QUESTION:
We want to know what are some of the similarities between earth and the new 
found planet near 51 pegasus, and how can you tell the differences?

ANSWER from Tom McMahon onNovember 10, 1995:
The planet orbiting 51 Pegasi is believed to be roughly the same size and
composition as Jupiter, that is a gaseous planet with no solid surface.
This means that the planet would be approximately 11 times larger than
the earth.

The 51 Pegasi planet was indirectly detected. It was not actually seen nor
was any light detected from the planet. The astronomers found the planet
by detecting a wobble in the motion of the star it orbits. As the planet moves
around 51 Pegasi it pulls on the star moving it ever so slightly. The larger
the wobble, the larger the planet. The astronomers made a calculation using
thier observations and determined the approximate "mass" of the planet.

The most interesting aspect of this discovery is the planet orbits the star
at 1/20th an astronomical unit. An astronomical unit is defined as the mean
distance between the sun and earth. Astronomers did not believe that a
Jupiter-type planet could suvive an orbit that close to a star.

__________________________________________________________
Tom McMahon
University of Chicago
Yerkes Observatory