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Good answer. That thing is so distant that it seems to exist only in our fertile imagination

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>I think that freezing should allow one to achieve sterilization with a low emission source by basically tilting the replication rate to kill rate in a severe way.

>Low emission rate sources need more time to achieve sterilization.

>Still though, depleted uranium generally provides alpha and beta emissions with a bit of gamma. The alpha won't make it through the walls of the ampule. I think that much of the beta also won't make it through. You'll be dependent on the low gamma emissions to slowly achieve your sterilization.

The 15 microsieverts per hour measurement should already take that into account. The uranium sample itself is in glass so all of the alpha and most of the beta should be contained.

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It's important to remember that cells are only really vulnerable to radiation damage when they are actively dividing because it's only in this stage that the DNA fragments are exposed and aren't attached to the 'scaffolding' used to securely store DNA in the nucleus. And when the DNA is stored it is readily repaired by the cell's repair mechanisms. (The DNA can still be repaired during cell division but the repair process is much easier to disrupt.) So you would have to concentrate alot of radiation energy directly into the stored 'DNA bundle', to cause enough damage to the DNA and the structure used to support it in order to overwhelm a cell's repair mechanisms. The only way to do this at this dose rate is to have the stored DNA hit by an alpha particle but the range of alpha particles from radioactive decay is so low that none would make it to your sample bacteria.

So if the bacteria are unable to move due to a lack of nutrients, and so not actively dividing, but are still at a temperature typical of their environment they would be incredibly resilient to radiation damage and you are unlikely to sterilize the sample.

Now if they were frozen it would be possible for the bundled DNA to accumulate enough damage over time to kill the bacteria once they were thawed but again not in any reasonable time frame with this does rate.

Fun fact: people who are cryogenically frozen will accumulate enough DNA damage from high energy cosmic radiation that they will effectively receive a lethal dose of radiation before being thawed if they are frozen long enough. Probably not the best financial investment over the long haul. #justsayin

edit: removed 'any reasonable time frame' from the second paragraph. / added 'at this dose rate' in the first paragraph.

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First, Oort cloud is a bit hypothetical, those objects are far enough away that they are not catalogued. At those distances, Sun looks like just a bright star, how do you observe a object so dimly lit?

That said, assuming they are there, they wouldn't really have had time to form a accretion disk. The objects are too sparce to interact with each other much and the periods are too long. A object 2000au away(which is considered lower bound of Oort cloud) on circular orbit around Sun has a period of 90 000 years. Outer Oort cloud objects can have periods in millions of years

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I think it's indeed a bit higher than the background radiation in that altitude, but something like an electron beam irradiator can output as much as 11000 Gray per SECOND, the dose required for sterilization is pretty high. Also, in some places like Ramsar (Iran) and Guarapari (Brazil) the background radiation can be as high as 40uSv/h but that's pretty rare

In terms of magnitude, 5x is about the same given the range of emmisivity that is observed with radioactive sources.

When one considers sterilization, one is looking for magnitudes of "kill". For instance, cooking chicken to FDA mandated temps results in log -6 reduction. One in 1 million salmonella survive the cooking process. I think that dental steam sterilization practices are going for log -9 reduction.

A multiple of 5 is not a considerable effect in the consideration of sterilization.

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I think that freezing should allow one to achieve sterilization with a low emission source by basically tilting the replication rate to kill rate in a severe way.

Low emission rate sources need more time to achieve sterilization.

Still though, depleted uranium generally provides alpha and beta emissions with a bit of gamma. The alpha won't make it through the walls of the ampule. I think that much of the beta also won't make it through. You'll be dependent on the low gamma emissions to slowly achieve your sterilization.

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>This is roughly the dose rate of simply being on a plane at cruising altitude.

My initial research suggested this rate was 5 times that of cruising at altitude, but your point is taken. Thank you.

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