"Benford-LifeAtGalactic" - читать интересную книгу автора (Benford Gregory)

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.