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Press Coverage E. This leaves only two possible isotopes for astronomical measurements, thorium Th or Thorium, with a half-life of Several age determinations have been made by means of the Thorium isotope. Its strongest spectral line is measurable with current telescopes in a handful of comparatively bright stars, including the Sun. However, the decay is really too slow to provide sufficiently accurate time measurements. This slow-moving clock runs forever, but is hard to read accurately!
The faster decay of Uranium would make it a much more precise cosmic clock. However, because uranium is the rarest of all normal elements, its spectral lines in stars are always very weak; if visible at all, they normally drown entirely in a vast ocean of stronger spectral lines from more abundant elements.
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Nevertheless, this is exactly where the low abundance of heavier elements in very old stars comes to the rescue. In the stars that were studied by the present team at the VLT, with typically times less of the common elements than in the Sun, the predominance of the maze of atomic and molecular lines in the spectrum is greatly reduced. The lines of rare elements like uranium therefore stand a real chance of being measurable. This is particularly so, if for some reason uranium atoms were preferentially retained in the debris of those early supernova explosions that also created the iron-group elements we see in the stars today.
The Half Life of Stars by Louise Wener
The excitement of the astronomers was great when they inspected the first spectrum of the 12th-magnitude programme star CS ! It showed what is probably the richest spectrum of rare, heavy elements ever seen. While only one or at most two thorium lines have ever been measured in any other stars, no less than 14 thorium lines are seen in the spectrum of CS Indeed, there is such a wealth of lines of other rare and precious metals that this spectrum is a real astronomers' treasure box. And best of all, the long sought-after line of singly ionized uranium is clearly detected at its rest wavelength of Not surprisingly, the uranium line is still quite weak.
After all, uranium is the rarest of elements to begin with and it has further decayed by a factor of eight since this star was born. Moreover, even in this low metal-abundance star, the near-UV spectrum remains rather rich in other lines.
The accurate measurement of this faint spectral line therefore places extreme demands on the acuity resolving power and efficiency of the spectrograph and the light-gathering power of the telescope. The VLT and UVES have been built as the world-leading combination of these observational assets, and the spectra obtained of this comparatively faint star magnitude 12, i.
Despite its faintness, the uranium line can therefore be measured with very good accuracy. Since these two elements were formed by the same atomic processes as their stable neighbours in the periodic table, this means that radioactive decay has progressed further in CS than in the Sun. Different models of the element production in supernova explosions predict somewhat different production ratios between the stable and radioactive isotopes, leading to age estimates for this star in the range billion years. The most likely age of CS is However, for the immediate future, the accuracy of this age determination does not really depend on the VLT spectrum.
For the time being, the real problems are the present uncertainties in the available laboratory data for uranium by means of which the measured line strengths are converted into element abundances.
The Half Life Of Stars A Novel 2006
In addition, the nuclear-physics calculations of the initial isotope production ratios introduce errors that are larger than those of the spectral observation. Thus, improved measurements of those physical data are necessary in order to read more accurately the cosmic clock in CS from the existing observational data.
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First, a quick Half-Life recap.
Perhaps Cave's agent said, 'My client has sheep-like fans who'll buy anything with his name on it'. It is bad compared to the worst piece of fiction this reviewer has ever encountered. He is an artist who has crafted witty but crucial insights for black America. Er, what can we say? It's no surprise that Gerard Way's graphic novel is being turned into a film.
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