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Two New Planets Touted

jjswaim schrieb/wrote/a écrit:

> ... what the criteria were for excluding the possiblity
> of life on the planets in a multiple star system?


Hello Julia and List,

Two New Planets Touted (Sky& Telescope, July 1997, p. 17):

(Cambridge, MA) As April drew to a close, researchers presented evidence
for two very different planets beyond our solar system.
On April 25th, Sylvain G. Korzennik (Harvard-Smithsonian Center for
Astrophysics), Timothy M. Brown (High Altitude Observatory), and six
colleagues announced that Rho Coronae Borealis appears to be circled
every 39.6 Earth days by an unseen companion. They deduced the planet's
presence by measuring the star's back-and-forth motions for 10 months
with the 1.5-meter Whipple Observatory reflector in Arizona.
Rho Cor Bor is a 5th-magnitude Sunlike star some 54 light-years away. If
the star is as massive as our Sun (as its spectral type suggests), then
its putative planet has a mass at least 1.1 times that of Jupiter and an
orbit 0.23 astronomical unit from the star - 60% of Mercury's average
distance from our Sun.
According to Alan P. Boss (Carnegic Institution of Washington), the
discovery is significant because other so-called "hot Jupiters" are even
closer to their parent stars. Astronomers doubt that such massive
planets could form in such close quarters; instead, such planets are
believed to form farther out, then somehow spiral inward (February
issue, page 12). Rho Coronae Borealis, says Boss, may prove that the
inward migration can stop at different places in different solar
systems.

The second announcement came three days later from John R. Mattox
(Boston University) at a meeting of gamma-ray astronomers in
Williamsburg, Virginia. Maltox and his colleagues used an instrument
aboard the Compton Gamma Ray Observatory (GRO) to time clocklike blips
from Geminga, an enigmatic pulsar roughly 500 light-years from Earth. By
combining six years of GRO data with earlier satellite observations, the
team deduced a 5.1-year orbit that may be shared with a planet with at
least 1.7 times the mass of Earth.
Mattox stresses that Geminga's planet "needs to be confirmed" because
the pulsar's shifting emissions have been traced reliably for only one
cycle. They could simply reflect changes in the pulsar's internal
structure. GRO's aging detector may not be able to track Geminga much
longer. But there is another possible test: if its orbital plane
parallels our line of sight, the planet should eclipse Geminga in the
year 2000.
Neither planetary body is a likely abode for life. Rho Cor Bor's would
have scorching surface temperatures around 300° Celsius. And, according
to Aleksander Wolszczan (Pennsylvania State University), any planet
orbiting an energetic pulsar like Geminga would be showered with enough
high-energy particles to dwarf even the largest solar flare.
Furthermore, if the planet predated the supernova that spawned Geminga,
its life-sustaining atmosphere and oceans would have been destroyed by
that cataclysm.

-------- snip --------

The last passage is the important one here - namely that life (as we
understand it) in a binary system with such terrific, high-energy
particles from a pulsar is impossible.


Best wishes,

Bernd

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