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.