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The Sun: The Facts
• The Sun is a nuclear fusion reactor the size of a million Earths. The Sun's powerhouse is its core, an incredibly violent place where the temperature rises to 15 million degrees, and a one square metre cube of core material would weigh 150 tons. In this giant nuclear fusion reactor, atomic nuclei of hydrogen are smashed together and fused into helium. If only 1 kilogram of hydrogen were converted into helium in this way, enough energy would be released to satisfy the needs of 600 Americans for one year.

• The Sun burns 600 million tons of hydrogen every second. Put another way, 4 hundred million million million million million million hydrogen nuclei are converted into helium every second. In this process, over 4 million tonnes of the Sun's mass vanishes every second, converted into energy via Einstein's famous equation E=mc2. This is equivalent to exploding one hundred thousand million megatons of TNT per second. At this rate, it has enough fuel left for around 5 billion years, at which point it will die.

• The Sun today is made up of 74% hydrogen, 25% helium, and small quantities of other, heavier elements. These heavy elements seem negligible, but, in fact, the only place they can be made in the Universe is deep inside the hearts of stars. Just after the Big Bang, the only elements present in the Universe were hydrogen, helium and very small amounts of a handful of the lighter elements, but crucially no carbon, oxygen or iron. Everything in your body today, except the hydrogen, was cooked inside generations of ancient stars, and thrown back into the Universe when those stars ran out of hydrogen fuel and died a spectacular death known as a supernova explosion.

• The Sun is a third generation star, which formed around 4.5 billion years ago, a time when the Universe was already around 9 billion years old — enough time for two previous generations of stars to have lived and died. The Sun, planets and everything we see around us, including ourselves, formed from giant clouds of dust and gas thrown out into space during the deaths of these early stars.

• The Sun seems to be unique, and overwhelmingly important to us, but is, in fact, one of more than a hundred thousand million stars in our galaxy alone, and there are at least a hundred thousand million galaxies in the observable Universe. So the Sun isn't very special. In fact, as stars go, it's pretty small and unremarkable. A familiar star to anyone who looks up at the night sky is Betelgeuse in Orion (the bright red star, the ninth brightest in the sky). If our Sun were replaced with Betelgeuse, all the planets up to and including Jupiter would be inside the star! Its radius is 6,500 times that of our little Sun.

• In SUNSHINE, the Sun's inevitable demise happens not in 5 billion years, but during the 21st century. How could this be? While we have a reasonably sound and well-tested picture of the inner workings of stars, there are certainly things in the Universe we do not understand. Where I work at CERN in Geneva, a new 27km-long machine called the LHC (Large Hadron Collider) will be switched on this year. It will recreate the conditions that were present in the Universe less than a billionth of a second after the Big Bang. In these early times, a host of strange things could have been created, and these as yet undiscovered objects could still be flying through the Universe today. It is just possible that these objects could cause havoc if they drift into the heart of a Star.

• Many physicists believe that a new family of particles called Supersymmetric particles might be discovered at the LHC. They are a strong candidate for Dark Matter, the mysterious stuff discovered by Astronomers that makes up a much larger fraction of the mass in the Universe than the familiar families of particles that make up the Earth, the Sun and indeed eve


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