No True Jupiters Detected
So far, we have not
detected any true Jupiters,
planets the size of Jupiter orbiting with periods of 10 or 20 years. This does not
mean that such systems do not exit. It
does not mean that the configuration
of our solar system is unique, with the terrestrial planets huddled in close to
the parent star, and the giant planets patrolling the outskirts, warding off
incoming intruders such as asteroids or comets that might be instruments of
mass extinction. No, such a conclusion
is premature, because we have so far barely achieved the Doppler precision that
is needed to detect a true Jupiter, and with few exceptions the observations do
not yet cover long enough time spans.
Both these shortcomings are being addressed. New and better instruments and techniques are being developed,
and if the telescope time allocation committees continue to be wise, we will
gradually accumulate enough additional data with sufficient time coverage to
detect true Jupiters.
The fraction of solar-type stars with discovered planets is still
rather low, just a few percent at most.
But, this could prove to be just the tip of the iceberg. The Doppler technique is picking up the
easiest planets first, the ones that are the most massive and/or have the
shortest orbital periods. As the
Doppler precision improves and the time coverage grows longer, I am confident
that we will find more planets, ones with smaller masses and wider orbits.
Contributed by: Dr. <!g>David Latham