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

[Sterling K. Webb]

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.