I have been wondering for a while could a star carry out nuclear fission instead of fusion? if so what percentage of stars would? and how would a planet rotating if react to it? in my belief if the universe is infinate yes there there maybe a star out there that uses fission. and that about .5% per galaxy do. but im not sure about the planet thing.
What the hell are you talking about? Why would infinity have anything to do with fission in stars? And where did you get .5%?
read the whole message idiot if you had read it you would understand that i am stating my opinion on the matter. any who as for the .5% per galaxy i figured that it couldnt be more than 1% per galaxy because we would have noticed it by now...
Stars consist mainly of hydrogen. Hydrogen cannot undergo fission - it is already as small as it can get.
Hi atreides, How much fissionable material is required to make a star? How little fusionable material is needed so that fusion doesn't outweigh fission? If elements are distributed randomly, how many stars would you expect to have the right proportions, considering that the universe contains about a billion times more fusionable atoms than fissionable atoms? How long would such a star last?
What exactly will happen when the elements below iron become rare? That is about the time you would see fission stars if it's possible right?
Good point ok so what but im open to many possibilities what if there are stars out there made of something other than hydrogen. but im not really pondering the possiblities i pondering how it would effect other things like planets and how it might work. besides you cant expect me to have all the answers im only 14...
Ah, OK. Ill try not to sound patronising, i dont like being patronised myself. But the idea of fission stars, hhmm, maybe in a scifi story... Im also not an expert on this, but after a quick google, you too can sound like one: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961112a.html Now, a star to start fissioning, I would think you'd more get just a large bang if you ever managed to get enough fissionable material together in one place to start fissioning. You know about critical mass? Put enough together, with uranium 238 (i think) is maybe a good handful, and it'll start fissioning. So you'd have a job getting a starful together. Unless you manage to get a truly gigantic amss together that holds together under its own gravity which sounds silly to me. So, basically i dont see fission being a viable option to contribute any particular energy to a star. As for talking about any star in the galaxy using it, well, youd have to find a big source of neutrons and suchlike somewhere that maybe wasnt radiating hugely in most of the standard frequencies of radiation.
It does sound impossible, but it does make me curios how a giant (order of size/mass of a star) mass of U-238 out in the middle of space. Or here's an idea... some sort of dust cloud of U238 with as much mass as a star and at the center of this rotating cloud is a small nuke. The nuke is set to go out after sufficient pressure is applied. The cloud rotates and eventually condences til it becomes basically a giant ball of U238, with a nuke at the center. This becomes denser and denser (due to gravity) until the nuke goes off, starting the chain reaction with the U238. It can't explode as a normal nuke does because of the inward pressure of the graivty. I'm not saying its possible, just a curious idea, probably good for scifi use at least. -AntonK
Well the thing that keeps a fusion star from blowing up is that the pressure from gravity and explosions from fusion balance each other out right? The more the pressure builds up, the higher the temperature goes up, and more fusion occurs. I don't think a huge wad of fissioning uranium could stay together...
thanks all. but now i need to know how a planet might react and how other things would react to it. here's a list of stuff. predict how each one would react 1. a planet: 2. astroids/comets: 3. possibilities of ET: 4. the star's death: thanks guys
Hi atreides, The solar system surrounding a Uranium star would not behave any differently on the face of it. However: The lifetime of the star would be much shorter, making evolution of complex life unlikely The surrounding material originates from the same source as the star, so planets would presumably be very dense and fairly radioactive The star would be small, dense, and not particularly bright, meaning that habitable planets would have close orbits and short years The end life of the star would be interesting... I guess type of supernova might result as the star ran out of fuel and the core collapsed
We could create small star! think about it if we had enough uranium we could put it up in space create a fission star. if it were small enough it would rotate us instead of us rotating it...
The problem is that U238 doesn't fission, U235 does. In its natural state, Uranium is conists of 99.28 % U238 and .715 percent U235. Uranium must be artificially enriched to about 5% U235 to maintain a fission reaction( As in a nuclear power plant) and at least 20% for bomb grade. Uranium also naturally decays into lead over time. U238 decays to Pb206 in with a half life of about 4.5 billion years, and U235 decays to PB 207 with a half life of 700 million yrs. Also, Uranium, like all other heavy elements are only formed in Supernovae explosions. Which means that it is only made in the presence of, and mixed in with other elements. You will never find a "Uranium cloud", at most, Uranium will only form a fraction of any dust cloud you may find. And even if such a concentrated pocket did initially form, by the time it contracted into a body, the majority of the fissionable U235 would have decayed into lead, preventing any fissionable mass from forming. Secondly , Fission works best with slow neutrons, As a result, as the temp of the fissionable material goes up, the efficiency of the reaction goes down. This one reason that Nuclear plants can't blow up and only melt down. Once the fuel gets to melting temp the reaction becomes self moderating. So even if you were to get such an enriched uranium mass to form, it would most likely never get hot enough to produce visible light.
