Earth and solar system were born 4.5 billion years ago. Clues
to our genesis are fragmentary, so astronomers must look at
the birth of stars in neighboring stellar "maternity wards"
to see a replay of the events that created our Sun and planets.
studying debris disks, composed of dust and gas, whirling
around developing stars, the NASA Hubble Space Telescope's
high resolution has opened up a new level of detail that reinforces
earlier theories and offers some new surprises about planet
birth. The ultimate goal, which only may be realized by a
next-generation space telescope, will be to inventory planets
and solar systems around other stars and ultimately identify
1994 Hubble discovered dozens of dust disks around young stars
in the great Orion Nebula. Dubbed "proplyds" these disks are
widely considered to be precursors to full-fledged planetary
systems. Such disks were proposed in the eighteenth century
by Immanuel Kant to explain the simple fact that all the planets
of the solar system lie in nearly the same plane, and so were
born from a primordial disk that provided the raw material
for planet growth.
Hubble images may long be remembered as the first tantalizing
visual evidence that planets might be ubiquitous in the galaxy.
Dozens of stars in the Orion region which itself is
just one of thousands of star birth regions in the Milky Way
Galaxy have these disks. Though it is not clear if
they will go on to condense into planetary systems, their
abundance alone is firm visual evidence that the first baby
steps toward planet formation are very common.
Hubble telescope has also spied these disks around isolated
young stars ranging in age from 1 million to 10 million years.
Astronomers have used the Hubble's arsenal of cameras to capture
these disks in ultraviolet to near-infrared light. By chronicling
these disks at different stages of a star's early life, astronomers
are adding information to the planet-making recipe.
telescope's sharp vision analyzed disks around eight young
stars in the nearby constellation Taurus. Images taken in
near-infrared and visible light show that material falling
onto the disks are driving outflowing jets of gas from the
developing stars. Many of these disks are 8 to 16 times the
diameter of Neptune's orbit.
Wide Field and Planetary Camera 2 spotted the first example
of an edge-on disk in a young double-star system. These images
offer further evidence that planet formation should be possible
in binary star systems. Theory holds that gravitational forces
between the two stars tend to tear apart fragile planet-forming
disks. Astronomers also found evidence of dust in the disks
clumping together and beginning to make larger bodies.
at a disk around a slightly older star, astronomers using
Hubble's Space Telescope Imaging Spectrograph found evidence
of more clumping of material. The 2- to 4-million-year-old
star, called AB Aurigae, is in constellation Auriga. These
clumps are much farther away from the star than Pluto, our
outermost solar system planet, is from our Sun.
its gaze to a fully developed star about 10 million years
old, Hubble's Near Infrared Camera and Multi-Object Spectrometer
captured images of a 6.5-billion-mile-wide dust ring. This
ring around the star, called HR4796A, resembles Saturn's rings,
but on a larger scale. The gaps between the rings could be
the result of unseen bodies sweeping out lanes. The star is
220 light-years from in the constellation Centaurus.
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