Benford, Gregory - Life at Galactic Center

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GREGORY BENFORD

LIFE AT GALACTIC CENTER

We're not in a lucky part of the galaxy, at least for views.

Our sun is tucked down in the disk's plane, though this took centuries to

realize. In retrospect, perhaps it is puzzling that astronomers did not guess

until the nineteenth century that the Milky Way is a disk, seen edge on.

Ancients used water analogies to describe it, images of rivers and streams. How

much easier matters might have been if we could have seen the truly gaudy

attraction in all the galaxy, the brilliant center.

Perhaps, thought, our ignorance is good luck. Dark dust clouds block our view in

the constellation Sagittarius, so we cannot see in the optical frequencies

beyond the edge of our local spiral arm. Beyond that are immense dark lanes,

blotting out the next arm and the hub beyond.

One way to see the center would be to live much nearer. But that could be fatal.

The galactic center is about 25,000 light years away. We orbit about two thirds

of the way out into the spiral disk, a benign, even boring neighborhood. The

nearest star, Alpha Centauri, is 4.2 light years away, an average stellar

separation for our region, where there is a star in roughly every fifty cubic

light years.

Were we to approach the galactic hub, well past the dust clouds, we would find a

halo of stars glowing brightly, growing ever denser. In 1932 Carl Jansky

discovered that, to his shock, the galactic center was the brightest radio

location in the sky, outshining even our sun. Something was going on.

In the core, within a few light years of the exact center, there are a million

stars within a single light year. On average, the nearer stars are only a

hundredth of a light year away. This is only ten thousand times the distance

from the Earth to the sun. Imagine having several stars so close they outshine

the moon.

As one might expect, this is bad news for solar systems around such stars. Close

collisions between all these stars occur in about a hundred thousand years,

scrambling up planetary orbits, raining down comets upon them as well.

The galactic center is the conspicuous Times Square of the galaxy -- and far

more deadly than the comfortable suburbs like ours. Joel Davis's Journey to the

Center of Our Galaxy details how horrific it is, points out that the survival

time for an unshielded human within even a hundred light years of the core is

probably hours.

I began studying the galactic center in the mid-1970s, out of curiosity. I did

not guess that this mysterious region would intertwine two of my passions,

physics and science fiction, though in part I was interested because I had begun

writing a series of novels which seemed pointed in that direction.

The first was In the Ocean of Night, exploring the discovery that computer-based

life seemed dominant throughout the galaxy. The action followed a British

astronaut, Nigel Walmsley, cranky and opinionated. It detailed a few incidents

in our solar system, in the late twentieth century and beyond, which uncovered

the implication that "evolved adding machines," as Walmsley put it, had

inherited the rains of earlier, naturally derived alien societies.

As I began work on the next volume, I realized that the galactic center was the

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Benford, Gregory - Life at Galactic Center

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