- WASHINGTON, D.C.
--- While most scientists want to know how our solar system began, Fred
Adams is more interested in how it will end. His prognosis is grim. In
the short term, we either freeze or fry. In the long term, we decay.
-
- Adams presented his vision of the solar system's fate
in a presentation at the annual meeting of the American Association for
the Advancement of Science held here Feb. 17-22.
-
- During the next 7 billion years, our aging sun will gradually
exhaust its fuel supply and collapse into a white dwarf, says Adams, an
associate professor of physics at the University of Michigan. The sun
will mushroom in size before it collapses and shine so brightly that it
will incinerate the Earth and the inner planets in the solar system. But
as soon as 3.5 billion years from now---long before the planets go up in
smoke---all life in the Earth's fragile biosphere already will have perished
from the heat.
-
- There is one escape clause in this fiery scenario, according
to Adams. We may be rescued by a close encounter between our solar system
and a passing star. Adams and Gregory Laughlin, a scientist at NASA's
Ames Research Laboratory, used a computer and statistical processing calculations
to model possible interactions between nearby binary stars and the orbits
of the Earth, sun and outer planets, especially Jupiter.
-
- "Jupiter is vulnerable to gravitational interactions
with a passing star," Adams explains. "Because of its large
mass, even a modest disruption of Jupiter's orbit could have a catastrophic
effect on Earth. The chances of such an encounter either hurling the Earth
out into space or plunging it into the sun during the next 3.5 billion
years are about one in 100,000."
-
- Should the Earth be thrown out of the solar system into
deep space, its oceans would not freeze solid for about 1 million years,
according to Adams. "Life could continue to thrive near hydrothermal
vents on the ocean floor, which are warmed by radioactive heat from deep
within the Earth," he says. In fact, Adams maintains that the most
likely place to find extra-terrestrial life may be in liquid oceans beneath
thick ice sheets on planets or moons of giant planets, such as Jupiter's
moon, Europa.
-
- In the far, far distant future---long after our solar
system has met its ultimate fate---the galaxy will move into what Adams
calls the Degenerate Era. "The only stellar objects remaining will
be white dwarfs, brown dwarfs, neutron stars and black holes," he
says. During this era, galaxies will begin to relax dynamically with some
remnants of stars moving out to the edge of the galaxy and others falling
to the center. Invisible dark matter gradually will be captured and converted
into energy to keep the few remaining white dwarf stars shining weakly
for a little while longer.
-
- "Eventually the supply of dark matter particles
will be exhausted," Adams says. "Then the mass of white dwarfs
and neutron stars will begin to dissipate through a process called proton
decay. A white dwarf fueled by proton decay would generate approximately
400 watts or enough to run a few light bulbs."
-
- Even black holes won't last forever. Fed by material
falling to the galaxy's center, black holes will grow larger for a long
time. But even their enormous mass must eventually dissipate into thermal
radiation, photons and other decay products.
-
- Once the black holes have radiated away, Adams says all
that remains will be a diffuse sea of electrons, positrons, neutrinos and
radiation suspended in nearly complete and total blackness.
-
- This U-M research study was supported by the National
Science Foundation, NASA and the U-M Department of Physics.
-
- Note: This story has been adapted from a news release
issued by University Of Michigan for journalists and other members of
the public. If you wish to quote from any part of this story, please credit
University Of Michigan as the original source. You may also wish to include
the following link in any citation: <http://www.sciencedaily.com/releases/2000/02/000218115800.htm
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