Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Astrofan on 30/06/2007 06:56:07
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Dr Steinn Sigurðsson (Penn State) has been reporting findings announced at the Confererence on Extreme Solar Systems on his blog Speculation of another Neptune in the Solar System at the Conference of Extreme Solar Systems, Santorini (http://scienceblogs.com/catdynamics/2007/06/extreme_solar_systems_v_the_sa.php)but amongst all the interesting discoveries is this idea raised by planetary dynamicist Dr Ed Thommes:
"Looks like the outer solar system, with late heavy bombardment, would have come together nicely if there was another Neptune out there to begin with."
"So we let debris drag bring Jupiter and Saturn into resonance with a little bit of orbital migration, scatter Uranus and Neptune out (and use the debris to recircularise) and we get the details more or less right if we let a second Neptune have been there and been ejected, either to infinity or outer Oort cloud."
Now this could really be quite fascinating. I recall reading that the mass of all TNOs, SDOs, and LPCs added up together cannot be more than a few Mearths at best. A far cry from the predicted 10-30 Mearths postulated to have existed in those nether regions i.e. the Edgeworth-Kuiper Belt (EKB), Scattered Disk (SD) in the beginning.
Also Levison et. al., (see *1) have studies which imply that the original mass in planetesimals between 4 and 40 AU was about 4 times the mass in solids in a minimum-mass solar nebula. While this mass is reasonable, he and his team is of the view that the standard model makes predictions that are not borne out by observation. Specifically, this is what he said "(1) the inferred population of the scattered disk is much smaller than predicted ([3],[4]); (2) OC comets appear to form at colder temperatures than our results would suggest ([5]), and (3) models for the origin of Halley-type comets (HTCs) require a massive inner OC or scattered disk as a source region for the HTCs." The unusual path that supercomet 2000 CR105 takes is also suggestive of a perturbative presence somewhere deep within the Scattered Disk IF not beyond, Levison:
"Undoubtedly, something massive knocked the hell out of the belt, the question is whether it's there now."[
So what really did happened to the missing mass (i.e. of these TNOs, SDOs, LPCs, etc) in the EKB, SD and inner Oort cloud? And why do the solar system's outliers like dwarf planet Eris (ex Planet X), Sedna ala 2003 VB12 and CR 105 have such high orbital inclinations (i) of 44.187°, 11.934° and 22.770° (see *2, *3 & *4) respectively? Or why are their orbits so eccentric (e.g. e=0.44177, e=0.855, e=0.798)? Also why the abrupt sharp edge to the Classical EKB at 50 AU (see *5) ? What could have produced it? Could there have been numerous factors at play with regards to these anomalies? Or could any or all of these anomalies be the by-products of a stellar flyby, flybys by BDs or planetary mass (i.e. planemos) interlopers maybe even a Planet X? And why not but the net result of perturbation by a distant substellar mass BD common proper motion solar companion (especially at periastron)?
I have come across a paper by Morbadelli et al., where it was argued that a ~50 MJup rogue BD flyby can account for the perturbed orbits of some of these outer solar system bodies and they even suspect that Sedna could actually be but an extrasolar planetoid captured from this rogue BD. It begets the question i.e. let's assume that they are right, that indeed this BD interloper is the culprit responsible, but what if it wasn't simply just an interloper? What if it was of a lower mass and really but a highly eccentric (0.9 <= eBD <= 0.99), 13 MJup <= Mbd <=20 MJup coeval substellar mass BD companion to our Sun or maybe even a captured ultracool VLM substellar companion (given the likely birth of the Sun in an Orion like open cluster and the case of B1620-26c (see *6), this can't be entirely ruled out or can it?) with a periastron at 100-200 AU instead?
The Teff of such an object is likely to be only about ~369.14 ° K (let's assume that it is of the same age as the sun i.e. 4.6 Gyrs and has a mass of 15 MJup for the sake of discussion) according to Burrows et al., and if it still around, could be near or at apastron at this moment i.e. almost a light year away. Detecting it sure won't be an easy task, for if we are still turning up more M Dwarfs in what is the solar neighborhood's own backyard as evidenced from the RECONS project (see *7) and elsewhere even at this day and age, one can imagine how very much more tedious is the task of locating objects such as BDs with even lower masses, Teffs, and SpTs e.g. T or Y.
Gomes et al., likewise have also come to a rather similar conclusion like Levison et. al., albeit one involving even lower masses perturbers and maybe with particular interest and relevance here is that one of the possibilities involves having a Neptune mass planet out at semiminor axis 2000 AU or a Jovian with semiminor axis at 5000 AU.
References:
Morbidelli, A., & Levison, H. F., 2004, Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna), AJ, 128, pp. 2564-2576
Burrows, A., Marley, M., Hubbard, W. B., Lunine, J. I., Guillot, T., Saumon, D., Freedman, R.; Sudarsky, D., & Sharp, C., 1997, A Nongray Theory of Extrasolar Giant Planets and Brown Dwarfs, ApJ 491, p.856
Gomes, R. S., Matese, J. J., & Lissauer, J. J., 2006, A distant planetary-mass solar companion may have produced distant detached objects, Icarus, 184, pp. 589-601
Links:
*1
Mass Deficit in the Outer Solar System (http://www.aas.org/publications/baas/v32n3/dps2000/498.htm)
*2
Eris (http://en.wikipedia.org/wiki/Eris_(dwarf_planet))
*3
Sedna (http://en.wikipedia.org/wiki/90377_Sedna)
*4
CR 105 (http://en.wikipedia.org/wiki/2000_CR105)
*5
The Calssical EKB (http://www.ifa.hawaii.edu/faculty/jewitt/kb/kb-classical.htm)
*6
Captured Pulsar Planet (http://en.wikipedia.org/wiki/PSR_B1620-26c)
*7
RECONS (http://www.noao.edu/outreach/press/pr06/pr0614.html)
*8
The Challenge of Detection Limit
Let us for the sake of convenience, affix a mass of 15 MJup for this hypothetical BD comapnion. And let us also assume that it is an coeval companion to our Sun i.e. age = 4.6 Gyrs. According to Burrows et. al (1997), such a BD has a Teff of 369.14 °K and a luminosity of 7.19179 * 10^-7 Solar.
Effective temperature (Teff) of the Sun = 5778 °K
Effective temperature (Teff) of this hypothetical BD companion 369.14 °K
Flux 1/Flux 2 = constant * (5778)^4/constant * (369.14)^4
= 1.114577188 * 10^15/1.85679707025 * 10^10
i.e. The SUN is 60026.87278 times BRIGHTER than the hypothetical BD companion
At T = 369.14 ° K
Lamda (Max) = 0.2897/369.14
Lamda (Max) = 0.000784797096 cm K
Now let us also assume the location of our hypothetical BD companion to be 50000 AU. Light has to travel out to 50000 AU, get reflected and come back 50000 AU. This is where the assumption that the planet is in opposition comes in. If the BD is in opposition, then the Earth is in between the Sun and the BD and as the distance between Earth and Sun is 1 AU, the distance between Earth and the BD is 49999AU. Similarly, during opposition, the distance between Earth and Jupiter is 4.2 AU.
Now, by the time the energy of the Sun travels to 50000 AU, the flux is down in comparison to the flux at Jupiter by (50000/5.2)^2. In addition, the reflected light has to travel back 49999 AU from the BD in comparison to only 4.2 AU from Jupiter. Hence, the flux of the reflected sunlight from the planet is below that of Jupiter by a factor of (50000/4.2)^2. Hence, the visual light flux from the planet is below that of Jupiter by a factor (50000/5.2)^2 * (49999/4.2)^2. We know the magnitude of Jupiter (i.e. -2.7 at 5.2 AU). Hence, apply the formula for magnitudes and we'll get the magnitude of the BD companion.
At 50000 AU,
(50000/5.2)^2 * (49999/4.2)^2 = 1.310259681 * 10^16
m1 - m2 = 2.5*log(F2/F1)
m1-(-2.7) = 2.5*(16.11735738)
m1-(-2.7) = 40.29339344
m1 + 2.7 = 40.29339344
m1 = 37.79339344
Apparent Visual Magnitude of this Hypothetical BD companion will be but a DIM 37.79339344 i.e. definitely way beyond the Hubble Space Telescope's (HST) power.
Levison et al's BD Interloper Paper (http://adsabs.harvard.edu/abs/2004AJ....128.2564M)
Burrow et al's Non Gray Theory of EGPs & BDs (http://adsabs.harvard.edu/abs/1997ApJ...491..856B)
Gomes et al's Low Mass Planetary Companion Rogues (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4KGX8CX-1&_user=10&_coverDate=10%2F31%2F2006&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=166ab83466a4791068714c059b13149d)
Terminology:
TNO = Trans Neptunian Objects
SDO = Scattered Disk Objects
LPCs = Long Period Comets
Mearth = Number of Earth Masses
OC=Oort Cloud
Edgeworth-Kuiper Belt=EKB
SD=Scattered Disk
HTC=Halley-Type Comets
i=Orbital Inclination
e=Orbital Eccentricity
BD= Brown Dwarf
MJup=Jupiter Masses
Mbd=Mass of the BD
eBD=Eccentricity of the BD
Teff=Effective Temperature
VLM=Very Low Mass
Substellar=Of a subsolar value i.e. lower than Sun's value
Gyr=Billion of years
AU = A unit of measure in the cosmos. 1 Astronomical Unit (AU)=the distance of the Earth to the Sun i.e. 146, 900, 000 Km
SpT=Spectral Type
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This wordy document appears to suggest that there might be an undetected brown dwarf companion to the sun in the outer solar system. This may not have been detectable by optical telescopes but infra red telescopes would easily detect such an object and several infra red teleshopes have done full sky surveys so I consider that it is unlkely that it is there or if it is it is not of any siginficant size because gravitational anomalies over hundreds of years of observation would have shown it up
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This theory has been around for quite a while but, as Ian said, thus far there is no evidence whatsoever for its existence.
Taken from http://en.wikipedia.org/wiki/Oort_cloud (http://en.wikipedia.org/wiki/Oort_cloud)
...physicist Richard A. Muller and others have postulated that the Sun has a heretofore undetected companion (brown dwarf or gaseous giant planet) in an elliptical orbit beyond the Oort cloud. This object, known as Nemesis, is theorized to pass through a portion of the Oort cloud approximately every 26 million years, bombarding the inner solar system with comets. Although the theory has many proponents, no direct proof of the existence of Nemesis has been found.[18] Furthermore, many argue that a companion star at such a great distance could not have a stable orbit, as it would probably be ejected by perturbations from other stars.
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Soulsurfer, perhaps you may want to read on. A VLM companion (be it a Jovian planet or a full fledged deuterium fusion capable (i.e. 0.012-0.075 Msun (assuming Fe/H = 0.0 i.e. Solar Metallicity), personally I think such a BD comapnion (it should not be more massive than 0.02 Msun though) exist, it could well be picked up by JWST/WISE but maybe not Spitzer, given the latter's smaller field of view. Or it could also be that someone notices an object with an unusually high parallax. The recent discovery of SO025300.5+165258's i.e. a SpT M6.5 Dwarf by Teegarden et al., (2003), proves that relative brightness is NO 100% guarantee of certain detection.
For all we know, such a companion could well be sitting as yet unnoticed and buried amongst the countless millions upon millions of objects in the databases (e.g. 2MASS, SDSS, DENIS, SuperCOSMOS, NEAT, LINEAR, etc) aka LP944-20 (i.e. this BD should INSTEAD of Gl229b be actually the first BD discoverd. It was first sighted by Luyten and Kowal in 1975 BUT not seen again till about 1997 (Tinney, 1998)) and HD 209458.
As for the gravitational anomalies you are saying, they have i.e. the perturbed orbits of Eris, Sedna and CR 105, the abrupt termination of the Classical EKB at ~50 AU, and the problem with the mass shortfall in the EKB, SD and OC.
References:
Teegarden, B. J., Pravdo, S. H., Hicks, M., Shaklan, S. B., Covey, K., Fraser, O., Hawley, S.L., McGlynn, T., & Reid, I. N., 2003, "Discovery of a New Nearby Star", ApJ 589, pp. L51-L53
Tinney, C. G., 1998, "The intermediate-age brown dwarf LP944-20", MNRAS 296, L42-L44
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I guess some if not all of you have heard of Dr J. D. Kirkpatrick. He is perhaps the world's top BD hunter par excellence. I hope he doesn't mind that I share with you on what he has shared with me and thinks about ultracool VLM BDs and prospects for a distant substellar companion for our Sun along with some other arguments for it from various sources.
In Burrows et al, 2003, the paper states that SIRTF (ala Spitzer)/MIPS should be able to detect at 10 parsecs (i.e. 1 parsec or 1 pc = 206265 A.U. = 3.26162 Light Years) the ~24 µm flux of objects more massive than 2-4 MJ at age 1 Gyr or more massive than 10 MJ at 5 Gyr. In the opinion of the authors, the most relevant channel on MIPS for brown dwarf studies is ~1000 times better in imaging mode than for the pioneering IRAS. While Spitzer is the last of the "Great Observatories," and will view the sky with unprecedented infrared sensitivity, JWST will in turn provide a two- to four-order-of-magnitude gain in sensitivity through much of the mid-infrared up to 27 microns. However the JWST/NIRCam is greater than one hundred times more sensitive than HST/NICMOS at 2.2 µm and enables one to probe deeply in space, as well as broadly in wavelength. In its broadband detection (imaging) mode, JWST/MIRI will be ~100 times more capable than SIRTF from ~5 µm to ~27 µm. Since the mid-IR is one of the spectral regions of choice for the study of the coolest brown dwarfs, MIRI will assume for their characterization a role of dramatic importance.
Kirkpatrick in private, seems especially excited about WISE as he revealed this to me: "The one mission best suited to find ultracool VLM BDs (like the proposed BD companion) is WISE, the Wide Field Infrared Explorer formerly known to all as NGSS. In fact, finding the nearest BD (expected to be closer than Proxima) is one of its two main science goals." He is however, at best, skeptical as to how successful instruments/surveys like Keck Interferometer, SOFIA, SIRTF (ala Spitzer), IRIS and Herschel Space Observatory will be in finding Free Floating Planetary Mass Objects and ultracool BDs (e.g. the proposed BD companion). The Keck Interferometer he asserts doesn't work at those wavelengths (wavelengths that approximates the expected Teffs of these low mass objects e.g. N-band). Herschel works at much longer wavelengths. The others (e.g. SIRTF, SOFIA and IRIS) are in the ballpark, but both SOFIA and SIRTF have very small fields of view. So to find a very low-mass BD and Free Floating non fusors between here and Proxima would require them to get quite lucky. In other words, they'd have to be pointing in just the right spot.
In percentage terms, how many of the BDs found by the various surveys e.g. 2MASS, DENIS, Sloan Digital, NICMOS, SuperCOSMOS, etc have had their stellar types, proper motion and distances determined? How long will it all take for every object currently in the databases to have their stellar types, proper motion and distances measured? Will all the objects in the databases of the above 5 surveys have their nature and other characteristics ascertained before 2010?
Only about thirty or so BDs have had their parallaxes measured. A few more in addition have proper motion measures. It will likely never be the case in his lifetime (in Kirkpatrick's words) that all the known BDs will have their distances measured. Unless there is a dedicated space mission that goes much deeper than Hipparcos and is dedicated to specific targets like BDs, Kirkpatrick does not think this will ever be done completely.
Kirkpatrick shared with me that there are only but a few astronomers around even pursuing parallax measurements, and many of them are meeting resistance because parallax work isn't "sexy". It's of fundamental importance to understanding these objects, though, but not everyone agrees that it's important enough to spare the time and resources on.
In our numerous correspondence, I asked Kirkpatrick this: Given that the Universe is ~14 Gyrs old, what is the likelihood that old i.e. >10 Gyrs VLM stars with Masses in between 75 to 80 Mj may lurk as yet undiscovered or their nature as yet unresolved within 1-10 Light Years (L.Y.) of the Sun? This is what he said there are still a few of those out there, but it's solely because our searches are incomplete and not because these objects are harder to find than BDs. They're actually a lot easier to find because they're hydrogen burners and emit more light than the BDs.
Dr. J.D. Kirkpatrick in private email correspondence and also Kirkpatrick (2003) has related i.e. that the population census of Very Low mass objects like Late Type dwarfs e.g. M and stellar L dwarfs (i.e. SpT <L5) and especially that of BDs is as yet incomplete perhaps by as much as 50%.
While undoubtedly, the technology available is getting better and better with each passing day, scarce resources e.g. manpower and money; human prejudices and carelessness (i.e. in overlooking potential discoveries) can all render the BEST intentioned efforts useless.
An outline on the NGSS/WISE mission (Kirkpatrick, 2003) in which it was stated that the census of Low mass and cool BDs in the space between the Solar System and Proxima Centauri with Teff down to about 150°K is probably incomplete. i.e. quote from article: "there should be at least ~200 brown dwarfs with M > 10 MJup within 8 pc of the Sun."
If there are 200 BDs within 8 pc, then each BD occupies its own [(4/3) * pi * (8pc)^3]/200 = 10.7 pc^3. Out to Proxima Centauri there is a volume of space equal to [(4/3) * pi * (1.3pc)^3] = 9.2 pc^3. So, if we get lucky, there might be one BD closer than Proxima since the sphere of space centered on the Sun ought to have one such object in a volume slightly larger than that out to Proxima. So, if there are actually more than 200 BDs within 8pc (and what Kirkpatrick quoted here was just a lower limit to the expected numbers i.e. there are probably >200 BDs within 8 pc), then the likelihood of a BD closer than Proxima goes up.
Thus, it's still within the realm of possibility that the Sun could indeed have a very cold BD companion that we haven't discovered yet. Kirkpatrick also disclosed that it's things like that that keeps him going sometimes, too!
References:
Burrows, A., Sudarsky, D., Lunine, J. I., 2003, Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs, ApJ, 596, pp. 587-596
Kirkpatrick, J. D., 2003, The Next Generation Sky Survey and the Quest for Cooler Brown Dwarfs, IAU Symposium Vol. 211 ("Brown Dwarfs")
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This theory has been around for quite a while but, as Ian said, thus far there is no evidence whatsoever for its existence.
Taken from http://en.wikipedia.org/wiki/Oort_cloud (http://en.wikipedia.org/wiki/Oort_cloud)
...physicist Richard A. Muller and others have postulated that the Sun has a heretofore undetected companion (brown dwarf or gaseous giant planet) in an elliptical orbit beyond the Oort cloud. This object, known as Nemesis, is theorized to pass through a portion of the Oort cloud approximately every 26 million years, bombarding the inner solar system with comets. Although the theory has many proponents, no direct proof of the existence of Nemesis has been found.[18] Furthermore, many argue that a companion star at such a great distance could not have a stable orbit, as it would probably be ejected by perturbations from other stars.
Hiya DoctorBeaver, there are a few things here that distinguishes the object that I am proposing here has an orbit nowhere bear that of Hut's/Muller's Nemesis.
1.
It certainly does not goes out anywhere near halfway between Sol and Proxima.
2.
The original Nemesis was supposed to have been a M Dwarf. I know Muller and team later suggested that a BD is a distinct possibility too. But my object is definitely a BD.
3.
This BD companion I'm proposing is in no way responsible for any of the major mass extinction episodes in the Earth's history. It certainly has not the 26-32 million years orbital period of Nemesis.
4.
My arguments thus are not because of the mass extinction episodes that we need this BD but because of the missing mass in the EKB, SD, OC and the excited even disturbed orbits of objects like Eris, Sedna and CR 105 as well as the abrupt termination of the Classical EKB at ~50 AU.
5.
While I do not claim that I'm the 1st one to have proposed that our Sun has anything else that is more massive than the planets known to orbit it, as is evidenced by me quoting Morbadelli and Gomez amongst others, my reasons while some of them may overlap with those of Morbadelli/Levison or those of Gomez et al., others are unique e.g. the missing mass in the above mentioned regions and the sharp edge to the Classical EKB at ~50 AU.
Hope this clears things up.
Rgds
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I agree that isolated brown dwarf stars are very difficult to detect and can easily be missed and do not deny that what you say is possible. Planet hunters have turned up a few of them and that is where we are most likely to learn about their range and properties.
I also believe and have always believed that there is a good probability that there are quite a few objects like this around closeish to the sun to be detected
Please bear in mind that in these pages you are presenting to a general public and your writings are more suited for professional astronomy pages and in fact were probably copied verbatim from them. When faced with a heavy load of acronyms and mathematical detail most readers will turn off and ignore your input.
You seem to be quite knowledgable in the area so I will turn the question back towards you.
I am quite interested in the size versus numbers statistics of objects growing in condensing clouds expecting objects all the way from groups of molecules right up to 100 solar mass stars to appear in the statistics. The fact that the clouds eventually become mostly transparent implies upper limits to the density of very small particles but I see no reason why the numbers should not continue to increase as size deceases up to some quite small size limit.
In the past I have seen people arguing that it stops with small star or Brown dwarf sized objects but I was always suspicious of their arguments. Perhaps you can shed some light on this?
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Please bear in mind that in these pages you are presenting to a general public and your writings are more suited for professional astronomy pages and in fact were probably copied verbatim from them. When faced with a heavy load of acronyms and detail most readers will turn off and ignore your input.
Concepts, facts and figures are indeed lifted off professional literature in the public realm. They have to be I can't invent them if I want to be at all credible right? ;) But the theory itself is wholly my own work. Something that I've worked on on off for the last 5 years or so. I do get what you mean with regards to the verbosity and complexity of the issues that are discussed in this thread. I have already factored that into consideration. Just that I thought some of you who have the knowledge may be willing to help me out a bit with it i.e. by pointing out any misconception, correcting any mistakes including terminology and grammar employed, etc.
You seem to be quite knowledgable in the area so I will turn the question back towards you.
I am quite interested in the size versus numbers statistics of objects growing in condensing clouds expecting objects all the way from groups of molecules right up to 100 solar mass stars to appear in the statistics. The fact that the clouds eventually become mostly transparent implies upper limits to the density of very small particles but I see no reason why the numbers should not continue to increase as size deceases up to some quite small size limit.
In the past I have seen people arguing that it stops with small star or Brown dwarf sized objects but I was always suspicious of their arguments. Perhaps you can shed some light on this?
Soulsurfer, I'm not someone who is into molecular clouds or star formation. I'm more of a person who is into Theoretical Modelling of the atmospheres and Interiors of BDs and EGPs and the Minor Planets/TNOs with perhaps some passing interest in orbital dynamics as well.
You need someone who is to afford you the answers you seek. Try searching on things like IMF (i.e. Initial Mass Function), molecular clouds, starless cores, etc on Arxiv (http://arxiv.org/find/astro-ph) and the NASA Astrophysics Data System (http://adsabs.harvard.edu/preprint_service.html) perhaps. You should be able to come up with a number of names i.e. mostly Profs and Drs in Astrophysics/Cosmology with email contacts (if not google for their email addresses by doing a search on their names).
While not all may respond to your queries, some will. That's how I got to learn what I've learnt about Celestial Mechanics, the EKB, SD, OC and minor planets, BDs and EGPs, etc by keeping the likes of Profs. Tremaine, Lunine, Basri, Scarfe, etc; Drs Kirkpatrick, Wiegert, Holman, Sigurðsson, etc busy ;). Sorry that I could not help you more Soulsurfer.
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Isn't there a space probe now on its way to Pluto? What happens to it once it is finished at Pluto, and what is it able to detect?
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The pluto express "new horizons mission" is on its way and has just sent picture back on its pass of Jupiter that sends it off out of the solar system. http://pluto.jhuapl.edu/ is hoped to detect other kuiper belt objects.
I had always been a bit suspicious about the gap that is shown between the Kuiper belt and the Oort cloud. I think that the detection of Sedna has something to say about it. The most probable thing is that there are a lot of things in elliptical orbits out there, they mostly spend their time in the outer limits known as the Oort cloud but most of them are in elliptical orbits and occasionally come much closer The reason for this is the effect of near passes of other stars.
If the objects in the Oort cloud had mostly circular orbits it is quite unlikely that disturbances to their orbits would send them close to the sun as comets, however if they were already in elliptical orbits with quite a high eccentricity. Small random changes would make it much more probable that they would head for the inner solar system.