[meteorite-list] Newfound Planet Has Earth-Like Orbit

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun, 5 Aug 2007 16:41:14 -0500
Message-ID: <006801c7d7a9$59ad8f60$ac2ee146_at_ATARIENGINE>

Newfound Planet Has Earth-Like Orbit

http://www.space.com/scienceastronomy/070802_redgiant_planet.html


A planet outside our solar system with a year
roughly equal to Earth's has been discovered
around a dying, red giant star.

Only about 10 red giant stars are known to
harbor planets; the new solar system is among
the most distant of these.

Our sun will become a red giant in a few billion
years, likely vaporizing Earth.

The finding, to be detailed in the November issue
of Astrophysical Journal, was made by a team led
by Penn State astronomer Alex Wolszczan, who in
1992 discovered the first planets outside our solar
system around a deadly, radiation-spewing star.

A bloated parent

The new planet, spotted using the Hobby-Eberly
Telescope at the McDonald Observatory in West
Texas, circles its bloated parent star every 360 days
and is located about 300 light-years away, in the
constellation Perseus.

The red giant star is twice as massive and about
10 times larger than the sun. Its planet is about
the size of Jupiter or larger and was discovered
using the so-called wobble technique, in which
astronomers look for slight wiggles in a star's
motion created by the gravitational tug of orbiting
planets.

The discovery could help astronomers understand
what will happen to our sun's brood of planets
when it exhausts its store of hydrogen fuel and its
outer envelope begins to swell. When that happens
in an estimated 5 billion years, our sun will be so
big that it will engulf the inner planets and most likely
Earth. But long before that happens, life on our planet
will have perished and its seas will have boiled away.

"Our sun probably will make the Earth uninhabitable
in about 2 billion years because it will get hotter and
hotter as it evolves on its way to becoming a red giant,"
Wolszczan said.

Up from the ashes

Our sun's slow death will throw the orbits of the
remaining planets out of whack. Some planets
might collide with one another, and new ones could
form from the resulting debris. And while all the
organisms on Earth will have disappeared by that time,
life could arise anew on other worlds in our solar
system. Scientists speculate that there is more than
enough time during a star's giant phase for life to
evolve again.

As our sun expands, the spherical boundary within
which liquid water can exist, called the habitable
zone, will also expand, so that now frigid planets
and moons in our solar system could become
warm enough for life in the future.

"In our solar system, places like Europa-a satellite
of Jupiter that now is covered by a thick layer of
water ice-might warm up enough to support life
for more than a billion years or so," Wolszczan said.

After the red giant phase, a star enters the final
stage of evolution. It casts off its outer gas layers,
leaving behind a compact stellar corpse called a
white dwarf, which will smolder until all its
remaining heat is radiated away.
Received on Sun 05 Aug 2007 05:41:14 PM PDT