‘It seems very frightening. Do the stars really die like human? What happened after its death?’

‘Yes, stars will die after the exhaustion of nuclear fuel, and as mentioned previously, a lot of heavy stars of the first generation has already died; but the heavy elements generated by these massive stars are recycled by supernovea and form the terrestrial planet and human. These heavy elements are also essential for the formation of light, stable and long lived stars in the later generations of stars in form of dust grains.’

FATE OF THE UNIVERSE>THE DEATH OF STARS>SUPERNOVAE AND THE SOLAR SYSTEM

It is possible that the collapse of interstellar clouds is triggered by the shock wave from adjacent supernova explosions. A fascinating clue points to the interaction of a supernova with the interstellar cloud from which our solar system formed. Studies of samples of few large meteorites, which have yielded enough material for a rough chemical analysis, have revealed the presence of anomalies in the abundances of certain isotopic species. The anomalies are found in small embedded regions, or inclusions, where the composition differs significantly from the surrounding meteoritic material. The ratios of certain isotopes in the inclusions differ markedly from terrestrial ratios. One of the key results has been the discovery of trace amounts of a rare isotope of magnesium (Mg²⁶) in aluminum-rich meteoritic inclusions. The magnesium isotope does not occur naturally on the earth, but in the inclusions, the greater the degree of aluminum enrichment, the more Mg²⁶ is found. Radioactive decay converts an unstable isotope of aluminum (Al²⁶) into Mg²⁶; the conclusion seems inescapable that the Mg²⁶ has been produced in this manner. What is intriguing is that the decay time (or half-life) of Al²⁶ is only 1 million years. The unstable radioactive aluminum isotope has no long-lived progenitor; it is indisputably the parent species of the observed rare magnesium isotope.

The aluminum must have been produced in a supernova explosion, according to our present understanding of the origin of the elements. Radioactive aluminum-rich debris evidently was produced in the supernova explosion and solidified within less than 1 million years after the supernova event, before any appreciable dilution of the aluminum-rich material with interstellar matter could occur. The supernova would have immediately preceded the formation of the meteorite and thus also the formation of the solar system. One million years is a brief instant of time by cosmic standards. In fact, it is more or less equal to the time it would take a dense cloud, once its collapse was triggered, to fragment into stars.

Thus, we may reasonably conclude that some meteoritic debris found on earth has come undiluted from a nearby supernova explosion that immediately preceded the formation of the solar system. According to one hypothesis, the supernova debris condensed into tiny solid grains as it expanded and cooled. The grains acted rather like shrapnel, blasting their way into the collapsing interstellar cloud from which the solar system was destined to develop. The grains became incorporated into meteorites as the solar system formed.

The sun and the billions of other similar stars are the end products of this sequence of events. During the first 500 million years of the galaxy, massive stars evolved rapidly and created most of the heavy elements, which were distributed around the galaxy by supernova explosions. Billions of years later, the solar system formed from the ashes of the ancient stars that had been swept up into an interstellar cloud. About 5 billion years after the collapse of the interstellar cloud destined to form the solar system, one end product of this evolutionary scenario, the meteorite, fell upon another end product, the planet earth, and was examined by yet a third end product, intelligent life.