Strange beasts in the stellar zoo.

• Author: Braffman-Miller, Judith
• Position: Science & Technology

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WE ARE SUCH stuff as stars are made of. In fact, we owe our lives to those glittering flecks of lovely light that party around our night sky like twinkling sprinkles of confetti. The universe was born in the Big Bang about 14,000,000,000 years ago with only hydrogen, helium, and trace amounts of lithium. Everything else was formed in the heats of stars working their nuclear-fusing magic as they transformed these primordial light elements into heavier ones. The oxygen we breath, water we drink, and iron in our blood all were created from elements formed inside our universe's billions and billions of stars as they spun their supply of hydrogen fuel into heavier items. There perhaps are as many as 400,000,-000,000 stars in our Milky Way alone. When a star reaches the end of its hydrogen-fusing (main-sequence) life, it blasts these heavier elements into space, where they then can fly off to become part of newborn baby stars and their resulting retinues of planets, moons, and living creatures. A starless universe would have been a lifeless one.

Our sun, at present, is a very ordinary main-sequence small star colored a lovely luminous golden yellow that dwells in the far suburbs of a typical, though majestic, barred spiral galaxy. There are planets and an assortment of other objects circling it. The sun, like all stars, will die eventually. Today, the sun is a middle-aged star. It has lived out approximately half of its life and, in another 5,000,000,000 years or so, will perish.

When the sun and other sunlike stars finally have used up most of their hydrogen fuel--and become elderly--their looks begin to change. In the heart of an elderly sunlike star resides a core of helium, encircled by a shell in which hydrogen still is being fused into helium. The shell starts to expand outward, and the core grows bigger as the star ages. The helium core itself starts to shrivel under its own weight, and it heats up until, at last, it becomes hot enough at the center for a new stage of nuclear burning to commence.

Now, it is the helium that is being fused to form the heavier element, carbon. Five billion years hence, the sun will have a small, intensely hot core that will be spewing out more energy than our still-vibrant sun is at the moment. The outer layers will have swollen up to monstrous proportions, and it no longer will be a small, yellow, ordinary star. It will have undergone a sea-change, becoming what is termed a red giant. The seating-hot, fiery-red, swollen elderly sun will swallow Mercury, then Venus, before it cannibalizes the Earth.

The core of our dying star will continue to shrivel and, because it no longer is able to chum out radiation via the process of nuclear fusion, all further evolution will be determined by gravitation alone. The sun ultimately will blow off its outer layers. The core, however, will remain intact, and all of the sun's mailer finally will collapse into this small relic body that...