Undreamed Shores - Ocean Worlds: The Story of Seas on Earth and Other Planets - page 246

matter of speculation, almost up to the present day. Our own solar
system, with its inner rocky planets—only one of which is adorned
with surface oceans of liquid water—and its outer gas and ice giants,
with their stable, near-circular orbits, was long the only available
model of how a planetary system forms. Is our solar system the
norm—or a rarity? No one knew.
The problem is that stars are so bright and large and far away, and
planets within their glare are so small and dim. Until recently, even
the best telescope could not distinguish them. It has taken almost
superhuman levels of skill, ingenuity, and patience to separate the tiny
signals of planets from those of their parent stars. Almost yesterday,
it seems, this was first achieved. Now it is as if a dam has burst, and
astronomers are deluged with ever-increasing reports of new exo-
planets (extra-solar planets). The universe has become, almost over-
night, a much more crowded and various place: one which is
downright weirder than even science fiction writers had imagined. Fur-
thermore, some of these planets are clearly water-bearing worlds.
The Planets Beyond
The first detection of a planet beyond our solar system came not from
around a normal or 'main sequence' star, but from around a pulsar.
Pulsars are rapidly rotating neutron stars (the orbital period can be
much less than a second), which are the shrunken and hyper-dense
remnants of a star after it has become a supernova. Pulsars emit nar-
row beams of electromagnetic radiation that, on sweeping round to
shine on Earth, produce pulses of radiation so regular that they were
initially thought to be signals from an alien intelligence. Hence the
first pulsar was, only partly jokingly, designated as LGM-1, with LGM
standing for 'little green men'. The signal is so regular that any tiny
deviations in it can be used to infer the presence of planetary bodies
orbiting around the pulsar.