Jupiter's Bigger Brother

Hi Eamonn,
This is most interesting; I remember such theorizing from my younger days. If I am not mistaken the key seems to be a theoretical planet about 1.5 – 2.0 times the mass of Jupiter, if this theoretical planet has an orbital radius of ~40 thousand AU then it roughly has an orbital period of about seven and a half million earth years, it may even be the case it might only show a displacement parallax as small as 7 arcsec over a six month period with a magnitude of +22 / +23, NO WONDER IT IS HARD TO FIND!
You also indicated the possibility of yet another planet but closer in, I guess it is not outside the realms of possibility, I mean we are detecting exoplanets around other stars, so I guess if such planets exist are relatively close by in cosmic terms then I am sure we will eventually find them.
I am theorizing that such a massive body at that distance moving through space would perturb comets within the nearer radius of the Oort cloud and thus clumping them as it were, would there be evidence of other such groupings of comets in space as a result from the wake of this theoretical planet, could such a body send comets our way into the inner solar system?
It’s interesting that you mention the 1.2m UKST in Australia, if I am not mistaken, a number of years ago the UKST was using photographic plates which covered about seven square degrees of sky, was this technology used for the search, can you give an indication of how much sky coverage was completed?
It’s also interesting that Dave mentioned IR data from satellites; do you think such an object would show up brighter in the IR, what about the older IRAS data? Could it be possible that such a massive planet could have been gravitationally captured by our solar system? Sorry for all the questions but I find it fascinating that there is now some progress on this issue.

Clear skies
Mike

Hi Mike,

Alot of questions will require detailed answers.



1. A farther Planet X: Based on the recent research by Matese such a large planet is almost on the boundary of being a small Brown Dwarf. Brown Dwarfs are very small, cool stars and because they are difficult to see, not much is known about them. If the Sun had such a companion star it would not only tell us more about Brown Dwarfs but also about the formation of the solar system. Many extra-solar planets have now been discovered with masses close to those estimated for Planet X. However, they have all been found much closer to the star than planetary formation theories would have previously predicted.

2. A closer Planet X: Periodic comet showers are associ¬ated with the passage of a planet's perihe¬lion and aphelion points through a pri¬mordial disc of comets within the Oort Cloud, which lies beyond the orbit of Neptune. According to Matese and Whitmore, the required orbital ele¬ments and mass of Planet X are consist¬ent with independently predicted values based on the residuals in the motions of Uranus and Neptune. Comets scattered directly into the zones of influence of Saturn and Jupiter can contribute to a shower whose duration is consistent with observation in less than 15 million years. This imposes a minimum planetary incli¬nation of 25°, which in turn restricts the semi-major axis to around 100 A.U. The number of showers and steady state comets are in agreement with known terrestrial crater rates. The old model of the 1990s of Planet X, could create the required density gradiant of comets near perihelion and aphelion during the life of the solar system. The inclination of Planet X’s orbit by more than 25 degrees may explain the failure of previous surveys to discover the planet as its present latitude is not likely to be near the ecliptic.

3. John Murray carried out a search using plates taken with the UK Schmidt Telescope and digitally scanned using SuperCOSMOS. The planet was expected to have characteristic parallax of 5 to 8 arcsecs based on the estimated distance from the Sun. The plates were 6 by 6 degrees which allowed a significant area of the predicted position. The search covered 42 per cent of the error ellipse around the predicted position and revealed 44 potential “planet” suspects in total, all with R-band magnitude greater than 20. The object would have been brightest in the infrared when applying the R-band filter. The “planet” suspects were close to the photometric limit of the plate which has not revealed the planet.



4. Previous old theories and searches: Predictions of the possible location of Planet X have been made, but selected searches have revealed nothing so far. Infrared Astronomy Satellite (IRAS) and Pioneer observations exist as addi¬tional sources of observational data. In addition the HST doesn’t have the parallax to determine a small shift. However, IRAS is a to low resolution telescope to show any unambiguous shift. Various astronomers have concluded that an object at a distance of 50 to 100 AU should not ex¬ceed 5 Earth masses. This would limit the visual magnitude to 15 or less. Past visual (i.e. photographic visual) searches for Planet X in the ecliptic plane have not yielded positive results. These searches included Tombaugh's search to magnitude 16 in 1961; Luu and Jewitt in 1988; and Harrington's 6-year search up until 1992 which covered Scorpius and Centaurus to magnitude 16. None of the above surveys used large, wide-field instruments. Kowal’s extensive 10¬-year survey on the Palomar 48-inch Schmidt telescope (ending in 1985) which covered 15° on either side of the ecliptic to magnitude 20.


5. However, Lykawka has a very convincing case for a Planet X within the Solar System based on the resonances of the EKB. His model is very robust and deserves a serious case for developing further. In fact, the chances of detecting the planet using Lykawka’s model are more favourable to detect in my opinion.
It will have a shift of about 1.5 arc secs, as compared to the recent Matese model that will be problematic again in discriminating shifts in the IR of 10 arc secs. Matese and Whitmore have been hobby horsing this model for the last 25 years, gradually refining the model with a improvement of comet clumping.
All their papers during that period, have suggested the planet is there, but have never worked out a search location.

On the other hand, Lykawka is at present refining the search location, this will take at least to the end of this year. The planet so far is estimated to be 10k to 14k in diameter, 80-150 AU with an inclination of around 40 degrees.

All the models make a convincing case for the potential success of a renewed search for a Planet X in our Solar System. The fact that a Planet X in our Solar System has not been found does not prove it is not there. Indeed in only removes the more unlikely theories as to its properties such as age and mass. In addition if we discover this planet X, we may have a new class of planets within our Solar System, which may have resulted partially by capture or perhaps by ejection. Planetary formation theorists may have to accommodate new classes of planetary systems; however this may come about most effectively through searching for extended planets or Brown Dwarfs within our own solar system, which then may indicate that there are other exoplanets with similar characteristics. The potential therefore is the detection of 2 planets, one considerably further out at 25k AU as compared to one at 150 AU. The farther one been huge at 3 to 4 Jupiter mass compared to the closer one 1.5 earth mass.

Eamonn A