But theories persisted that an element might exist which would be very stable, despite having a large nucleus. How? Inside the nucleus, the nucleons (the protons and neutrons) are arranged in "shells" of different energy levels. When a shell is full, a new one must be started, which means adding a more energy, making the nucleus more unstable.Rather like the electron shells that surround the nucleus, the lowest energy situation - and therefore the most stable - occurs when a shell is full. The magic numbers are simply the numbers of nucleons that complete a shell: two for the first, eight for the next, then 20, 28, 50, 82 and so on. Nuclei possessing a "magic number" of protons or neutrons are surprisingly long-lived for their size.

The "doubly magic" isotope lead-208, for example, with 82 protons and 126 neutrons, lasts forever.Most scientists agree with the Polish physicist Adam Sobiczewski, who predicted in the 1960s that the doubly magic nucleus would have 114 protons and 184 neutrons. The elements close to the magic would also be relatively stable, existing on a so-called "Island of Stability" amidst the sea of unstable isotopes.How could you "cross" that Sea of Instability to the magic element? Bigger nuclei are normally made by bombarding smaller nuclei with nucleons in the hope that they fuse. However, the products of virtually all these interactions are incredibly unstable. Fusion needs nuclei with exactly the right energies in a head-on collision.Early in 1999, a team of scientists from the Joint Institute for Nuclear Research in Dubna, Russia, and the Lawrence Livermore National Laboratory in California, announced they had reached the Island of Stability, after 40 days bombarding a lump of plutonium with high-energy beams of a rare isotope of calcium. And for a magical 30 seconds, element 114 - with 175 neutrons - lived and died.

Thirty seconds might not sound much, but at the rarefied level of such elements it is an age; element 104 has a half-life of 0.3 seconds.Six months later, a team at the Lawrence Berkeley National Laboratory, California, created element 118 - and then, when it decayed, element 116.According to the predictions, elements 118 and 116 shouldn't have been on the "island" at all. A life-time of one millisecond had exceeded expectations; even if it had been created, it should have been far too unstable to hold together.Recently, Professor Adam Sobiczewski, of the Soltan Institute for Nuclear Studies in Warsaw, Poland, has forecast some surprising characteristics for super-heavy nuclei. Some of them should be hollow, or bizarrely deformed, with the protons and neutrons squashed into ellipsoids, or bearing strange lumps and bumps. For some combinations of protons and neutrons, a sphere is no longer the lowest energy shape.This doesn't mean that the magic element is less magic, but the theories surrounding it are changed.

The hopes of finding one with a lifetime of a year have faded Some say it may only last a few hours.. As Christmas draws ever closer, it will become increasingly difficult to ignore the planet Venus in the evening sky. By the end of the year, it will look like a brilliant lantern hanging in the west, setting a full four hours after the Sun - a dead-ringer for the Star of Bethlehem.

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As Christmas draws ever closer, it will become increasingly difficult to ignore the planet Venus in the evening sky. By the end of the year, it will look like a brilliant lantern hanging in the west, setting a full four hours after the Sun - a dead-ringer for the Star of Bethlehem. Was Venus the Christmas Star in the east that was supposed to have triggered the journey of the Magi? Almost certainly not - Venus makes such regular appearances as the "Morning Star" and the "Evening Star" that people observing the heavens even then would have been familiar with it. The Christmas Star must have been a celestial event that was truly out of the ordinary, even for the astrologers and soothsayers who kept remarkably detailed records of heavenly events.To track down the real Star of Bethlehem, we need the date of Jesus's birth.

To confuse matters, Jesus was not born in the year 0 (which doesn't in any case exist), or even in the year one. Thanks to a miscalculation in the calendar by a 6th century monk delighting in the name of Dionysius Exiguus, Jesus was actually born "BC".We know also that Herod was alive at the time of the birth, and that he died soon after an eclipse of the Moon - almost certainly in 4BC. So what astronomical portents were hoving into view at around that time? One we can definitely rule out is Halley's Comet, which swings close by the Sun roughly every 76 years. An unforgettable view of the comet in 1301 so inspired the Italian Rennaissance painter, Giotto di Bondone, that he used it as the model for his "Star" in a famous nativity scene. But astronomical records show that Halley's Comet came by in 12BC - too early for the birth of Jesus.At first sight, 5BC looks a bit more promising.