A Gas Giant in the Oort Cloud?

by Paul Gilster on February 21, 2011

Of all the interesting targets the WISE (Wide-Field Infrared Explorer) mission might find, I’ve focused primarily on two in Centauri Dreams: A small star, doubtless a brown dwarf, that might be found closer to us than the Alpha Centauri trio, and a large planet out in the Oort Cloud that might be disturbing cometary orbits. That latter scenario turned up again last March in Finding the Real Planet X, when we looked at various theories about large objects in the outer system, including the thinking of John Matese and Daniel Whitmire (University of Louisiana at Lafayette).

Parameters of a Perturber

Matese has studied the possibility of small stars near our Sun for two decades, but his view now, as revealed in a paper just published in Icarus, is that an object three to five times larger than Jupiter may be the perturber we’re looking for. Matese and Whitmire’s paper on the matter has been available as a preprint since April, but its publication in Icarus has caught the eye of the press, as in this story in The Independent. Think of all the time Percival Lowell devoted to finding a large ‘Planet X’ that wasn’t there (although the detection of Pluto did come out of the search), while a truly massive Planet X at a far greater distance may now turn up in WISE data.

And the Planet X we’re talking about is not ‘Nemesis’ — that would be the name for the small star once considered a possibility as a binary companion to the Sun. Matese and Whitmire prefer ‘Tyche,’ the good sister of Nemesis in mythology, as the name for the gas giant they hope to find in WISE’s data. We’ll have to wait a bit to find out, but not all that long. WISE, whose transmitter has now been turned off, has completed its principal and extended missions and is in hibernation as of early February. The first release, covering 57 percent of the data gathered, will be in April, with the full dataset becoming available in 2012. Matese and Whitmire have calculated that the object should have a temperature of roughly 200 Kelvin, and WISE should be able to see it.

Tyche sounds like a gas giant, according to Whitmire, but even assuming it to be so, we won’t know if it qualifies as a ‘ninth planet’ of our system until the International Astronomical Union considers the matter. After all, we live in a world where Pluto lost its status due to reconsideration of small icy worlds, and it may be that a massive gaseous world out in the Oort Cloud at 15,000 AU would raise questions about its origin. Is it likely that such a planet would have formed around another star, and if so, shouldn’t there be a new, separate designation?

The Planet and the Tides

We’ll see what happens when and if Tyche is discovered. Beyond the possibility of a new planet, the paper on this work becomes absorbing in its study of the effects of the galactic tide (drawing objects toward the center of the galaxy) in pulling comets out of the Oort Cloud. In their analysis of earlier work on the matter, the authors conclude, “…the data are of sufficiently high quality to unambiguously demonstrate the dominance of the galactic tide in making comets discernable at the present epoch.” Where Tyche fits into that picture is that a certain percentage of long-period comets evidently enter the Solar System at an angle that the galactic tide theory cannot explain, offering evidence of perturbation by our unseen companion.

From the paper (here I’m quoting the preprint, as I don’t yet have the Icarus paper. Be aware that this section may have been amended in the final draft):

We have described how the dynamics of a dominant galactic tidal interaction, weakly aided by an impulsive perturbation, predicts specific properties for observed distributions of the galactic orbital elements of outer Oort cloud comets. These subtle predictions have been found to be manifest in high-quality observational data at statistically significant levels, suggesting that the observed OOC comet population contains an ≈ 20% impulsively produced excess. The extent of the enhanced arc is inconsistent with a weak stellar impulse, but is consistent with a Jovian mass solar companion orbiting in the OOC.

Not only that, but such a body would have roiled the system enough to produce some of the stranger things we’ve found recently:

A putative companion with these properties may also be capable of producing detached Kuiper Belt objects such as Sedna and has been given the name Tyche. Tyche could have significantly depleted the inner Oort cloud over the solar system lifetime requiring a corresponding increase in the inferred primordial Oort cloud population. A substantive difficulty with the Tyche conjecture is the absence of a corresponding excess in the presumed IOC daughter population.

In other words, the Tyche work can explain the behavior of comets from the outer Oort Cloud, but it has trouble with the inner Oort (IOC). Even as we go to work on the dynamics of cometary motion in that region, we should know soon whether this analysis is purely theoretical or has planetary implications. The Independent says Matese and Whitmire think WISE will find Tyche in short order, quoting the latter: “If it does, John and I will be doing cartwheels. And that’s not easy at our age.”

The paper is Matese and Whitmire, “Persistent evidence of a jovian mass solar companion in the Oort cloud,” Icarus Vol. 211, Issue 2, pp. 926-938 (abstract / preprint).

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{ 18 comments }

Alex Tolley February 21, 2011 at 11:01

While Tyche is about 10x too close to be Nemesis, I wonder if some sort of synchrony might offer the 62my period that might explain the periodic extinction events suggested by Richard Muller?

Randy McDonald February 21, 2011 at 12:40

Do either the core accretion or disk instability models of planetary formation suggest that such a massive planet could form so far out from Sol, in the etiolated reaches of the Oort cloud? If it exists, Tyche might have formed like a star, a stillborn partner, indicating the multiple pathways towards a high-mass sub-stellar object I suppose.

Steven Colyer February 21, 2011 at 14:25

Alternatively, it may be that the Kuiper belt and the Oort Cloud are massive enough in their own right to send the comets into our inner Solar system.

Much skepticism should remain until, as you say, WISE provides better data.

Adam February 21, 2011 at 20:51

A gas giant that’s 200 K warm would heat a nearby moon, at four times its radius, to 100 K at the sub-jovian point on the moon. A sufficiently dense atmosphere would be able to sustain liquid oceans under that NIR illumination, though the formation environment of such a close moon might preclude atmospheric retention. Perhaps formation further out and migration inwards might allow such a moon. A dark, warmer Titan, with minimal UV to produce the anti-greenhouse effect of Titan’s smog.

Back in the 1970s Titan’s atmosphere was a big unknown. Some radiometry measurements indicated a warm surface as ‘hot’ as 200 K, necessitating a massive greenhouse effect to sustain it – a nitrogen atmosphere of ~21 bar pressure was seriously considered. Measurements by Arecibo, just prior to “Voyager”, dropped the surface temp to just ~100 K and just ~2 bar pressure, not too far off the observed ~93.6 K and 1.46 bar. The ‘hot’ layer was actually the stratosphere, which averages ~170 K, while the antigreenhouse drops the top of the troposphere to just ~70 K. The alternative thin atmosphere model had a wisp of methane in equilibrium with an ~80 K surface, and Arecibo and “Voyager” decisively confirmed the “thick”, but not super-thick, model.

The lesson being that we might be surprised, but not super-surprised?

Bobby Joe Kepler February 21, 2011 at 21:32

A couple colleagues have sent me some very interesting articles and graphics about this Techne critter. Apparently NASA is going to unfold its info campaign soon. Depending on its rotational velocity and its mass I don’t see why it couldn’t be sweeping in stuff from the Oort cloud, as opposed to flinging things into the inner Solar System. One estimate I saw put the mass at 5 times greater than Jupiter’s. Even Jupiter seems to do some very weird stuff with mainly hydrogen under super pressure, just not fusing the atoms. So why couldn’t this Tychne be a small star in the process of lighting up, so to speak?

Johnny Nielsen February 22, 2011 at 4:06

@Bobby Joe
As far as we know there really isn’t enough mass, let alone gas, in the entire Oort structure, to build up anything coming even close to the point where even simple proton-proton fusion can occur. There just isn’t enough potential density for the particles to be able to reach the Gamow window.
So the only energy radiating from a hypothetical super Jupiter situated in the Oort cloud, would be residual from initial contraction and subsequent bombardment.
Also, I’m not sure if I misunderstand you, but NASA has no info campaign coming up on Tyche. The first 14 weeks of the WISE data will be released to the public in April and the rest of it sometime in 2012. That’s about the extend of NASA’s involvement in the Tyche debacle.

@Randy
Very very interesting question. If we assume that the Oort cloud is proven beyond any reasonable doubt to even exist, what would be the mass, position and composition required to create something like Tyche (well, or Nemesis for that matter), while still retaining all the characteristics of the parts of the solar system we know for a fact exists?
It would be fun to run the modelling software on that, as well as take into account what effect pertubations from Sol’s neighbourhood would have. Astronomers… Go and get computer time for that project please :)

bill February 22, 2011 at 4:33

could the pluto space probe fly by it ?

kzb February 22, 2011 at 8:52

@Bobby Joe Kepler: please can you tell us what is your source for the statement, “Apparently NASA is going to unfold its info campaign soon.”
Can you fill in a few details ?

Personally I think Matese and Whitmire could be “positioning” themselves just on the off-chance that something is found in the WISE data. It could earn them a footnote in future text books if they had “predicted” this planet before it was discovered.

I also think we should keep an open mind. It does not have to have been formed along with the rest of the solar system. Planetary Mass Objects can form independently in star-forming regions, and planets can be stolen or ejected from their natal systems.

Bill B. February 22, 2011 at 12:23

If WISE finds ‘Tyche’ out there at 15,000 AU, it would make a very interesting probe mission that could be a sort of pre-cursor to true interstellar probes. A probe could be built with Tyche as a primary mission, and then it could be assigned an additional target maybe another OOT object or a brown dwarf that might be discovered within a couple of light years away.

jkittlejr February 22, 2011 at 12:57

I have this feeling that we have not seen the last of WISE. A functional telescope is a hard thing to wet aside. Given the probable delays in WFIRST, if the Wise Data is anywhere near as rich as I believe it to be, there will be interest in turning this thing back on next year. It would be very interesting to see the evolution of science and having a year wait will allow new objects to come into view or capture the motion of objects like a theoretical Oort cloud giant planet, or even a nearby ( small) brown dwarf.
You realize of course that a major geologic event on an an earth-sized planet ( like a big volcanic eruption) might be visible in the outer Kuiper belt.. if such a planet existed and has been missed because of low abedo.

Ron S February 22, 2011 at 16:00

bill: “could the pluto space probe fly by it ?”

Unlikely. There are pre-requisites that would have to be met:
- Tyche exists and is found.
- Determination of Tyche’s exact position.
- That position would have to fall within the small range of trajectories that the probe could conceivably achieve. This is constrained by the small amount of fuel it’ll have and the degree to which a gravitational slingshot maneuver would interfere with its primary mission.

As I understand it, NASA is still considering alternatives for where to head off after Pluto, but the currently available choices of what they can reach aren’t especially interesting.

Paul Gilster February 22, 2011 at 16:34

Bear in mind too that New Horizons will spend six years getting to Pluto (roughly 40 AU). If Tyche exists, the thinking of Matese and Whitmire is that it is at about 15,000 AU — farther than Proxima Centauri from Centauri A and B. In other words, it would be a long, long journey even if New Horizons by chance happened to be pointed at it.

Adam February 22, 2011 at 19:08

Tyche would be a great First Interstellar Mission target IMO. Assuming it exists, that is. If it proves bigger and warmer than expected, that’s even more reason to go.

kzb February 23, 2011 at 9:02

Interesting paper on WISE capabilities (link below). It does not specifically mention outer planet spotting, but it does make it clear that WISE is the best thing so far at infra red surveys by a considerable margin.

jkittlejr: I notice on the WISE website that the satellite was turned off on 17-Feb, but do they say it is mothballed for any future use.

http://arxiv.org/abs/1008.0031

Tobias Holbrook February 24, 2011 at 17:21

As Karl Schroeder pointed out… how much power would be available from such a bodies magnetic field? Couple this with tidal heating and the possibility of tapping the residual heat from formation (concentrating the IR, planting aerostats in it’s atmosphere to mine the thermal energy), and we could build an interstellar colony there…

It would only be 2.74 light months away, if it exists 15,000 AU away. Given fast, 0.4-0.6c beamriding spacecraft, and one could envision interstellar trade occuring between Terra and Her colony(ies). If there turns out to be more than one… what are the possibilities of a multitude of such bodies existing within several light months of Terra?

kzb February 25, 2011 at 9:00

Tobias Holbrook: but who’d want to spend their lives in continual darkness on a moon? Even when you step outside your colony in your spacesuit, you’d need a torch just to see where you’re putting your feet. Living in the colony would be much like living on a spaceship.

The possiblity of a multitude of such objects is of course very interesting. If it turns out there are PMOs and brown dwarfs every few light months it could make the stepping stones concept viable, IF people were willing to live that way.

Trouble is, I think that is only an extreme possibility going on current information. If you look at the paper linked to above, the statement IS made that there are probably 1 to 2 brown dwarfs (of mass 1 to 80 Jupiters) for every visible star. One line in their Table 2 gives a density probability of 1.82 within 1.3 parsecs, which I take to mean there is a greater than evens chance there is one PMO/BD nearer than Alpha Cent, and there might even be 2 or 3.

However that seems to be the most optimistic view of the possibilities. I have another paper here about the Spitzer Deep Survey of 10 square degrees of sky. The central expectation value for BD detection in that survey was 55, but they only found eight. They then go on to explain how the BD atmosphere models need modifying, and that could bring their detection rate up to expectations.

Most recent papers with evidence from star-forming regions have the stellar mass function peaking around one-quarter of the solar mass, and turning down at lower masses. This would mean that BD’s are less common than visible stars.

So we are presented with a confused picture at the moment, but I don’t see anyone is predicting that PMO/BDs are only a few light months apart.

Hopefully the issue will be resolved when people have had chance to work on the WISE data.

Tobias Holbrook February 26, 2011 at 13:42

kzb,

The same people, I imagine, who would want to colonize the outer solar system would want to colonize a brown dwarf/superjovian. There’s plenty of light out there from the planet itself – infrared, maybe, but good enough for photosynthesis. Coupled with bioluminescence…

I imagine it’s more likely that there are rogue Neptunes than rogue Jupiters – especially given the paucity of hydrogen at those distances. However, given the thermal energy inherent in such a body, cooupled with tidal heating and classic radioactive decay, there should be quite a bit of energy available out there. Even if we only find lily pads that are more like Neptune than Jupiter, there’s still the potential for viable colonies to be established. Unfortunately, such objects wouldn’t be detected by WISE… the possiblity of a rogue Neptune every few light months doesn’t seem excessively unlikely, given chaotic planetary formation, and the potential for ongoing planetary formation in the Oort cloud (has anyone looked at this?).

I’m still holding out hope for a Brown Dwarf or Superjovian, though, given the much more plentiful energy resources and bigger moons…

kzb March 7, 2011 at 14:15

Tobias
According to the WISE website, a Neptune-sized body should be detectable to 2000AU, if I remember correctly.

I don’t think you can assume that rogue Neptunes are more common than rogue Jupiters. There are two possible mechanisms how rogue planets can come into being by current ideas.

The first is by the stellar formation mechanism. Direct observations of young star clusters show that the mass distribution extends right down into the planetary mass area. However, the frequency distribution decreases with decreasing mass below about one-quarter the solar mass. Also there could be a lower mass cut-off for formation by this mechanism. So Jupiters should be MORE common than Neptunes; in fact Neptunes might not be possible at all.

The second is by planetary ejection, and this could well lead to more Neptunes, however from the papers I have seen there can also be a lot of Jupiters ejected.

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