2.3 Sticky Particles
15
mill star like our Sun is a long run indeed, lasting billions of years. If the mass of
the compressing cloud is too small, it may age into a brown dwarf in its cradle, or
remain a cold failed star.
Contrary to those beliefs placing paradise in Heaven, outer space is where the
most scorching hell is found. While the spiral branches of galaxies are relatively
peaceful (occasional explosions excepted), denser star populations in their inner
regions collapse into monstrous black holes, up to billions of times the solar mass.
The sight of a black hole is anything but black; their environments are the brightest
objects in the Universe, illuminated by streams of accreting matter that convert into
radiation a far larger fraction of its mass than even stellar nuclear fusion can achieve.
2.3 Sticky Particles
Back on our main track, we turn to the forms created by aggregation. Scaling down
from galaxies, we stop on the way to have a look at entities still exceeding our
measure – planetary systems. Cold debris, the leftovers of star formation, remained
orbiting the central body as it was warming up, collecting in a thin disk (Fig. 2.3,
left). The formation of planets from nebular gaseous clouds, not unlike galactic
material on a far larger scale, was proposed as early as in the 18th century, first by the
Swedish mystic Emanuel Swedenborg, then expanded by the young Immanuel Kant
(1755), before he delved into the philosophy of ethics and metaphysics, and in a
more detailed form by the great physicist and mathematician Pierre-Simon Laplace
(1796), who famously retorted to Napoleon that he had no need to invoke a God
hypothesis in his Syst` eme du Monde.
Universal theories, extending over widely separated scales, from the Solar System, still unexplored, to galaxies, still totally unknown, are characteristic of the 18th
century but not the 21st, which takes a more focused look and finds the detailed
Fig. 2.3 Left: Image of a protoplanetary disk around a very young star (a youthful hundred thousand years of age). Right: Artist’s image of a distant hypothetical solar system, similar in age to
our own
15
mill star like our Sun is a long run indeed, lasting billions of years. If the mass of
the compressing cloud is too small, it may age into a brown dwarf in its cradle, or
remain a cold failed star.
Contrary to those beliefs placing paradise in Heaven, outer space is where the
most scorching hell is found. While the spiral branches of galaxies are relatively
peaceful (occasional explosions excepted), denser star populations in their inner
regions collapse into monstrous black holes, up to billions of times the solar mass.
The sight of a black hole is anything but black; their environments are the brightest
objects in the Universe, illuminated by streams of accreting matter that convert into
radiation a far larger fraction of its mass than even stellar nuclear fusion can achieve.
2.3 Sticky Particles
Back on our main track, we turn to the forms created by aggregation. Scaling down
from galaxies, we stop on the way to have a look at entities still exceeding our
measure – planetary systems. Cold debris, the leftovers of star formation, remained
orbiting the central body as it was warming up, collecting in a thin disk (Fig. 2.3,
left). The formation of planets from nebular gaseous clouds, not unlike galactic
material on a far larger scale, was proposed as early as in the 18th century, first by the
Swedish mystic Emanuel Swedenborg, then expanded by the young Immanuel Kant
(1755), before he delved into the philosophy of ethics and metaphysics, and in a
more detailed form by the great physicist and mathematician Pierre-Simon Laplace
(1796), who famously retorted to Napoleon that he had no need to invoke a God
hypothesis in his Syst` eme du Monde.
Universal theories, extending over widely separated scales, from the Solar System, still unexplored, to galaxies, still totally unknown, are characteristic of the 18th
century but not the 21st, which takes a more focused look and finds the detailed
Fig. 2.3 Left: Image of a protoplanetary disk around a very young star (a youthful hundred thousand years of age). Right: Artist’s image of a distant hypothetical solar system, similar in age to
our own