By Tom Burns - Stargazing



People often identify me as an astronomer, but that couldn’t be further from the truth.

I am a stargazer. I know enough of the science to get by, but my concern is mostly with the beauty of the Cosmos and our place in it. Stargazers stand and look, with or without telescopes. They take with them not only everything they know about astronomy and its history, but also the lore and legend that every culture around the world uses to imbue the sky with meaning.

Every star has its own cultural and scientific story, and the experience of the heavens is vastly improved if you know a few of them, and perhaps, as I am doing now, pass them on to others.

The Crab Nebula in the constellation Taurus, the Bull, is a case in point. In my youth, I tried to see it in binoculars. But the light-polluted sky around Youngstown, Ohio, and my youthful inexperience doomed my efforts.

Finally, I was in graduate school and had a little money of my own. I cobbled together a telescope out of purchased optics, scrap plywood, and some house paint left over from the previous tenants.

There wasn’t much to be seen from inside Columbus, so my wife and I drove up to Mohican State Park.

What should I observe first? Remembering my youthful failure, I trained the telescope with some difficulty at an oval patch of light just above the bottom horn of the constellation Taurus, the Bull. And there it was, a dim thumbprint of light, the expanding remnant of a star that exploded almost a millennium ago.

My wife was deeply unimpressed by a fuzzy thumbprint. But to me, here was the dim echo of one of the most spectacular astronomical events ever recorded by humans.

In 1050, Chinese astronomers in the court of the Emperor saw a star where none had been seen before. They had no idea what stars really were, so the new star was little more than a fearsome curiosity. But they made careful observations anyway, perhaps in the hope that their notations would some day mean something.

The “guest star” blazed so brightly that it was visible during the day for three weeks. They watched it slowly fade to black over the following three months.

Seven centuries later in 1731, John Bevis discovered another curiosity, a misty patch of light, called a “nebula,” in the same location as the Chinese had observed the star.

These matters languished for two centuries. As telescopes finally got larger, astronomers began to discern details in the fuzz ball. The 19th century astronomer Lord Rosse described it as having “resolvable filaments” with a gap at its south end, which led to its nickname, the “Crab.”

In the first decades of the 20th century, astronomers began to make some sense of the Crab. By comparing photographs taken several years apart, they discovered that the nebula was rapidly expanding.

By studying its outward motion, they concluded that the expansion must have begun about 900 years earlier, and the connection with the Chinese guest star was finally established. It had all the earmarks of a stellar explosion of intense magnitude. The Crab had the distinction of being the first “supernova remnant” ever discovered.

Improved photographs of the object showed that it was blue at its center with filaments of red gas at its edges. Why was the gas producing different colors?

The answer came in the 1950s from Soviet experiments with a particle accelerator called a synchrotron. The Soviets discovered that electrons rotating in a powerful magnetic field produced a bluish glow of exactly the same kind as seen inside the Crab.

What then was causing the spinning magnetic field that in turn caused the electrons to whirl around? As astronomers pondered that question, they also began to use new technology telescopes to study stars in parts of the energy spectrum that visual telescopes cannot see. The Crab was emitting X-ray and radio energy, as they had come to expect from supernova remnants.

However, unlike most supernova clouds, the Crab was rich in those energy bands deep inside the heart of the Crab.

In the end, astronomers discovered a tiny and extremely dense star rotating at the center of the Crab. By studying its radio waves, they determined that it was like a celestial lighthouse beacon rotating at an unbelievable 30 times every second.

Other older supernova stars rotated much more slowly. This, then, was what happened when stars explode. Some of their material is ejected explosively into space. The rest collapses into a rapidly spinning ball. As the energy of its spin is converted over time into a massive magnetic field with spinning electrons, its rotation slows down.

The great Chinese mystery was at last solved, and it only took 900 years — a long, long time in human history but the smallest trifle in the life and death of a star.

I have observed much more spectacular objects in my time as a stargazer, and I have built and used much larger telescopes. However, nothing then or since quite matches that hazy view, that celestial thumbprint, that had generated such human scientific effort over almost 1,000 years. In my own insignificant way, I had joined the great chain of people who had felt the sense of mystery and accomplishment.

To truly appreciate the sky, you have to know that history. It also helps to know the myths and legends of cultures around the world. Only then can you appreciate the intensity of heart and head with which we as humans have venerated the sky.

A sense of familiarity also helps. The stars have been, nearly as much as family and friends, my dearest and most constant companions through life. I carry with me to every stargazing session a lifetime of memories.

If you are young, I envy you because there is still time to make them.

If you are old, there is time enough to make them for others. Take a child or two out to where the sky is clear and dark and learn together the beauty and the majesty of the universe one star at a time. When you are gone, your love of the Cosmos and all its parts will live on in them.

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By Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.