Andromedae

Searches for the element on earth have been fruitless, and it now appears that promethium is completely missing from the earth s crust. Promethium, however, has been identified in the spectrum of the star HR465 in Andromeda. This element is being formed recently near the star s surface, for no known isotope of promethium has a half-life longer than 17.7 years. Seventeen isotopes of promethium, with atomic masses from 134 to 155 are now known. Promethium-147, with a half-life of 2.6 years, is the most generally useful. Promethium-145 is the longest lived, and has a specific activity of 940 Ci/g. 

Figure 2.12 Andromeda Galaxy. (A colour reproduction of this figure can be seen in the colour section). (Reproduced from photos by courtesy of NASA)...

The three broad classifications (elliptical, spiral and irregular) of star clusters that also cluster together to form the Local Group that contains the Milky Way and the Andromeda Galaxy, along with the Small and Large Magellanic Clouds... 

Local group The collection of galaxies, including the Milky Way and Andromeda, that form part of the Virgo cluster as part of the local supercluster of galaxies. 

Figure 2.12 Andromeda Galaxy. (Reproduced from photos by courtesy of NASA)...

Progress in understanding stellar evolution and nucleosynthesis, and the discovery by Merrill (1952) of the unstable element technetium in the S star R Andromedae, demonstrating the occurrence of stellar nucleosynthesis within a few half-lives of Tc (i.e. < about 1 Myr see Fig. 1.8), has led to acceptance of the idea that abundance variations among stars are perfectly natural as a consequence of three main effects (see Fig. 3.37) ... 

Promethium is a silvery-white, radioactive metal that is recovered as a by-product of uranium fission. Promethium-147 is the only isotope generally available for smdy. The spectral lines of promethium can be observed in the light from a distant star in the constellation Andromeda. Even so, it is not found naturally on Earth, and scientists consider it to be an artificial element. Its melting point is 1,042°C, its boiling point is estimated at 3,000°C, and its density is 7.3 g/cm. ... 

I wanted to hurl him down the stairs rather than let her touch him. I wanted to scream at her to be careful, because she had been chained to the rock like Andromeda, fodder for the monster. 

Although new stars (novas and supernovas) had been observed for many centuries, as can be seen from Chinese, Japanese and Korean chronicles, the modern, scientific age of supernovas only began on 31 August 1885, when Hartwig discovered a new star near the centre of the Andromeda galaxy. Eighteen months later the new star had disappeared. 

In 1919 Landmark estimated the distance to the Andromeda galaxy at some 700000 light-years. (Current estimates put it at 2 million light-years.) It was clear that Hartwig s star was a thousand times brighter than any known nova. It was the same Landmark who suggested a connection between the supernova observed by Chinese astronomers in 1054 (the year of the religious schism) and the Crab nebula. 

An event similar to the Andromeda supernova was observed in 1895 in the galaxy NGC 5253. This time the new star grew brighter than its host galaxy. 

Edwin Hubble measured the distance of several Cepheids in the great Andromeda nebula and found that it was situated far beyond the globular clusters in the retinue of the Milky Way. It was then that the milky designation galaxy made its entry into astronomy. The age of extragalactic astronomy had... 

A light-year is the distance that light travels in one year at a velocity of 186,000 miles per second. How many miles is it to the galaxy in Andromeda, which is said to be 650,000 light-years away ... 

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