Sue Hartigan <[EMAIL PROTECTED]> writes:
Evidence of New Planets Is Cited
> WASHINGTON (AP) -- The clearest evidence yet of new
> worlds forming beyond the sun has been found by
> astronomers using sensitive new heat-seeking
> instruments focused on a star some 220 light-years from
> Earth.
>
> Astronomers announced Tuesday that they had found a
> doughnut-shaped disk of dust rotating around the star
> and that the hole in the doughnut probably contains
> newly formed planets.
>
> The finding, along with similar results published in
> the journal Nature by other astronomers, suggests that
> planets may be more common than once believed and this,
> in turn, makes extraterrestrial life more likely.
>
> ``Perhaps there are lots of places for life to exist,''
> said David Koerner of the University of Pennsylvania, a
> member of an astronomy team that co-discovered the
> doughnut-shaped dust disk.
>
> ``A solar system like our own is being constructed in
> the middle of this disk,'' he said.
>
> Another astronomy team, using the Cerro Tololo
> Observatory in Chile, made a confirming observation.
>
> Both teams focused on a star call HR 4796 that earlier
> studies had suggested could be at the center of what is
> called a protoplanetary disk.
>
> ``These disks are thought to be the birthing rooms of
> planets,'' said NASA astronomer Edward Weiler, head of
> a space agency program that is searching for evidence
> of extrasolar planets and life.
>
> ``We haven't actually detected any planets,'' said Lee
> Hartmann of the Harvard-Smithsonian Center for
> Astrophysics and a member of the Cerro Tololo team. But
> he said the most likely explanation for the absence of
> dust in the hole of the disk is that planets have
> formed.
>
> He said new and highly sensitive instruments are
> allowing astronomers to move ``from just speculating
> about planets forming to actually seeing it.'' Hartmann
> predicted many new planetary families will be
> discovered outside the solar system over the next few
> years.
>
> A new type of infrared detector attached to the Keck
> and the Cerro Tololo telescopes determined that the
> dust about HR 4796 existed mostly in a thin outer ring
> and that between this ring and the star there was an
> empty cavity. It's believed that this cavity was carved
> out by plants that swept up the dust in their birth
> process.
>
> A team of American and British astronomers tells this
> week in the journal Nature of finding the telltale
> doughnut holes in dust disks about three other stars:
> Vega, Fomalhaut and Beta Pictoris. These stars are
> older than HR 4796 and it is believed that planetary
> formation there is further along.
>
> As planets form, said the astronomers, they would tend
> to act like gravitation vacuum cleaners, sucking up the
> dust and gas from areas near their orbits. After all
> the planets are formed, only a faint outer ring of dust
> and gravel is left. Such a ring, called the Kuiper
> Belt, exists now around the sun, orbiting beyond Pluto
> and Neptune, the outermost planets of the solar system.
>
> ``This may be what our solar system looked like at the
> end of its main planetary formation phase,'' said
> Michael Werner of the Jet Propulsion Laboratory, who
> worked with Koerner and two other astronomers.
>
> He said comets may be forming now in the outer dust
> ring about HR 4796, just as comets are thought to have
> formed in the Kuiper Belt.
>
> The planetary disk orbiting HR 4796 is 18 billion miles
> across, while the cleared area, or doughnut hole, is
> about 9 billion miles across, slightly larger than the
> diameter of the solar system, the astronomers said.
>
> Stars are thought to form from the concentration of a
> gas and dust in the center of a cloud. The process
> causes stars to spin and the dust left over from
> stellar construction flattens into a disk.
>
> Some particles in the disk join, forming a
> gravitational base that attracts other particles,
> which, in turn, increases the gravitational attraction
> and draws in still more dust particles. This growth, or
> accretion, continues until planets are formed and most
> of the orbiting dust is swept up.
>
> The whole planetary process may take a few hundred
> million years of a star's 10-billion-year lifetime. As
> a result, said Hartmann, there is only a small window
> of time, relatively speaking, during which the
> construction of planets about a specific star can be
> observed.
>
> Weiler said astronomy is on the brink of having the
> instruments needed to actually see the ``pale blue
> dots'' of Earth-like planets orbiting distant stars.
> Early in the next century, he said, there will be new
> telescope systems in orbit that will actually
> photograph planets and take measurements of their
> oxygen and carbon dioxide, gases that are hallmarks of
> life.
>
> The National Aeronautics and Space Administration
> scientist said the new findings suggest planetary
> formation is not rare and may be, in fact, a common
> thing. This, he said, ``has a lot of implications for
> extraterrestrial intelligence.''
--
Two rules in life:
1. Don't tell people everything you know.
2.
Subscribe/Unsubscribe, email: [EMAIL PROTECTED]
In the body of the message enter: subscribe/unsubscribe law-issues
