Search for Planet X
Harrington, Robert S.

The observation of the region of the sky in which it is believed Planet X should now be, based on perturbations observed in the motions of Uranus and Neptune, was determined, and there was no reason to update that determination. A limited area of that region was photographed, and that will be continued. A given area is photographed with the twin 20 cm astrograph in New Zealand on two successive nights near the time that area is in opposition, and these plates are blinked in Washington to identify anything that has moved. The predicted region is in the south, which requires observations from a southern station, and it is in opposition in the April to June period, which means observations have not yet started for the year. Blinking will be done as soon as the plates are received in Washington.

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The location of Planet X
Harrington, Robert S.

Observed positions of Uranus and Neptune along with residuals in right ascension and declination are used to constrain the location of a postulated tenth planet. The residuals are converted into residuals in ecliptic longitude and latitude. The results are then combined into seasonal normal points, producing average geocentric residuals spaced slightly more than a year apart that are assumed to represent the equivalent heliocentric average residuals for the observed oppositions. Such a planet is found to most likely reside in the region of Scorpius, with considerably less likelihood that it is in Taurus.

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A mathematical search for Planet X
Powell, C.

It is proposed that the systematic residuals in the positions of Uranus and Neptune may be due to an unknown planet: Planet X. Using the weighted-least-squares method, the orbit and mass of Planet X were computed from the residuals of Uranus. It is concluded that, if it exists, Planet X will be the tenth planet. However, it may not be the tenth from the sun since the computed semimajor axis is a little less than Pluto's. Planet X's perihelion, like Pluto's, is inside the orbit of Neptune.

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Mass and orbit estimation of Planet X via a family of comets
Neuhaeuser, R.; Feitzinger, J. V.

Characteristics of Planet X are developed by examining the aphelion distances and orbital parameters of comets that are assumed to beinfluenced by the unobserved planet. Planet X's semimajor axis and orbital eccentricity are found by, respectively, averaging the apheliondistances and studying the orbits of certain transplutonic comets. The orbital inclination is also estimated based on the assumed role of Planet Xin directing quasi-periodic comet showers toward the inner solar system. The mass of the planet is calculated by extrapolating the densitydistribution of the primordial solar nebula. A list of assumptions including the cause of planetary perturbations is used to describe the actual location of Planet X including declination and ecliptic longitude as well as the apparent brightness.

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Planet X - The current status
Seidelmann, P. K.; Harrington, R. S.

Theoretical models of solar-system dynamics which predict the existence of a 10th planet (planet X) are surveyed and compared with recent observations. The history of the discoveries of Neptune and Pluto on the basis of discrepancies in the orbit of Uranus is recalled in detail, and the persistence of such discrepancies in 9-planet computations is considered. Particular attention is given to ongoing efforts to compute the current position of planet X, and to ground-based and space-based (IRAS and Pioneer) searches. Diagrams and graphs are provided.

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There are over 500 abstracts relating to perturbations in the outer planets caused by the hypothetical planet x. Click on the link below to view the entire set of abtracts.

Full Listing of Harvard Abstracts on the topic of Planet X