Wikipedia:Reference desk/Archives/Science/2021 February 7

= February 7 =

Do Earth observatories better than space telescopes?
Do Earth observatories better than space telescopes? Even first Black hole image was produced by using observatory. Rizosome (talk) 02:17, 7 February 2021 (UTC)
 * Define "better". ←Baseball Bugs What's up, Doc? carrots→ 02:19, 7 February 2021 (UTC)


 * Also, the image was produced by a global set of radio telescopes, as this NG article explains: ←Baseball Bugs What's up, Doc? carrots→ 02:58, 7 February 2021 (UTC)


 * This is largely explained at space telescope. You can often find the answers to your questions more quickly by doing even a tiny bit of searching. Matt Deres (talk) 03:09, 7 February 2021 (UTC)

I am comparing two things. Rizosome (talk) 06:22, 7 February 2021 (UTC)


 * If Earth observatories were indeed "better" than space telescopes, why do you think would anyone spend millions of dollars on developing them? Earth observatories and space telescopes are used for different purposes, so you do indeed need to specify what you mean by "better" if you want a meaningful answer, but it would be easier to actually study the articles, and then come back with a more specific question.--Shantavira|feed me 09:29, 7 February 2021 (UTC)

What is the diagonal line in this satellite image?
In this satellite image, there is a long straight diagonal line in the upper left corner cutting across a headland of the westernmost island and with a slight but abrupt and arbitrary change of shade all across it. What does it represent? Is it natural? StellarHalo (talk) 06:04, 7 February 2021 (UTC)
 * Even at high resolution, I can't see what you describe.--Shantavira|feed me 09:32, 7 February 2021 (UTC)
 * I can see a line heading away from the island on a bearing of about 7 or 8 degrees (i.e. slightly to the east of north), if that's the one? It's rather faint, so much so that I wonder why it is of concern? I suspect it's natural, but how to tell? PaleCloudedWhite (talk) 09:46, 7 February 2021 (UTC)
 * So that island is Ushant, yes? I can also see a lighter line, which crosses the island, at about 15 degrees from due North. I suspect it's an artefact of the image construction. Either that or maybe a secret underground tunnel between France and Plymouth. Martinevans123 (talk) 10:00, 7 February 2021 (UTC)
 * You're right about the heading - I misread my protractor. I suspect that the tunnel theory is going off at a bit of a tangent though (pun intended), even by my standards of protractor competence.... PaleCloudedWhite (talk) 10:13, 7 February 2021 (UTC)
 * You can thank my trusty perspex school protractor.... What, no tunnel?? I'll have you know I "put the ys in Wikypedya". Martinevans123 (talk) 10:32, 7 February 2021 (UTC)
 * The line is there, but I think it's an artefact. Sentinel-2 tells us the satellite is in a sun-synchronous orbit with a descending node at 10:30 local mean solar time. That means that the satellite made a pass to the SSW in the morning or to the NNW in the evening. Shadows clearly indicate this picture was taken during the morning pass (it would be after sunset in the evening). So the line appears to be parallel to the satellite's ground track. Maybe some effect in the detector? Or, Sentinel-2 scans a strip 290 km wide and the image, when measured perpendicular to the line, is about 180 km. Maybe the northwestern most part was filled in from a different observation? Sentinel-2 (consisting of 2 satellites) makes 1 or 2 scans of this area every 5 days. PiusImpavidus (talk) 10:37, 7 February 2021 (UTC)
 * I see a long line, going from the left to the top edge of the image and cutting through the eastern headland of Ushant at a bearing of 21°, and another one, much harder to detect, passing between the two ships close to the upper left corner at a bearing of 16.6° (assuming "up" is true North). Can these be an artifact of image stitching? I cannot think of a plausible natural origin. --Lambiam 10:42, 7 February 2021 (UTC)
 * Oh dear, my trusty school protractor has just delaminated. Martinevans123 (talk) 10:53, 7 February 2021 (UTC)
 * I see several, parallel, at regular intervals across the watery parts of the whole image: along the north coast, from Ushant, Neïz Vran, Brignogan-Plages, Trégondern, Ploumanac'h; and the south coast from Brignéoc'h, Guilvinec, Merrien. I agree with : most likely they are image construction artefacts. Bazza (talk) 11:39, 7 February 2021 (UTC)
 * My guess is that we would be talking about an underwater pipeline. Passing watercraft seem oblivious of it. Then again, they might be aircraft. They have beautiful "plumages" stretching to the right. Each craft seems to give off its own color. Bus stop (talk) 01:55, 8 February 2021 (UTC)
 * One of the diagonal lines slices through the contrail of one of the aircraft, so that the "blue" and "green" copies of the contrail don't match up on the left and right sides of the diagonal line. The blue and green contrails have also changed their order (green on top to the left of the line; blue on top to the right of the line). This suggests that from one side of the line to the other, we have changed direction -- either the direction of scanning or of the satellite's motion during different passes. --Amble (talk) 22:54, 8 February 2021 (UTC)
 * Here's a web page explaining the arrangement of detectors on the Sentinel-2 MSI focal planes: . They are in a staggered pattern where each covers only part of the field of view.  The order of the bands reverses from one to the next.  There's a small overlap region in the middle.  This appears consistent with the stitching you're seeing. --Amble (talk) 23:02, 8 February 2021 (UTC)
 * Yes, I concur with your observations. There is a possibility that it is an illusion, but just as you say, the "blue" and "green" copies of the contrail don't match up on the left and right sides of the diagonal line. The blue and green contrails have also changed their order (green on top to the left of the line; blue on top to the right of the line). Not having any expertise in this I am reluctant to state with any degree of assuredness what is going on, but it appears as an error in "stitching" together sections. Bus stop (talk) 06:00, 9 February 2021 (UTC)
 * There are three images of the aircraft: in red, green and blue, in order of decreasing wavelength. The multiple imaging may be caused by the focuses being optimized for coincidence at sea level, so that objects at different altitudes have non-coinciding foci for the three wavelengths and have accordingly displaced images. Reversing the order of the bands may also cause the reversal of the order of these displacements. --Lambiam 13:06, 10 February 2021 (UTC)

Americium in smoke detectors
How much Americium is in a smoke detector? Is it all Americium? UB Blacephalon (talk) 22:41, 7 February 2021 (UTC)
 * The general subject is discussed in Americium. — Preceding unsigned comment added by Baseball Bugs (talk • contribs) 23:18, 7 February 2021 (UTC)
 * So is it all americium? I've heard people say that not all of the button is americium. Is this true? UB Blacephalon (talk) 23:29, 7 February 2021 (UTC)


 * The article says a typical smoke detector uses 0.3 micrograms of Americium.  That means that if you somehow extracted the pure Americium from 10,000 smoke detectors, your pile of Americium would weigh about the same as an ant. ApLundell (talk) 23:54, 7 February 2021 (UTC)
 * How dangerous would it be? Is pure americium? UB Blacephalon (talk) 01:33, 8 February 2021 (UTC)
 * Read the article, for a sense of the danger level. ←Baseball Bugs What's up, Doc? carrots→ 04:09, 8 February 2021 (UTC)
 * It doesn't say anything about purity. Is it pure? UB Blacephalon (talk) 04:32, 8 February 2021 (UTC)
 * This is explained in the article.
 * "The process for making the americium used in the buttons on ionization-type smoke detectors begins with americium dioxide. The AmO2 is thoroughly mixed with gold"
 * ApLundell (talk) 05:17, 8 February 2021 (UTC)
 * So its not 100% Americium but AuAmO2? Damn.... 00:43, 9 February 2021 (UTC)
 * No, mixing it with gold does not make it a compound with gold. Nor does it necessarily impact the danger. Unless it is being surrounded by something that absorbs ionizing radiation (which wouldn't make much sense, since its purpose is to use said ionizing radiation), then it doesn't matter what it is mixed with or surrounded by. What matters is how many moles of the element are their, what isotope of the element it is, and its distance from the living organism that would be impacted by it. The amount of it in a smoke detector is not dangerous. --OuroborosCobra (talk) 18:06, 9 February 2021 (UTC)
 * Oh so is the majority americium? Is there a way to purify it? UB Blacephalon (talk) 01:30, 10 February 2021 (UTC)
 * Again, it's purity is entirely irrelevant. Radioactive decay is not governed by sample purity. The decay rate is a first-order process, a half-life. If you have 0.3 micrograms of Americium-241 in your smoke detector today, then in 432 years, you will have 0.15 micrograms of Americium-241 in your smoke detector. Whether it is surrounded by gold or plastic or glass, whether it is incredibly low in purity within whatever matrix contains it, all is entirely irrelevant. All that matters is how much Americium-241 is in the smoke detector. --OuroborosCobra (talk) 01:59, 10 February 2021 (UTC)
 * Well, hmm, I don't think that's exactly true. Americium-241 is an alpha emitter, and alphas have very poor penetrating power.  If your americium were dispersed through a thick matrix, most of it would be wasted, because the alphas would be absorbed before they ever got to the detection chamber.  It doesn't matter how "pure" it is per se, but it does matter how much stuff is between it and where the alphas need to go.  I would speculate that it's deposited thinly on a foil surface or something. --Trovatore (talk) 06:32, 10 February 2021 (UTC)
 * |I addressed that in an earlier comment I made in this discussion, but Blacephalon doesn't seem to be as interested in the ability of a smoke detector to function at all as much as he is "will it kill me" and "how pure is it," as well as a question that I really don't know how to answer of "is all the americium made of americium." I mean, all of the oxygen atoms in water molecules are, in fact, oxygen atoms, just as all of the americium in a smoke detector is, in fact, americium. That's true regardless of the purity of the radio source material. All of the americium in it is americium, whether is constitutes 100% or 1% of the matrix. The surrounding matrix certainly might impact how well the smoke detector works, but not whether the americium atoms are americium atoms, and not their decay rate. --OuroborosCobra (talk) 21:22, 10 February 2021 (UTC)
 * So its just americium, that's the point? Huh, oh well a bit of Americium is enough I suppose. The most I can do is just keep collecting samples. Its not like its THAT dangerous, right? UB Blacephalon (talk) 06:12, 10 February 2021 (UTC)
 * I do not know what you mean when you say "it's just americium." Americium atoms are americium atoms, yes, no matter what you surround them with, no matter if they are in a compound or not. The oxygen atoms in water are all oxygen atoms, that isn't impacted by the presence of hydrogen. The chairs in my office are all chairs, even if there are also some couches and computers in the same room. The purity of the ionization radiation source in the smoke detector has no impact on whether the americium atoms are americium atoms. If the atoms have 95 protons, 95 electrons, and and 146 neutrons, then they are americium-241, and if the number of neutrons is different, they are still americium atoms in general (though different isotopes of that element). That said, I would advise against trying to collect all of the americium you can from lots of samples of smoke detectors. First off, why would you even want to do such a thing? What purpose do you have for collecting that much americium? Second off, the more you have altogether that you are exposing yourself to at once, the more radiation you will be receiving. I don't feel like sitting down and doing the math on how much americium-241 you would need to have to be dangerous or how many smoke detectors that would be. Alpha-radiation has a very low ability to penetrate materials, and even your skin can block most of it, but if, while working with it, you accidentally ingested or inhaled any americium, you would then have an alpha-emitter inside your body, which could be dangerous. If you do not know proper procedures for handling radioactive materials, and given your line of questioning I highly doubt you have formal training in radiation safety, do not do whatever project this is. --OuroborosCobra (talk) 21:22, 10 February 2021 (UTC)
 * What I'm talking about is the fact that, as an example, silver might not be not totally pure. It can be 99.999% pure, it can be mixed in with other metals. The purity of silver can be questioned. Same with Americium. How pure is it when its first made? I get that it turns into other metals over time but at this point, I doubt much of it has happened. And I know that it can be harmful but I do know enough to be safe. I've been learning on my own time the different levels of radiation and what's powerful enough to stop it. Besides,I have a 10 mL plastic vial. Its gonna take a while to get enough smoke detectors for Americium to be dangerous. The reason I'm doing this is because I'm an element collector. Not a professional one but still, I want to get every element I can and as pure as I can get it. UB Blacephalon (talk) 03:29, 11 February 2021 (UTC)


 * It sounds like the question is "what fraction of the emitter (Am plus gold plus whatever-else) is actually americium"? As a start, a 1981 ORNL report notes "The sources of ionizing  radiation  used in ICSOs consist of...of a 0.002-mm-thick mixture of gold and 24lAm that is hot-forged onto a 0.2-mm-thick silver backing and covered by a 0.001- to 0.002-mm-thick gold foil." So the Am/Ag is about 0.5% by volume if you can get just the emitter out of the surrounding metal structure (see photo to right).
 * Taken another way, the ORNL report says the source is 3–5 mm wide, so let's back-of-envelope/ballpark from there. By eye the the object in the picture looks about 20 mm diameter and 5 mm thick. That gives a volume of 1.5 cm3, for approximate mass of approximately 4 g (based on it mostly being solid aluminium, as the image-description page notes). The description says it contains 141 ng 241AmO2, which is about 125 ng Am. So the object is 31x10–7% by mass 241Am. DMacks (talk) 04:16, 11 February 2021 (UTC)
 * Taken another way, the ORNL report says the source is 3–5 mm wide, so let's back-of-envelope/ballpark from there. By eye the the object in the picture looks about 20 mm diameter and 5 mm thick. That gives a volume of 1.5 cm3, for approximate mass of approximately 4 g (based on it mostly being solid aluminium, as the image-description page notes). The description says it contains 141 ng 241AmO2, which is about 125 ng Am. So the object is 31x10–7% by mass 241Am. DMacks (talk) 04:16, 11 February 2021 (UTC)


 * David Hahn sourced material for his experiment from smoke detectors, etc --TrogWoolley (talk) 15:20, 11 February 2021 (UTC)
 * Ahh ok I have already gotten the americium out of the button so is it AuAmO2? Is there any way to purify it? UB Blacephalon (talk) 19:19, 11 February 2021 (UTC)
 * You need to stop doing this. You are not trained in safe handling of radioactive materials. You could seriously harm yourself. --OuroborosCobra (talk) 20:47, 11 February 2021 (UTC)
 * Ya but I am interested in it. Next up, Californium! UB Blacephalon (talk) 21:46, 11 February 2021 (UTC)
 * And after that, the cancer ward.
 * Methinks this discussion should be shut down. ←Baseball Bugs What's up, Doc? carrots→ 22:22, 11 February 2021 (UTC)
 * Why? I only wanted to know how much of the button is americium. I still never got the answer...UB Blacephalon (talk) 03:59, 12 February 2021 (UTC)
 * I explicitly told you yesterday: "141 ng 241AmO2, which is about 125 ng Am" for one model, and ApLundell told you "0.3 micrograms of Americium" for a modern-design ballpark barely an hour into this discussion. Asked and and answered repeatedly, so shall we close this thread now? DMacks (talk) 14:28, 12 February 2021 (UTC)
 * Oh ok so it is pretty pure. Sure why not. UB Blacephalon (talk) 20:04, 12 February 2021 (UTC)