but obviously this isn't always meant to be taken 100% literal.

 

[snorkack]

The shorter the half-life, the harder it is to find the element/isotope outside its production point. For superheavy elements above plutonium, the rate of production is low enough and the half life is short enough that you will essentially never find them in nature.

Element 96 has half-life 16 million years. How much of U-235 on Earth is primordial, how much is daughter of Cm-247?
The reason element 86 is easily found in our lungs and element 96 is not is not that element 96 is short lived, but that element 86 is produced on Earth, element 96 elsewhere.

 

[Drakkith]

The reason element 86 is easily found in our lungs and element 96 is not is not that element 96 is short lived, but that element 86 is produced on Earth, element 96 elsewhere.

Which matches what I said quite nicely. And let's not pretend half-life doesn't matter. It's one of the two major factors determining which elements and isotopes can be easily found in nature and which cant, the other factor being how much is produced in the universe.

 

[snorkack]

Radon has half-life under 4 days - protactinium over 30 000 years. Radon is easily found in our lungs precisely because of its short half-life.

 

[Drakkith]

Radon is easily found in our lungs precisely because of its short half-life.

I'm not following you.

 

[Vanadium 50]

Me neither.

 

[Vanadium 50]

Summary:: Are there elements beyond uranium out in the Universe

It has been stated unequivocally

he said words to the effect

(1) That doesn't sound unequivocal to me.
(2) Brian's documentaries are popularizations, not scientific journal articles.
(3) 2B years ago there was a natural nuclear reactor on earth, which certainly produced plutonium as well as short-lived fission fragments. There is no reason there shouldn't be many such objects in space.

 

[snorkack]

Compare radon with radium then.
Radium has half-life 1600 years. Radon 3,8 days, thus 1/95 years.
There are equal numbers of radon atoms and radium atoms formed on Earth, because one radon atom is formed from each radium atom formed. Since radon has 150 000 times shorter half-life, there must be at any time 150 000 times fewer radon atoms on Earth than there are radium atoms.
But just because there are 150 000 times fewer radon atoms does not mean they are any harder to find than the radium atoms! Precisely because they are so short lived, there are as many radon decay events as radium decay events - and radon decays have higher energy.
Furthermore, radium compounds are nonvolatile, just like the compounds of its mother uranium, so radium only causes radioactivity of rocks which are radioactive anyway. Whereas radon is volatile and separates from radium and uranium. Which is why radon is easier to find on Earth than radium, and is found in places where radium is rare, like lungs.

 

[stefan r]

Przybylski's Star has plutonium in the spectrum.

I could not read the full paper because of pay wall but abstract here clearly says "plutonium".

You never "hear" about this star because no one knows how to pronounce it. It is a "peculiar spectrum showing an almost complete absence of vowels".

 

[collinsmark]

From Article:

Traces of rare forms of iron and plutonium have been found at the bottom of the Pacific Ocean, after some kind of cataclysm in outer space created this radioactive stuff and sent it raining down on our planet.

The extraterrestrial debris arrived on Earth within the last 10 million years, according to a report in the journal Science. Once it hit the Pacific Ocean and settled to the bottom, nearly a mile down, the material got incorporated into layers of a rock that was later hauled up by a Japanese oil exploration company and donated to researchers.

[Edit: I see now that @Keith_McClary started a whole new thread about this here: https://www.physicsforums.com/threa...rom-outer-space-found-on-ocean-floor.1003143/]

 

[Astronuc]

The statement made about there being no elements beyond uranium in space was made by Prof Brian Cox in one of his TV documentaries. To be precise he said words to the effect that we can be certain that everything out there in the Universe is made of only 92 elements. The statement about plutonium in space was in one of the articles on phys.org which I can't find right now.

The statement from Brian reflects conventional wisdom on the part of many. As collinsmark indicated, there is now evidence that ²⁴⁴Pu (t_1/2 ~ 80 million years) can be produced and be transported to Earth from a long time ago, relatively speaking.

PF discussion here
https://www.physicsforums.com/threa...rom-outer-space-found-on-ocean-floor.1003143/

 

[sophiecentaur]

I'm not following you.

I think the argument goes like this: There's a lot of (solid) protactinium in some places, It produces radon at a more or less constant rate but radon doesn't last long. So people will be exposed to a constant., low level of radon. The level is an equilibrium condition of production and decay.
Perhaps @snorkack 's statement could be modified to include the words "only" and "locally" somewhere. That point is actually made higher up by someone.

Poor old Brian Cox does his best to present a suitable subset of the facts but people have to treat his sayings as oracular. Yer average viewer wouldn't be prepared to give what he says the PF treatment.

 

[Andy DS]

Wow, I really started something here. Many thanks for the insights from all contributors.

 

[sophiecentaur]

Wow, I really started something here. Many thanks for the insights from all contributors.

That's often the risk on PF. You can never say that PF is casual about its Physics.

 

[snorkack]

I think the argument goes like this: There's a lot of (solid) protactinium in some places, It produces radon at a more or less constant rate but radon doesn't last long. So people will be exposed to a constant., low level of radon. The level is an equilibrium condition of production and decay.
Perhaps @snorkack 's statement could be modified to include the words "only" and "locally" somewhere. That point is actually made higher up by someone.

No, my argument is different.
First, protactinium actually produces actinon, not radon.
But the thing is: we do not detect radon, or actinon, by observing the atoms during their existence (short or long). We detect them by observing their decays.
Therefore, since one radium atom decays into one radon atom but has 150 000 times the lifetime, there will be 150 000 radium atoms per each radon atom. But we don´t detect the radium atoms anyway. Thus we will see just 1 radium decay and 1 radon decay. Radon decay has higher energy and more importantly, while radium stays in the solid rock alongside its mothers, also radioactive, radon migrates before decaying and getting detected.
Protactinium is longer lived but harder to find because it stays in rock and its mother (U-235) is less common than U-238.

 

[gmax137]

But just because there are 150 000 times fewer radon atoms does not mean they are any harder to find than the radium atoms! Precisely because they are so short lived, there are as many radon decay events as radium decay events - and radon decays have higher energy.

I think some of the other posters here missed your intent because, generally, "harder to find" is mentally conflated with "fewer." Your point is, "easier to find" may equal "easier to detect."