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Star Stuff

"We are such stuff as dreams are made on..." Well loath as I am to challenge the Bard on his home turf perhaps "We are such stuff as stars are made on..." is more literally true. I call upon Mighty Orion to attest to this truth. In the Hunter's constellation, we can see the entire cycle of stellar birth, death and rebirth. Orion holds a stellar nursery [Great Nebula], infant stars [Trapezium] and a star close to death [Betelgeuse].

Huge masses of hydrogen and helium gas with traces of other elements form the Great Nebula. Gravity causes this nebulosity to collapse in upon itself. Friction and compression elevate various regions to 15 million degrees Kelvin and a star is born. When the temperature rises this high, four hydrogen atoms at a time are able to fuse making a helium atom..

In this fusion process a tiny bit of mass is lost as each atom of helium is formed. Einstein's famous equation e=mc² tells us that energy from this tiny speck of mass is large because c² is such an enormous number. Electromagnetic radiation, mostly in the form of fierce gamma radiation, pours out. Above the central fusion core, masses of unfused gas soften the lethal energy until it shines forth at the surface as friendly starlight. Starlight excites the Great Nebula until it glows like a fluorescent lamp.

Within the Trapezium, we see stars that are mere infants. To ephemeral like us, they seem ancient but for stars with lifetimes in the billions of years, a million years is scarcely a week old. We see at least a half dozen stars in our telescope in a region less than a third of a light year across. Each of these stars is brighter than the Sun and some of them are multiple stars too close to separate optically. Our nearest neighboring star is more than 4 light years away. If we lived in the Trapezium, we'd see a dozen stars a hundred times brighter than any in our sky. Unseen masses radiate strongly in the infrared. Hot, but not yet hot enough to fuse hydrogen these masses await their turn to be born as stars. Soon (as stars count time) the Trapezium nursery will have additional infants.

One of our sky's half dozen brightest stars marks Orion's right shoulder, but bright as it is, Betelgeuse is no longer a healthy star. It is a red giant, swollen a hundred times its original diameter. If Betelgeuse replaced our Sun, it would engulf Mercury, Venus, Earth and the Moon. Mars would ride just above its ragged surface.

Stars have a life cycle as do all things in the universe. As stars exhaust their hydrogen fuel, their cores become primarily helium. The region of nuclear fusion begins to approach the surface of the star. Seeking equilibrium, these stars become red giants. Deep in the core temperatures soar to 100 million degrees. Helium and hydrogen now fuse in wild array. Red giants manufacture every natural element in their nuclear furnace cores.

Near the end, nuclear fusion ebbs as the fuel runs out. Gravity, long held at bay by nuclear energy, restarts the collapse of the star. Red giants live on borrowed time awaiting the catastrophe which will destroy them. Supernovae explode with a force beyond comprehension. In a brief moment, the star shatters utterly spreading its star stuff across time and space.

Is this the end of the story? Well, not quite. Long after the supernova recedes, another stellar system forms from dusty clouds laced with the star stuff forged in the old red giant's core. In one such system, in the oceans of the third planet around a new star, tides from a large moon stirred the star stuff. Somehow a living cell arises from the elements that had once been a star. More than four billion years later, this cell's most advanced descendants, in awe and wonder, dream about it all. We are, indeed, such stuff as stars and dreams are made on.

I hope you will join us at the Observatory on the next clear Friday night so that we can show you these wonders. A half century's observation is not enough for me to be jaded by their magnificence. Just for fun, we'll toss in Jupiter and Saturn, lots of their swarming moons, some globular clusters and a galaxy or two. Bundle up and we'll meet you there.

Leslie Coleman
Author:
Leslie Coleman
Entry Date:
Feb 1, 2000
Published Under:
Leslie Coleman's Columns
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