THE Sun鈥檚 nearest stellar neighbour, Proxima Centauri, may be home to a giant
planet, according to a report in this month鈥檚 Astronomical Journal (vol 115, p
345).
A team led by Al Schultz of the Space Telescope Science Institute in
Baltimore spotted an object near Proxima Centauri using the Hubble Space
Telescope. It appeared as a faint point of light close to the star, which lies
just 4.2 light years from the Sun.
Three months later, the object had moved slightly, as expected for an
orbiting companion. If it is a planet, Schultz says, it must be at least ten
times the size of Jupiter. But it could equally be a brown dwarf鈥攁 failed
star too small to shine.
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Schultz is confident that his team has ruled out other
explanations鈥攕uch as instrumental effects, or a star in the background.
This may be the first direct image of a planet beyond the Solar System. The
dozen or so extrasolar planets discovered so far have been detected indirectly
because their gravity makes their parent stars wobble. 鈥淭his is
different鈥攜ou can see it,鈥� says Schultz.
One puzzle is why other methods have failed to spot the object. A member of
Schultz鈥檚 team, Fritz Benedict of the University of Texas at Austin, has looked
for wobbles in Proxima Centauri鈥檚 motion due to a massive orbiting companion,
but has found none. Schultz suggests that the object has an extremely eccentric
orbit, spending only a little time close enough to the star to have a detectable
effect on its motion.
Planet hunter George Gatewood of the University of Pittsburgh is not
convinced, arguing that highly eccentric orbits would be very unusual in a
system like this. But he remains intrigued. 鈥淭he Proxima star is right on top of
us,鈥� he says. 鈥淚f they are right and it has a companion, I think that鈥檚
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