dipper@utastro.UUCP (Debbie Byrd) (10/27/86)
How the sun makes energy -- in a minute. October 27 The Amazing Sun The sun is a star because it shines, or produces its own energy. And the sun is able to shine because of thermonuclear fusion reactions taking place deep in its interior. Fission is where heavy atoms are split to make energy. Fusion is where light atoms fuse together under conditions of high temperature and pressure -- like those at the center of the sun. With fusion, four atoms of the lightest and simplest element, hydrogen, fuse to make a slightly different element, helium. But one helium atom is slightly less massive than the four hydrogen atoms which built the helium atom. This leftover mass is converted to energy which later floods out from the sun in the familiar form of light and heat. Energy flowing from the sun's core to its surface takes about 10 million years. If the sun's energy production suddenly ceased, we wouldn't know it until 10 million years from now. The sun has been churning out energy for some four and a half billion years. Again, it feeds on itself -- in a process where matter is converted into energy. One ton of matter -- completely transformed -- would supply the energy needs of the entire human race for about a year. But the sun makes much more energy than that -- it consumes and radiates away its mass at a rate of four million tons per second. The sun has so much mass it could continue to do this for 100 billion years -- but it won't. It'll only use the hydrogen located near its core -- and so will continue to shine as we know it for about another five billion years. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin
pmk@prometheus.UUCP (Paul M Koloc) (10/29/86)
In article <1363@utastro.UUCP> dipper@utastro.UUCP (Debbie Byrd) writes: >How the sun makes energy -- in a minute. >October 27 The Amazing Sun > >The sun is a star because it shines, or produces its own energy. And >the sun is able to shine because of thermonuclear fusion reactions >taking place deep in its interior. .... . Fusion is where light >atoms fuse together under conditions of high temperature and pressure >-- like those at the center of the sun. > >With fusion, four atoms of the lightest and simplest element, hydrogen, >fuse to make a slightly different element, helium. But one helium atom >is slightly less massive than the four hydrogen atoms which built the >helium atom. This leftover mass is converted to energy which later >floods out from the sun in the familiar form of light and heat. There are additional "particles" generated by the fusion reaction itself, called neutrinos, and these "slippery little buggers" flit through the sun's dense plasma almost as easily as if they were moving through a vacuum. Most other forms of ... . >Energy flowing from the sun's core to its surface takes about 10 >million years. If the sun's energy production suddenly ceased, we >wouldn't know it until 10 million years from now. Almost true!. We are keeping track of the the neutrinos, and it's a good thing too, apparently someone left the burner on simmer, 'cause we are only picking of half of what we should be finding. Of course, as Debbie points out, by the time the lights are dimmed at the surface of the sun, we should have talked DoE-DoE out of the money needed to development a fusion concept that will really work. That "half" came from a "long time ago", so correct me if I'm wrong! +---------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II, Ltd.; College Park, MD 20740-0222 | this | | {umcp-cs | seismo}!prometheus!pmk; pmk@prometheus.UUCP | decade | +---------------------------------------------------------+--------+
ethan@utastro.UUCP (Ethan Vishniac) (10/30/86)
In article <300@prometheus.UUCP>, pmk@prometheus.UUCP (Paul M Koloc) writes: > > Almost true!. We are keeping track of the the neutrinos, and > it's a good thing too, apparently someone left the burner on > simmer, 'cause we are only picking of half of what we should be > finding. Of course, as Debbie points out, by the time the lights > are dimmed at the surface of the sun, we should have talked DoE-DoE > out of the money needed to development a fusion concept that will > really work. > > That "half" came from a "long time ago", so correct me if I'm wrong! > Actually it's almost a factor of three. Moreover there is some (controversial) evidence that the remaining signal has some correlation with the solar cycle. The most likely interpretation of that would be that some neutrinos are generated through cosmic ray interactions with the upper atmosphere. This would be slightly modulated by changes in the size and strength of the magnetic field, which in turns depends on the interaction between our magnetic field and the solar wind. Nevertheless I would rate the possibility that the sun is turning off as fairly low. More likely we have some detail about the structure of the core wrong (since we are only sensitive to the high energy tail of the neutrino distribution) or some detail about neutrino physics wrong. There is a possibility that the electron neutrinos created in the sun could be converted, with near 100% efficiency into other kinds of neutrinos before leaving the sun. -- "More Astronomy Ethan Vishniac Less Sodomy" {charm,ut-sally,ut-ngp,noao}!utastro!ethan - from a poster seen ethan@astro.AS.UTEXAS.EDU at an airport Department of Astronomy University of Texas
jbuck@epimass.UUCP (Joe Buck) (11/01/86)
In article <300@prometheus.UUCP>, pmk@prometheus.UUCP (Paul M Koloc) writes: << Almost true!. We are keeping track of the the neutrinos, and << it's a good thing too, apparently someone left the burner on << simmer, 'cause we are only picking of half of what we should be << finding. In article <1369@utastro.UUCP> ethan@utastro.UUCP (Ethan Vishniac) writes: >Actually it's almost a factor of three... >Nevertheless I would rate the possibility that the sun is turning off >as fairly low. More likely we have some detail about the structure >of the core wrong (since we are only sensitive to the high energy >tail of the neutrino distribution) or some detail about neutrino >physics wrong. There is a possibility that the electron neutrinos >created in the sun could be converted, with near 100% efficiency >into other kinds of neutrinos before leaving the sun. Three types of neutrinos are known: the electron neutrino, the muon neutrino, and the tau neutrino. It is my (possibly confused) understanding that if the neutrino has a nonzero rest mass, there should be an "oscillation": the neutrino will interconvert among the three types. This makes the factor of three very interesting. There are some proposals to build muon neutrino detectors; this may shed some light on the issue. Disclaimer: I am not a physicist. However, I avidly read every particle physics or astrophysics article Scientific American, or other reasonably accessible sources, prints (too bad Science 86 is dead), and that's where this information comes from. -- - Joe Buck {hplabs,ihnp4}!oliveb!epimass!jbuck Entropic Processing, Inc., Cupertino, California
ethan@utastro.UUCP (Ethan Vishniac) (11/03/86)
In article <592@epimass.UUCP>, jbuck@epimass.UUCP (Joe Buck) writes: > >Me: > >Actually it's almost a factor of three... > >Nevertheless I would rate the possibility that the sun is turning off > >as fairly low. More likely we have some detail about the structure > >of the core wrong (since we are only sensitive to the high energy > >tail of the neutrino distribution) or some detail about neutrino > >physics wrong. There is a possibility that the electron neutrinos > >created in the sun could be converted, with near 100% efficiency > >into other kinds of neutrinos before leaving the sun. > > Three types of neutrinos are known: the electron neutrino, the muon > neutrino, and the tau neutrino. It is my (possibly confused) > understanding that if the neutrino has a nonzero rest mass, there > should be an "oscillation": the neutrino will interconvert among the > three types. This makes the factor of three very interesting. There > are some proposals to build muon neutrino detectors; this may shed > some light on the issue. > You get the full factor of three this way only through "maximal" mixing, i.e. if the mixing angles are all equal and large. This is possible, but (as I understand it) not particularly likely. A recent suggestion is that if neutrinos have small masses and mixing angles then the order of masses is affected by the presence of a sufficiently dense plasma. Normally we expect the electron neutrino to be the least massive. Interactions with the plasma could make it the most massive. If the plasma parameters change sufficiently slowly as the neutrino emerges from the sun then the wave function corresponding to the most massive neutrino in the core of the sun (electron neutrino) will correspond to the most massive neutrino in a vacuum (tau neutrino). It is possible to get conversion to muon neutrinos instead. In either case the detection of neutrinos in our experiments are unlikely to actually imply anything about neutrinos from the sun. It would be helpful to see muon neutrinos. It is somewhat easier (in fact it's being done now) to look for lower energy neutrinos. A change in the temperature profile of the sun's core wouldn't lower the flux of lower energy neutrinos. Screwy particle physics would. -- "More Astronomy Ethan Vishniac Less Sodomy" {charm,ut-sally,ut-ngp,noao}!utastro!ethan - from a poster seen ethan@astro.AS.UTEXAS.EDU at an airport Department of Astronomy University of Texas