"surprise discovery" in the outer Solar System Options

[Mongo]

I suppose that this can go in this thread, although it might deserve its own thread.

Extreme trans-Neptunian objects and the Kozai mechanism: signaling the presence of trans-Plutonian planets?

The existence of an outer planet beyond Pluto has been a matter of debate for decades and the recent discovery of 2012 VP113 has just revived the interest for this controversial topic. This Sedna-like object has the most distant perihelion of any known minor planet and the value of its argument of perihelion is close to 0 degrees. This property appears to be shared by almost all known asteroids with semimajor axis greater than 150 au and perihelion greater than 30 au (the extreme trans-Neptunian objects or ETNOs), and this fact has been interpreted as evidence for the existence of a super-Earth at 250 au. In this scenario, a population of stable asteroids may be shepherded by a distant, undiscovered planet larger than the Earth that keeps the value of their argument of perihelion librating around 0 degrees as a result of the Kozai mechanism. Here, we study the visibility of these ETNOs and confirm that the observed excess of objects reaching perihelion near the ascending node cannot be explained in terms of any observational biases. This excess must be a true feature of this population and its possible origin is explored in the framework of the Kozai effect. The analysis of several possible scenarios strongly suggest that at least two trans-Plutonian planets must exist.

6 DISCUSSION

Our analysis of the trends observed in Fig. 3 suggests that a massive perturber may be present at nearly 200 au, in addition to the body proposed by Trujillo & Sheppard (2014). The hypothetical object at nearly 200 au could also be in near resonance (3:2) with the one at nearly 250 au (e.g. if one is at 202 au and the other at 265 au, it is almost exactly 3:2). Any unseen planets present in that region must affect the dynamics of TNOs and comets alike. In this scenario, the aphelia, Q = a(1 + e), of TNOs and comets (moving in eccentric orbits) may serve as tracers of the architecture of the entire trans-Plutonian region.

7 CONCLUSIONS

In this Letter, we have re-examined the clustering in w found by Trujillo & Sheppard (2014) for ETNOs using a Monte Carlo approach. We confirm that their finding is not a statistical coincidence and it cannot be explained as a result of observational bias. Besides, (90377) Sedna and 2007 TG422 are very clear outliers in semimajor axis. We confirm that their presence may signal the existence of a very large population of similar objects. A number of additional trends have been identified here for the first time:

• Observing from the Earth, only ETNOs reaching perihelion at || <24◦ are accessible.
• Besides clustering around w = 0◦, additional clustering in inclination around 20◦ is observed.
• Asteroids 2003 HB57, 2005 RH52 and 2010 VZ98 all have similar orbits, and their mean longitudes differ by almost 120◦. They may be trapped in a 3:2 resonance with an unseen perturber with semimajor axis in the range 195–215 au.
• The orbits of 82158 and 2002 GB32 are very similar. They could be co-orbital to the putative massive object at 195–215 au.
• The study of the distribution in aphelia of TNOs and comets shows a relative deficiency of objects with w close to 0◦ or 180◦ among those with aphelia in the range 200-260 au. The difference is only marginally significant (2 sigma), though. Gaps are observed at ~205 au and ~260 au.

We must stress that our results are based on small number statistics. However, the same trends are found for asteroids and comets, and the apparent gaps in the distribution of aphelia are very unlikely to be the result of Neptune’s perturbations or observational bias. Perturbations from trans-Plutonian objects of moderate planetary size may be detectable by the New Horizons spacecraft (Iorio 2013).

[scalbers]

In terms of visual magnitude, if an Earth size planet with the same albedo were located at 250AU it should be about 20th magnitude. Just takes a good search, and is even within "amateur" search range.

[Vultur]

Are these objects supposed to be too cold for WISE to have seen? IIRC WISE was supposed to have ruled out Saturn+ planets out to some huge distance...

[Mongo]

Kevin Luhman reported that WISE found that no undiscovered object the size of Saturn exists out to a distance of 10,000 AU, and no object larger than Jupiter exists out to 26,000 AU. Objects at 200 or 250 AU would need to be much smaller to remain undetected to date, maybe no more than two or three times the mass of Earth. The linked paper suggests a mass "larger than the Earth".

[Hungry4info]

Some clues to the composition of the rings of Chariklo.

Photometric and spectroscopic evidence for a dense ring system around Centaur Chariklo
http://arxiv.org/abs/1407.4599

The rings have water ice, the surface of Chariklo does not. Both have amorphous carbon, amorphous silicates and organics.

[Hungry4info]

And now evidence of a ring system around Chiron.

Possible ring material around centaur (2060) Chiron
http://arxiv.org/abs/1501.05911

We propose that several short duration events observed in past stellar occultations by Chiron were produced by rings material. From a reanalysis of the stellar occultation data in the literature we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates l=(352+/-10) deg, b=(37+/-10) deg or l=(144+/-10) deg, b=(24+/-10) deg . The mean radius of the rings is (324 +/- 10) km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both imply lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23-m CAHA telescope and indeed its amplitude is smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at CASLEO 2.15-m telescope that is consistent with our predictions. Out of the two poles the l=(144+/-10) deg, b=(24+/-10) deg solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole, Chiron's long term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings as the tilt angle with respect to the Earth changes with time. Also, the variability of the water ice band in Chiron's spectra in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on the reasons why rings might be common in centaurs. We speculate on whether the known bimodal color distribution of centaurs could be due to presence of rings and lack of them.

[TheAnt]

That's a tiny ring system compared to this one! =)

[Paolo]

I finally had time to read the paper today and I was wondering: could rings around Centaurs be the natural outcome for orbiting chunks like those detected by Rosetta around C-G?

[TheAnt]

A new hypothesis for the origin of Sedna it is speculated that it has been stolen from a passing star, one that were slightly more massive than the Sun.
Grand theft Sedna

[ZLD]

If that is true, I believe Sedna should move to one of the highest priorities for mission design. Its going to be a while before we have a good slingshot trajectory with any planets really. Maybe make this a multi-flyby mission with different instruments, maybe somehow come up with a way to drop a lander that would survive a high velocity impact. And of course, lots of RTGs all around for longevity and after-mission potential as well. This is the best chance possible to "visit" another star system up close.

[SFJCody]

I think we should wait for the results from next generation surveys with telescopes like LSST or Pan-STARRS. There may be things out there that are even stranger and more worthy of a spacecraft visit. But if that turns out not to be the case, I agree that Sedna should be a priority for an ice-giant->TNO->interstellar-boundary spacecraft.

[ngunn]

A new hypothesis for the origin of Sedna

It's always been one of the hypotheses and, I agree, a very good reason to go there.

[Paolo]

in his book "50 years on the space frontier" spaceflight mechanics guru Robert Farquhar gives some detail of a New Horizons-like mission to Sedna, launching in April 2033, flying by Jupiter in June 2034 and by Sedna in September 2051, 78 AU from the Sun.
a similar mission to Eris would launch in 2032 and reach Eris only a few months earlier, in April 2051, 93 AU from the Sun