Here Be Dragons

HERE BE DRAGONS
pounds present in the star's outer layers. It was the collective shift of
all these bands toward longer or shorter wavelengths that Queloz and
Mayor set out to measure. They did this by comparing the star's absorption
bands with the absorption bands in the light coming from a
lamp, which obviously were not Doppler shifted.
Several other astronomers had been using the radial velocity approach
for several years before Queloz and Mayor commenced their
observations. These others included two Canadians, Bruce Campbell
and Gordon Walker of the Dominion Astronomical Observatory in
Victoria, as well as two astronomers at San Francisco State University,
Geoff Marcy and Paul Butler (Butler is now at the Anglo-Australian
Observatory in Sydney). Aside from a couple of false alarms, none of
these scientists had succeeded in detecting any planets. What Queloz
and Mayor had going for them, however, was a sophisticated piece of
analytical software that very rapidly calculated the Doppler shift of the
source while the star was still under observation. Marcy and Butler's
spectra, on the other hand, had to be processed off-line, and in fact
they had accumulated several years' worth of unanalyzed spectra
when the Swiss researchers began their observations.
Queloz and Mayor chose about 125 stars to study. They had masses
similar to that of the Sun (so-called G stars) or slightly lower (K stars)
Planets of Sun-like stars are often considered the best candidates for
harboring life, so we ask Queloz whether the quest for life was a factor
behind their choice of targets. He denies it. "They're just the easiest
stars to study," he says. "The lower-mass stars are less bright, and the
higher-mass stars don't have enough absorption bands to study."
They set up their equipment at the Observatoire de Haute-
Provence, just outside the medieval town of Forcalquier in the French
Alps. Forcalquier's Romanesque Church of Notre Dame dates back to
the era when Scholastic philosophers attempted to solve the problem
of "other worlds" by the power of thought alone. Queloz and Mayor resolved
the problem empirically in July 1995, when they detected a
large planet circling a star called "51 Pegasi" (usually abbreviated to "51
Peg"). It is the fifty-first in a list of stars in the constellation Pegasus.
Queloz and Mayor had actually first noticed the variation in the radial
velocity of 51 Peg six months earlier. But the data were so unexpected
that they hesitated to believe them. For 51 Peg was moving to
and fro with a periodicity of only 4 days, and yet the amplitude of the
velocity change demanded a planet at least half the mass of Jupiter. If
the data were real, it meant that a Jupiter-like planet was orbiting its
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