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Millions of new Comets Coming - Part 1 of 2

Astronews, Close Encounters - Millions of new Comets Coming (ASTRONOMY,
Aug 1999, p. 24):

Comet lovers may be heartened, while others will be frightened by recent
findings indicating that millions of new comets are destined to head our
way from the outer solar system. About 2.4 million comets will be
scattered toward Earth and a few could collide with us. However, there
is no need to panic: The comets won't arrive for a few million years.
A team of astronomers mapping out the traffic pattern of stars in our
solar system's neighborhood discovered the stars' destabilizing effects
on the Oort Cloud. Most long-period comets come from the Oort Cloud, a
vast, spherical reservoir of comets far beyond the planets.
Astronomers estimate that several trillion comets reside in the zone
that stretches 1 to 2 light-years from the sun - halfway to the nearest
stars. When a star passes near the cloud, the resulting gravitational
nudge can launch lots of comets toward the sun.
A team led by Joan Garcia-Sánchez of the Jet Propulsion Laboratory in
Pasadena, California, combined observations made by the European
Hipparcos satellite with those from the ground. The team's goal is to
determine which stars move closest to the sun during the past and future
10 million years.
In a paper published in the February issue of The Astronomical Journal,
the team wrote that Sirius, currently the brightest star in the sky,
will come within 7.5 light-years of Earth in 66,000 years. Barnard's
Star will come within 3.7 light-years of Earth in just 10,000 years. And
Proxima
Centauri, our solar system's nearest star, will brush within 3.2
light-years in 27,000 years. While all three come close, none is
expected to disturb the Oort Cloud.
However, the effect of GL 710, a currently obscure star, is more
worrisome. In just 1.4 million years - brief in astronomical terms - GL
710 will actually dip into the middle of the Oort Cloud as it passes
within 1.1 light-years of the sun.
To estimate the effect of the close encounter with GL 710, which is half
the sun's mass, the team ran a computer simulation. The conclusion: The
star would launch roughly 2.4 million comets on paths that will
eventually cross Earth's orbit. The storm will be spread out over about
2 million years, so only about one new long-period comet a year will
appear in Earth's traffic pattern. Still, when compared with the current
rate of about two comets per year, GL 710 will trigger a 50 percent
increase in local cometary traffic. (Richard Talcott)


Best regards,

Bernd

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