Earth-Sized World Could Lurk in Outer Solar System

[cyclonebuster]

That's correct, it would take a significant amount of time. Obviously, the reason detecting exoplanets via occultation is do-able is that we have a visible and bright target - the exoplanet's primary. In the case of a Rogue Planet, with low albedo and no primary that it's orbiting in a predictable fashion, it is impossible to pick out of the dark. An occultation would be a chance encounter. Or, historical images over time could be re-analyzed to see if any such occultations occurred, but weren't noticed at the time.

With respect to the historical record, the various mass extinctions in the past (which may or may not have necessarily been due to an impact event) don't match up to any predictable and regular interval, which might be indirect evidence of a periodic body passing near. Regrettably, it isn't there, and so makes the case for "Planet X" weaker.

Here's the url for an extinction graph: http://users.tpg.com.au/users/tps-seti/crater_age_6.gif - it's too large for the post frame.

I don't know about a weaker case for "Planet X". If you look at the Paleomap here it seems every 145 million years or so we get this cooling period or glacial age????? Is it because of impacts and or something pasing by? Perhaps, a dwarf star or another sun?

 

[yevaud]

That's a known quantity, e.g. the episodic variability of our parent star, which can vary it's output by a percent or so occasionally, over longish periods of time.

This covers it fairly well: http://en.wikipedia.org/wiki/Solar_variation

 

[h2ouniverse]

They're not designed to resolve objects at such a close distance.

WISE is infra-red, for quite short wavelengths (NIR/MIR) => able to detect gas giants that emit a lot of "hot" infra red radiation. But an Earth-sized object there would likely have its external layer (surface or outer atmosphere) ultra cold so would emit in the far infra red (FIR), therfore escaping detection by WISE.

Maybe if this is a "pontic planet" (with a free ocean, heated by radiogeny, kind of mini-Neptune) the IR flux would be detectable by WISE but this is not what the WISE team expects apparently.

 

[MeteorWayne]

The term "ablation" is pretty specific. To be ablated requires something to do the ablating, does it not?

For example, this was imaged during Shoemaker-Levy, "Just before reaching Jupiter, the Hubble Space Telescope took this view of some of the comet's fragments, enlarged enough to show cometary material ablating off in a direction away from the solar wind: " http://rst.gsfc.nasa.gov/Sect19/Sect19_23.html

The following backs this up, "The other class consists of comets which are relatively small "dirty ice balls" or a nucleus of ice and rock. As those with certain orbits approach the Sun, the solar wind and other forces cause them to ablate..." http://www.fas.org/irp/imint/docs/rst/S ... 19_22.html

The definition I find is "Ablation means removal of material from the surface of an object by vaporization, chipping, or other erosive processes." which leaves all doors open as to specific methodology

 

[yevaud]

Oh, I don't disagree, though the term ablation is, technically, usually utilized to describe an outside influence ablating material off a body, as in, "the laser ablated a thin layer of material from..." Still and all. Not important.

Interesting thread, is it not?

 

[MeteorWayne]

Oh, I don't disagree, though the term ablation is, technically, usually utilized to describe an outside influence ablating material off a body, as in, "the laser ablated a thin layer of material from..." Still and all. Not important.

Interesting thread, is it not?

Yes it is an interesting thread! I should point out that using a laser to ablate material is closer to EM radiation from the sun than the particulate nature of the solar wind

 

[yevaud]

Point noted.

 

[Astro_Robert]

As far as glacial ages or mass extinctions being evidence for Planet X or some other solar companion. Some folks proposed a red dwarf star they called 'Nemesis' many years ago, and while it was interesting I don't believe has much following. Just think, how many 65-140MY orbits about our sun are there?

Other people have proposed that extinctions could be due to our solar system crossing the plane of the galactic disk and facing increased influence due to other celestrial objects. There are many theories, but some people also believe that rare nearby supernovas or other phenomenon could have accounted for one or two extinctions, lessening the need for a regular periodic climate disruptor from a large companion or other solar system interaction.

 

[Astro_Robert]

For those interested, I found that wikki actually has a fairly good writeup on the subject of planet X.
http://en.wikipedia.org/wiki/Planets_beyond_Neptune

Near the bottom there is adiscussion about subsequent theories for Planet X, among them the Kuiper cliff. Here it is mentioned that an Earth mass object could exist and account for observations of the Kuiper Belt if it was far enough out, and in a highly eliptical orbit. That is not to say that it does exist, or that we would know where to look for it based on what we know now, but that given what we know it would be plausible.

One of the article I read through the other day also explored this and indicated that as we discover more Trans-Neptumion Objects (TNOs) we could notice if there are any orbital periods that have been depleted, which do not correspond to a resonance with Neptune. Any such findings could point to a Planet X.

Betwwen WISE, PanSTARRS and LSST, hopefully we will find at least some answers in the next several years.

 

[Couerl]

I wonder where the number 900 comes from? If he is talking about Pluto sized bodies I might buy a small fraction of that number, but it seems to me anything that far away from the suns gravity wouldn't stand much chance, nevermind enough time in such a volume for the accretion of enough material to become so large. Even if one speculates that the original cloud of gasses and debris that formed the solar system to begin with had a lot more "chocolate chips" in the recipe than had been originally surmized, one would expect there to be far more planetary bodies closer to the sun to begin with. I think 900 is pushing it..

Nonetheless, even a fraction of that number could be big in the long run and another earth sized body, even if it were nothing more than a ball of rock and ice could be particularly useful if for no other reason than having a similar gravity to our own planet. I suppose I'll buy that when I see it.

 

[Ogeon]

I wonder where the number 900 comes from? If he is talking about Pluto sized bodies I might buy a small fraction of that number, but it seems to me anything that far away from the suns gravity wouldn't stand much chance, nevermind enough time in such a volume for the accretion of enough material to become so large. Even if one speculates that the original cloud of gasses and debris that formed the solar system to begin with had a lot more "chocolate chips" in the recipe than had been originally surmized, one would expect there to be far more planetary bodies closer to the sun to begin with. I think 900 is pushing it..

While I agree that 900 may well be as far out as the theoretical planets that we are discussing, the possibility of some rather large planets could very well be possible. A larger planet could have formed much closer and then been thrown out into the outer reaches of our solar system by some force, such as a collision with another planet. The theory that our own planet may have been hit by another early in its life is gaining popularity. For all we know, the asteroid belt could have been a larger planet(s) that didn't survive a collision with another planet. One of those possible planets could have been kicked out of the neighborhood and survived more or less intact. No doubt much stranger things have happend

 

[Astro_Robert]

I believe bodies being ejected or otherwise changing orbits are usually moved about through gravitational perturbations rather than through stochastic processes or impacts. Think about the moon; it is widely held that it was created when a Mars-sized (~1/10th Earth mass) protoplanet colided with Earth 4+B years ago, yet the Earth was not ejected into the cold outer reaches. Also note that astronomers believe that Uranus lies on its side due to a probably impact, yet it was not ejected either.

Whereas, we have sent many spacecraft to the outer solar system by getting a gravitational boost from Jupiter. The famos three-body probem in astronomy also usually results in ejection. Collision just results in one or more bodies being disrupted or absorbed.

On the other hand, many astronomers now support the idea of planetary migration, whereby the gas giant (and possibly terrestrial) planets formed closer in and then pushed eachother outwards until the perturbations grew small enough that they settled in their current positions. In fact, some people believe that Uranus switched places with Neptune during this time.

As far as 900, that is a statistical estimate based on what fraction of the sky we are able to reliable scan with our current technology verses the number of detected object of a given size. Pluto sounds large, and 900 sounds large, but really at ~1,000 miles in diameter something like 500 could physically fit within the Earth volumentrically. Mass wise, even 900 may even be less massive than 1 Earth mass. Also note that Astronomers base their size-quantity estimates off of their experience with the main asteroid belt where size is fairly well known and sample saize is large. When one gets down into lower quantities random effects can throw it off, i mean you might have 2 Earth sized objects, or you might have none, and both scenarios would be statistically valid.

 

[h2ouniverse]

I wonder where the number 900 comes from? If he is talking about Pluto sized bodies I might buy a small fraction of that number, but it seems to me anything that far away from the suns gravity wouldn't stand much chance, nevermind enough time in such a volume for the accretion of enough material to become so large. Even if one speculates that the original cloud of gasses and debris that formed the solar system to begin with had a lot more "chocolate chips" in the recipe than had been originally surmized, one would expect there to be far more planetary bodies closer to the sun to begin with. I think 900 is pushing it..

Nonetheless, even a fraction of that number could be big in the long run and another earth sized body, even if it were nothing more than a ball of rock and ice could be particularly useful if for no other reason than having a similar gravity to our own planet. I suppose I'll buy that when I see it.

According to current dynamic evolution models, the vast majority of the planetesimals originally in the Kuiper Belt (the primordial one is believed to have lied between closer to the sun that today) have been ejected from the belt either towards the Sun (then destroyed) or outwards. Many of the ones ejected outwards should have left the system. But this is not unlikely that thousands of them above 500km in diameter would still orbit the Sun. As far as bigger objects are concerned, the current thinking is that the Solar System stability is marginal: i.e. planets form largely in excess of what the system can cope with dynamically and are ejected gradually until the number and position corresponds to a relative stability. Even then major events (ejections or collisions) can still occur in the long run. It seems logical to me that such mid-sized planets would have the same fate as the planetesimals: destruction in the Sun, destruction by collision, ejection from the system or scattering into the fringes. This is this latest category that matters then.
So imnsho this is not a question of presence of material in the protostellar disk at 1000 AU but of formation close to the Sun followed by scattering.

Then the orbits would not be circular but extremely elliptical. One should remember that an object on a Sedna-like orbit spends less than 2% of its time at less than 100AU (hence in the current observable zone). This is what leads M.E. Brown to assess that the most probable number of Sedna-like objects on Sedna-like orbits is about 40.
For an orbit with an aphelion at 10000AU and a perihelion beneath 100AU, this relative duration is even shorter. If there were ten planets on such 100-10000AU elongated orbits the probability that one of them would be currently at less than, say, 200 AU, would be very small.

 

[MeteorWayne]

Great post, H20universe!

 

[Couerl]

Hi and thank you for the responces.

 

[BxDee]

was wondering, every means of detection that has been mentioned here is passive detection (ea. direct or relflected light or the blocking of light in what ever wave length).

what about active detection? i mean satelites that are being sent to the outskirts of our solar system like the voagers and new horizons could be fitted with some sort of system like the echo localization we use on fish or like radar used to find boats/planes etc (same principle in both i know) , now u would ofc need a network of thise that where connected together somehow and also ofc timeconsuming thinking of the distnaces involved, but surly possible...

also, would there be a possiblilty of detecting gravity destortions/pull from other big plante sized objects that far out?
i guess this would be categorized as "passive detection" but sending a fleet of satelites out to the rim like that would count as "active" in my book.

that far out the gravity pull from the sun is prob very little, but prob detectable with instruments, same with the gas giants (when they orbit "close" enough to any given detection satelite). but that far out im guessing u will not be able to detect gravitational pulls from the known rocky planets of our solar system.

but this is just me spit balling... but im willing to bet that New horizons have instruments to detect gravitaonal effects, they might not be as sensitive as needed for what im sugesting tho. and im sure the voagers dont have that sorta instruments (i might be wrong), but the voagers are still collecting important data and sending home so who knows what they have of detectors onboard.

im sure that if they (voagers and NH) have gravity detectors onboard, they could prob be able to detect a object as massive as a brown dwarf (nemisis).
(loved the nemisis refference in the series Eureka a while back, come to think of it i think they used gravitational messurements of the solar system from a prob to find it, and determin it would come into play in 3000 years).

but surly gravitational and echo/radar detection from satelites would work given the right amount of time and money?

 

[MeteorWayne]

Actually, every spacecraft and every asteroid that we track "out there" is a gravity probe. Any massive object will affect te motion of every other object. Yes it's passive, but it would detect a large object. There is no "gravity detecting" instrumentation you could add to a spacecraft. As far as echo location, or radar, the objects are way too far apart for that to be effective. Of course, if we sent a fleet of thousands of probes with such capability, we might detect more TNOs, but there's certainly no money for such a mission, andthe time would be substantial. Good tracking of what we discover already will answer any questions about massive objects eventually.

 

[OmicronPersei8]

Back in the 90s there was a paper called "Possibility of Life Sustaining Planets in Interstellar Space" , which argues that there could be Earth-sized bodies out there with thick hydrogen atmospheres, which thanks to a greenhouse-effect + geothermal heat could have life-sustaining temperatures at the surface. I'll just quote the wikipedia summary in their "Rogue Planets" article:

"In 1998, David J. Stevenson authored a paper entitled "Possibility of Life Sustaining Planets in Interstellar Space."[6] In this paper, Stevenson theorizes that some planet sized objects, referred to as "planets", drift in the vast expanses of cold interstellar space and could possibly sustain a thick atmosphere which would not freeze out due to radiative heat loss. He proposes that atmospheres are preserved by the pressure-induced far infrared radiation opacity of a thick hydrogen-containing atmosphere.

It is thought that during planetary system formation, several small protoplanetary bodies may be ejected from the forming system.[7] With the reduced ultraviolet light associated with its increasing distance from the parent star, the planet's predominantly hydrogen and helium containing atmosphere would be easily confined even by an Earth-sized body's gravity.

It is calculated that for an Earth-sized object at a kilobar hydrogen atmospheric pressures in which a convective gas adiabat has formed, geothermal energy from residual core radioisotope decay will be sufficient to heat the surface to temperatures above the melting point of water.[6] Thus, it is proposed that interstellar planetary bodies with extensive liquid water oceans may exist. It is further suggested that these planets are likely to remain geologically active for long periods, providing a geodynamo-created protective magnetosphere and possible sea floor volcanism which could provide an energy source for life.[6] The author admits these bodies will be difficult to detect due to the intrinsically weak thermal microwave radiation emissions emanating from the lower reaches of the atmosphere.

A study of simulated planet ejection scenarios has suggested that around five percent of Earth-sized planets with Moon-sized moons would retain their moons after ejection. A large moon would be a source of significant geological tidal heating.[8]"


The article has a link to a free pdf of the original paper. There's also this article:
http://www.nytimes.com/1999/07/06/healt ... wanted=all

Anyway, I'm supposing that this could also concievably apply to an Earth-sized object in the far outer solar system. I don't really know enough to evaluate all this myself but it sounds kinda neat!

I suppose it all might depend on how the object formed and what happened to it before arricing at its present location. If it didn't collect enough gases it would just freeze over I suppose. If it formed like a giant Pluto except surrounded by that thick gas enveloupe I suppose it would be a giant slushball (provided the radioactive decay provided enough heat). Without all those gases you could still have underground liquid water due to geothermal activity;.