Here Be Dragons

HERE BE DRAGONS
Milky Way, our home galaxy. Its 300 billion stars merge into a broad
river of light. Just a minute fraction of them, that happen to be close to
us, form the myriad sparkling points that we call "the stars," yet even
these few seem numberless. It's hard to doubt that, on a planet orbiting
one of those stars, a living creature is gazing back at us.
To tell whether any of the stars really do have planets, and whether
any of these planets are inhabited, seemed for centuries an impossible
task. Even today, the world's greatest telescopes, such as the Hale telescope
at Palomar, the twin Keck telescopes on Hawaii, and the Hubble
Space Telescope, are incapable of spotting planets around other stars:
not because the planets are too faint, necessarily, but because they
cling too close to their bright parent stars. Yet a series of brilliant innovations
has allowed astronomers to detect a handful of such planets
indirectly and even to describe their basic properties, such as their size
and orbital characteristics, as we'll describe in the next chapter.
Even more exciting than the detection of extrasolar planets, though,
is our dawning understanding of the evolution of stars and their planetary
systems, an evolution that may carry the seeds of life from the
very beginning, even before a star and its planets are formed. Not
many years ago, it was possible to believe that our Sun, with its nine
planets—at least one of them inhabited—was a freak that might not
be repeated within our galaxy. Now, though many details remain unresolved,
we can speak of the birth of stars and their planets as one of
the fundamental processes of the cosmos, and we can tentatively explain
how the chemical building blocks of life take part in this process,
making an extraordinary journey from deep space to end up in living
creatures such as ourselves.
As we look up into the night sky, the winter constellation of Orion
dominates the scene. The mighty hunter, followed by his dogs (Canis
Major and Minor), chases Taurus the bull eternally westward. Orion
straddles the celestial equator—the circle, oblique to the ecliptic,
which lies directly over the equator of the Earth. Almost everyone recognizes
this dramatic constellation and its brilliant individual stars
with their exotic names: Betelgeuse, the variable red giant in Orion's
shoulder; Bellatrix, in Orion's other shoulder; and the blue-white giant
Rigel, the sixth brightest star in the sky, in Orion's foot. Most striking,
though, are the three close-set stars that form Orion's belt and the
fainter line of stars that dangle from it, forming his sword.
It wasn't till 1610, apparently, that anyone noticed something peculiar
about the middle star in Orion's sword. A French lawyer,
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