back to article Physicists wrap neutrino detector in cosy blanket to shed light on the Sun's secondary fusion cycle

As we near the northern winter solstice, the Sun continues to produce a steady power output of 384.6 yottawatts resulting from the fusion of hydrogen into helium in two distinct nuclear reactions. Direct observation of the secondary cycle was published in the journal Nature for the first time yesterday. A team of physicists …

  1. John Smith 19 Gold badge

    "Then solar neutrinos scatter off electrons in a large vat of liquid scintillator "

    Is liquid. Can scintilate under the right circumstances.

    1. Neil Barnes Silver badge

      Re: "Then solar neutrinos scatter off electrons in a large vat of liquid scintillator "

      But it's better to scintillate than never...

      The one with the big book of bad puns in the pocket, thanks -->

    2. Francis Boyle

      And with all those

      carbon and oxygen atoms it's mostly metal. Enjoy your glass of liquid metal.

      1. Flocke Kroes Silver badge

        Astrophysicists love approximations

        Astrophysicists' periodic table: Hydrogen, Helium, Metals...

        (No joke icon. No sarcasm tag. This really is a popular approximation in astrophysics.)

        1. Brewster's Angle Grinder Silver badge

          Re: Astrophysicists love approximations

          And there's a question mark over helium - it's a bit suspiciously non-hydrogeny to not be a metal.

          1. Julz

            Re: Astrophysicists love approximations

            Ye but, there's quiet a lot of it about, as for the rest of these so called stable atomic configurations, there's hardly any of them so lump them all together I say.

          2. Blackjack Silver badge

            Re: Astrophysicists love approximations

            You could call it a funny gas?

        2. Anonymous Coward

          Re: Astrophysicists love approximations

          It's a good approximation though. Big bang nucleosynthesis is expected to have made, by mass, about 75% hydrogen, 25% helium-4, 0.01% deuterium and helium-3, some trace amount of lithium and essentially nothing else.

          So if you're interested in stars it makes complete sense to look at what they're made of in terms of 'stuff made in the big bang' (which to a really good approximation is hydrogen and helium) and 'stuff made later', where they call the stuff made later 'metal'. Knowing how metallic a star is tells you a lot of interesting things about it.

          1. bombastic bob Silver badge

            Re: Astrophysicists love approximations

            apparently unstable big bang proto-stars made the heavier stuff earliy on, within the first few million years or something like that. I remember seeing a discussion about that a few months ago, on the El Reg comment board

          2. Brewster's Angle Grinder Silver badge

            It helps to remember astrononmy is an old science.

            I think the usage was coined long before we knew about the big bang, that space was expanding or even that there were galaxies, and before we knew atoms had nuclei (remember the plum pudding model?) let alone that nuclei could fuse.

            It's probably because of where absorption lines are in the spectrum. So we looked at the sun and saw lines for hydrogen, helium and other "chemical metals". (In fact the helium line was initially though to be a line for sodium - a metal.) It was only later we discovered non-chemical metals were much more abundant.

            And it remains the case that most stars are hydrogen, helium and rounding errors. (Yes, that's because of the big bang, but you're looking at it backwards - if the big bang had produced a different pattern of elements it wouldn't matter provided stars had ended up as we see them today.) And when you look outside stars, helium becomes irrelevant; you find ionised hydrogen (HII), atomic hydrogen (HI), molecular hydrogen (H2), free electrons, magnetic fields and pretty-coloured soot.

            1. Anonymous Coward
              Anonymous Coward

              Re: It helps to remember astrononmy is an old science.

              Oh that's interesting. Do you have a reference for the history (this isn't doubting you – I'm willing to bet you know more than me about it! – I'd just find it interesting to read!)

        3. bob, mon!

          Re: Astrophysicists love approximations

          Way back when I was in college, I was told that an engineering equation was "good enough" if it was accurate to 3 decimal places; a physics equation was good enough if it was within an order of magnitude; and an astrophysics equation was good enough if the units came out correctly.

          That was in the days when slide rules ruled....

        4. Tom 7

          Re: Astrophysicists love approximations

          I wonder if, under 400000 miles of Sun the Hydrogen might not be metallic too.

          1. Claptrap314 Silver badge

            Re: Astrophysicists love approximations

            Gee..isn't it hot in here?

        5. DJO Silver badge

          Re: Astrophysicists love approximations

          As the universe is 92.7% Hydrogen, 7.16% Helium the other 0.14% hardly matters.

          (That's by number of atoms, by mass it's: 75% Hydrogen, 23% Helium, 1% Oxygen, 0.5% Carbon and 0.5% everything else)

        6. Anonymous Coward
          Anonymous Coward

          Re: Astrophysicists love approximations

  2. Chris G

    A large vat of liquid scintillator

    I am sure I drank one of those at a Christmas party a couple of years back, everything was bright and shiny........ until it wasn't.

  3. Anonymous Coward

    "The Borexino Collaboration"

    Forgive me for saying that this sounds like a coalition of consumer products companies that are managing some resource used in the production of household cleansers. :)

  4. bombastic bob Silver badge

    neutrinos are emitted when neutrons decay

    Just to keep everyone up to speed ln this, in the presence of a large gravity, a neutron can decay into a proton, an electron, and 2 anti-neutrinos. The reason for the particle count is conservation of spin; hence 1 neutron decays into two particles and two anti-particles. Mass+energy are also conserved, as well as momentum. So the decay product particle velocities will reflect any mass defect from the reaction as kinetic energy, and their resulting directions of motion will conserve momentum.

    This is why scientists believed the anti-neutrinos actually existed, because they apparently observed a difference between the mass+energy of the neutron vs its decay products, and possibly a difference in total momentum as well [implying the existence of unknown/undetected particles].

  5. Richard 12 Silver badge

    I for one welcome our scintillating liquid overloads

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