Here Be Dragons

THE DEATH AND LIFE OF STARS
duced the warping, however, the hypothesized planet remains just
that—hypothetical. Direct detection of extrasolar planets, where life
might not only originate but evolve and thrive, requires more specialized
techniques, as we'll see in the next chapter.
The disk around Beta Pictoris is now usually described as a "debris
disk," implying that it consists, not of the original gas and dust that
collapsed to form the star, but of material thrown off during collisions
between asteroids, planetesimals, or other objects. While the predominant
infrared radiation comes from micron-sized particles, the disk
may well contain many larger rocky or icy objects. In fact, it may resemble
the Kuiper belt that encircles our own solar system.
So far, the observations on young stars support the notion that planets
form by gradual accumulation of smaller objects within a circumstellar
disk. The disk model also seems to help explain the particular
kinds of planets that we see in the solar system and their relative positions.
There is likely to be a gradient of temperature within a disk,
with the inner regions being hotter than the outer. Thus, within the
inner regions, only rock and metals can condense and form the objects
that later aggregated to form planets. This offers an explanation
of why Mercury, Venus, Earth, and Mars are all relatively small, rocky
planets. In the frigid outer regions, on the other hand, ices can also
condense, adding greatly to the mass of the planets forming there.
Those planets are also able to grow larger simply by virtue of their
longer orbits, which contain more material available to be swept up.
And once past a certain mass, the outer planets can attract and hold
onto a dense atmosphere of hydrogen and helium, derived from the
disk. This is why the outer planets—Jupiter and Saturn especially—
became the solar system's "gas giants."
Is this, then, the pattern we should expect to see repeated over and
over again across the galaxy Are myriad suns surrounded by clones of
our own solar system Gazing at the night sky from the dome of the
Hale telescope at Palomar, we can only ponder the question, as so
many have pondered before us. But technology is finally closing in on
the answer. Part of that technology lies housed below us in the darkness:
the Palomar Testbed Interferometer, the prototype for an astronomy
of the future, hugs the mountaintop like a colossal three-legged
spider. Within its hublike central building, technicians are putting
starlight through an optical maze, hoping to squeeze celestial secrets
out of it.
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