Exoplanets: Why There
May Be a Lot More Than We Currently Know
The
relatively recent discovery of exoplanets in other star systems has been one of
the most exciting developments in early 21st century science that has
strengthened the traditional sci fi interest in the possible existence of
non-human intelligent life. So far, the
majority of exoplanets identified have belonged to a class of celestial bodies
that includes “gas giants” such as Jupiter and Saturn. Only a few years ago were the first planets
found that could have structures similar to Earth, thus presumably more likely
to harbor the conditions for life resembling our own. However, based on our local observations on
this planet, such bodies would have to occupy a habitable zone, neither too
close nor too far from their stars, so as to sustain liquid water and temperatures
conducive to Earth-based life. Given
these restrictions, astronomers have not yet found an ideal candidate, a “Goldilocks
Planet”or twin to Earth that would give a very high probability of life, much
less intelligent life. A good summary of
the current state of the search is Dr. Sten Ostenwald’s article in the
Huffington Post, “Exoplanets: The New Age in Planetary Science” (3/10/14).
Results
in our so-far-limited scrutiny of the Milky Way Galaxy’s planets therefore lead
us back to the nagging question of the Fermi Paradox: if intelligent life is
out there, why haven’t we seen any of it?
A
positive answer to this conundrum may be closer than we realize if we look at our
own prejudices in analyzing distant star systems. We humans have been lucky, but also unlucky
perhaps, in that our own solar system is so neatly arranged. The arrangement is a disk. Around our sun, the planets fall into a neat,
nearly circular array, all lined up in roughly the same plane. Only about six degrees of variance exist
between the orbits of Earth and its neighbors, a serendipitous fact that helped
humans discover some facts about near space long before we could begin to go
there. The existence of such an ecliptic
of planets is something we more or less take for granted.
Certainly,
the ecliptical view of things has influenced our observations of exoplanets so
far. This is because we can determine
their existence not by sight, but by recording variances in the radiation
reaching us from their stars as the planets pass in front of them relative to
Earth, creating in effect a mini-eclipse at a tremendous range, detectable by
only the finest instruments.
Another
question imposes itself: what if there are exoplanets out there that are not
orbiting their stars in such a way as to come between the star and Earth? After all, we have no way of proving that all
stars have ecliptics similar to our sun.
There may conceivably be stars where planetary orbits do not form a flat
plane at all. And even if they do, as
some theories about the formation of solar systems suggest, why would an exo-ecliptic
necessarily have to be co-planar to the direction of Earth? It is true that our galaxy’s spiral structure
might tend toward a “universal” coplanar coincidence, but so far there is
nothing to suggest that it would be as uniform as that of our own solar
system. In addition, many stars exist in
clusters or other environments that might exert gravitational influences that
would override coplanarity.
The
bottom line is that any given star might have perfectly well-developed planets
similar to Earth that have not been discovered, and may not be for a long time,
simply because their orbital angles do not allow us to observe their existence. How many undetected Earth-like planets may
lie out there? It is a problem to be
considered no doubt by the mathematics of symmetry until we can refine our
methods of observation. Several sci fi
films have jumped ahead to posit the existence of an Earth twin within our
solar system, orbiting the sun exactly opposite Earth so as to be
undetectable. Given the fluctuations in
Earth’s own orbit, this kind of extreme symmetry would be most unlikely. The films that have featured it, such as “Gamera
versus Guiron,” have been filled with so many more facetious elements that the
possibility was not seriously considered.
This
should not stop us from investigating the likelihood of actual “hidden Earths”
in other star systems, since they may only be hidden by our own angle of
vision. We can never exclude the
existence of the strange, the unheimlich,
until we are a bit more positive about the exact nature of our current
planetary Heimat.
