The idea that there is a tenth planet or other body beyond the orbit of Pluto is becoming popular among astronomers. At a conference held at NASA's Ames Research Center in June, 1982, a number of researchers discussed the growing evidence that something is out there: perhaps a planet, perhaps the remnant of a burned-out white dwarf or neutron star that was (is) a binary companion to the Sun, perhaps even a black hole.[1]

The evidence for such a body comes from the fact that the gravitational forces among the Sun and known planets cannot account fully for the observed orbital motions of the planets, particularly Uranus and Neptune, which show tiny unexplained deviations or perturbations from their predicted orbits. The same situation existed prior to the discovery of Pluto, and the belief that an unknown planet was causing the perturbations was in fact the motivation for the search that led to Pluto's discovery in 1930. Nowadays it is clear that Pluto was found for the wrong reasons; its mass is too low to produce the observed effects. Hence the new interest in finding a body out beyond Pluto.

Until more is known, it is easy to speculate about what could be out there. Astronomers at the NASA-Ames conference suggested a planet the size of Uranus at a distance of about 100 A.U. [1 A.U. = 93,000,000 miles, the distance from the Earth to the Sun] from the Sun, or a burned-out star at a distance of about 500 A.U., or a black hole (10 solar masses) at a distance of about 1000 A.U. Others have argued that the available evidence implies a body of 2 to 5 Earth masses, lying out of the plane of the ecliptic.[2]

From a Velikovskian perspective, there are also other possibilities. One is simply the idea that the perturbations could be minor effects of electrical or magnetic forces superimposed on the gravitational forces that are mainly responsible for the orbits. The source of such electrical or magnetic forces need not be a solid body but could be the sort of large-scale fields in space that Ralph Juergens envisioned.[3]

Another rather speculative possibility is that an unknown body does exist beyond the orbit of Pluto, that is it on a highly elliptical orbit with its perihelion well inside the orbit of Pluto, and that it participated in at least one of the planetary interactions described by Velikovsky.[4] For example, the unknown body could have passed near the orbits of Jupiter and Saturn several thousand years ago and could have participated in the birth of Venus. Or it could have passed through the inner solar system in the fifteenth century B.C. and have been the cause or catalyst of some of the Venus-Earth interactions.

To conjecture about the details of any such interactions seems fruitless without more information. However, there are some things that can be said about the range of possible orbits that would allow the unknown body to be: (1) close enough to engage the known planets in a Velikovskian interaction within the past several thousand years, (2) close enough to perturb the known planets at the present time, and (3) far enough away to remain unnoticed in the interim. Much depends on the mass of the unknown body but, since it left behind a reasonably intact planetary system, it must have been much smaller than the Sun.

Suppose we assume the unknown body to be no larger than Uranus and to be following an elliptical orbit that meets the above conditions. Its orbital period must be at least 3500 years, so its semimajor axis must be at least 230 A.U. If it is now close enough to perturb the outer planets, it cannot be more than about 100 A.U. from the Sun, which means that it cannot be moving away from the Sun. It must already have passed aphelion and be heading back toward the inner solar system. As can be seen from Table I [below], all of the applicable orbits have rather similar properties within 100 A.U. of the Sun, regardless of whether the orbital period is 3500 years or 14,000 years. If there is indeed an unknown body on such an orbit, it is heading toward the inner solar system at roughly 1 A.U./year and will reach perihelion in a century or less.

The idea that the body now perturbing the outer planets has a highly elliptical orbit is of course pure speculation; it is generally consistent with but not necessarily a consequence of Velikovsky's theory. Within a few years, the nature of the unknown body may become much clearer; astronomers are optimistic that its effect on the trajectories of Pioneer 10 and Pioneer 11 will be measurable as the two space probes move out past Pluto's orbit and will indicate the mass and location of the unknown body, even if it cannot be located visually. In the meantime, one can wonder whether the overall effect of a body returning to wreak interplanetary havoc in the solar system would be entirely bad. It could kill us all, though reports of previous encounters imply that some of us survived. Could it also make us realize the foolishness of our petty squabbles, over which we threaten to kill ourselves?

Table I : Representative Elliptical Orbits

* True anomaly is a planet's heliocentric longitude from perihelion.

For a planet moving inward from aphelion to perihelion,

both the true anomaly and the radial velocity would be negative.

References

1. "Something lurking beyond the planets", New Scientist 94, 829 (24 June 1982). See also "Mysterious Planet X", Science Digest (Nov. 1982), p. 42.

2. "Search for the Tenth Planet", Science Digest (Dec. 1981), p. 17.

3. R.E. Juergens, "Electric Discharge as the Source of Solar Radiant Energy" (KRONOS VIII:1, pp. 3-14, and KRONOS VIII:2, pp. 47-62), and other papers cited therein.

4. Cf. R.S. Harrington and T.C. Van Flandern, "The Satellites of Neptune and the Origin of Pluto", KRONOS V:2, pp. 48-56, for discussion of a non-Velikovskian orbital interaction involving the outer planets.