‘Nomad’ Planets Could Outnumber Stars 100,000 to 1


Could the number of wandering planets in our galaxy – planets not orbiting a sun — be more than the amount of stars in the Milky Way? Free-floating planets have been predicted to exist for quite some time and just last year, in May 2011, several orphan worlds were finally detected. But now, the latest research concludes there could be 100,000 times more free-floating planets in the Milky Way than stars. Even though the author of the study, Louis Strigari from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), called the amount “an astronomical number,” he said the math is sound.

“Even though this is a large number, it is actually consistent with the amount of mass and heavy elements in our galaxy,” Strigari told Universe Today. “So even though it sounds like a big number, it puts into perspective that there could be a lot more planets and other ‘junk’ out in our galaxy than we know of at this stage.”

And by the way, these latest findings certainly do not lend any credence to the theory of a wandering planet named Nibiru.

Several studies have suggested that our galaxy could perhaps be swarming with billions of these wandering “nomad” planets, and the research that actually found a dozen or so of these objects in 2011 used microlensing to identify Jupiter-sized orphan worlds between 10,000 and 20,000 light-years away. That research concluded that based on the number of planets identified and the area studied, they estimated that there could literally be hundreds of billions of these lone planets roaming our galaxy….literally twice as many planets as there are stars.

But the new study from Kavli estimates that lost, homeless worlds may be up to 50,000 times more common than that.

Using mathematical extrapolations and relying on theoretical variables, Strigari and his team took into account the known gravitational pull of the Milky Way galaxy, the amount of matter available to make such objects and how that matter might be distributed into objects ranging from the size of Pluto to larger than Jupiter.

“What we did was we put together the observations of what the galaxy is made of, what kind of elements it has, as well as how much mass there could possibly be that has been deduced from the gravitational pull from the stars we observed,” Stigari said via phone. “There are a couple of general bounds we used: you can’t have more nomads in the galaxy than the matter we observe, as well as you probably can’t have more than the amount of so called heavy elements than we observe in the galaxy (anything greater that helium on the periodic table).”

But any study of this type is limited by the lack of understanding of planetary formation.

“We don’t at this stage have a good theory that tells us how planets form,” Strigari said, “so it is difficult to predict from a straight theoretical model how many of these objects might be wandering around the galaxy.”

Strigari said their approach was largely empirical. “We asked how many could there possibly be, consistent with the broad constraints, that gives us a limit to how many these objects could possibly exist.”

So, in absence of any theory that really predicts how many of these things should exist, the estimate of 100,000 times the amount of stars in the Milky Way is an upper limit.

“A lot of times in science and astronomy, in order to learn what the galaxy and universe is made of, we first have to ask questions, what is it not made of, and so you start from an upper bound of how many of these planets there could be,”Strigari said. “Maybe when our data gets better we will start reducing this limit and then we can start learning from empirical observations and start having more constrained observations that go into your theoretical models.”

In other words, Strigari said, it doesn’t mean this is the final answer, but this is the state of our knowledge right now. “It kind of quantifies our ignorance, you could say,” he said.

A good count, especially of the smaller objects, will have to wait for the next generation of big survey telescopes, especially the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope, both set to begin operation in the early 2020s.

So, where did all these potential free range planets come from? One option is that they formed like stars, directly from the collapse of interstellar gas clouds. According to Strigari some were probably ejected from solar systems. Some research has indicated that ejected planets could be rather common, as planets tend to migrate over time towards the star, and as they plow through the material left over from the solar system’s formation, any other planet between them and their star will be affected. Phil Plait explained it as, “some will shift orbit, dropping toward the star themselves, others will get flung into wide orbits, and others still will be tossed out of the system entirely.”

Don’t worry – our own solar system is stable now, but it could have happened in the past, and some research has suggested we originally started out with more planets in our solar system, but some may have been ejected.

Of course, when discussing planets, the first thing to pop into many people’s minds is if a wandering planet could be habitable.

“If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” Strigari said. Although nomad planets don’t bask in the warmth of a star, they may generate heat through internal radioactive decay and tectonic activity.

As far as a Nibiru-type wandering world in our solar system right now the answer is no. There is no evidence or scientific basis whatsoever for such a planet. If it was out there and heading towards Earth for a December 21, 2012 meetup, we would have seen it or its effects by now.

Sources: Stanford University, conversation with Louis Strigari

132 Replies to “‘Nomad’ Planets Could Outnumber Stars 100,000 to 1”

  1. I have my doubts. If there are 100,000 more rogue planets than stars, then the nearest rogue planet ought to be closer than the nearest star by a factor of (100000)^(1/3). That’s about a tenth of a light year, or a little over 6,000 AU. And that seems awfully close to me.

      1. Rogue comets should enter the inner solar system every now and then. It would just like a regular comet but moving on a hyperbolic trajectory indicating that it came from outside the Solar System. The fact that we’ve never seen one yet puts an upper limit on how common they are.

      2. Not sure if it means anything that we haven’t seen any rogue comets yet. Galactical orbits in the vicinity of our solarsystem might be stable … unless something gravitationaly changes … in which case rogue comets might turn from very rarely seen to very common.
        At least, if I imagine a circle of comets (van Oort cloud) and I change the the gravitational center towards this circle, it just becomes and elipse and finaly a hyperbole. (Unless you have 2 gravitational centers)

      3. Also remember that the difference between a hyperbolic trajectory and an eliptical trajectory with a high elipsidity can be infinitessimally small, but with large differences in effect.

        i.e. if a comet has an elipsidity of 0.999999 it would return unless otherwise affected, if it has 1.000001 it wont, again unless otherwise affected. And it would be almost impossible to determine the elipsidity with that accuracy during a single approach.

        But i also realise this is likely not the case you are refering to. One day in the future a comet should approach with a significantly e > 1.0 elipsidity.

    1. If you read the preprint you would see that Strigari et al have compared their results against the limits on interstellar comet frequency.

      1. Ouch! I should have done that too. Now I have to see how they did it.

        [But I learned some, so it was worthwhile.]

      2. Oh, it was _that_ paper. Haven’t read it yet, but p2:

        “Extrapolation down to below Earth mass scales, mmin = 10?6M?, yields
        ? 10, and further extrapolation down to mmin = 10?8M? yields ? 60. Intriguingly for a continuous power law extrapolation down to ? 10?15M?, the number of nomads per star approaches the bound on the abundance of interstellar comets”.

        So they are not only safe for now, they are exactly compatible.

        I still think that is an overestimate of the real population at those sizes, but that isn’t what they are trying to do here.

        Hmm, does that mean Oort cloud migrants are more stressing observations than the nomad population?

    2. Good idea! That seems to be the more stringent limit.

      But it seems a lot fuzzier to make an estimate from that. Strigari put brown dwarf analogues, collapse objects, in there (which at the moment doesn’t seem to be a viable pathway for smaller planets in protoplanetary disks, IIRC). But I doubt you form comets out of that.

      So perhaps comets are more constrained to the number of stars than Strigari’s objects. And then you have to consider how the evaporative cooling of initially hot protoplanetary disks set up the Oort cloud. I didn’t know this, but estimates say most initial ‘evaporites’ are destroyed by collisions on their way out. After that, an amazing ~ 90 % of comets could be exchanged between stars in clusters. (That was ~ 10 % last time I checked, IIRC.)

      Still a lot of comets. If the typical Oort cloud contains ~ 5 Earth masses of comets (and according to yesterday’s news we can now bound our protoplanetary system size to at most 80 au against an average ~ 60 au) or ~ 3*10^25 kg and the typical comet is ~ 1 km in diameter or ~ 3*10^14 kg @ ~ 0.6 kg/dm^3 density, we have ~ 10^9 of them exchanged for every Oort cloud.

      They would outnumber the planet limit by ~ 10^4, or compared to your distance estimate we would have one hyperbolic trajectory comet for every 5*10^-2 ly or ~ 300 au. If we look from a cometary (roughly the stellar neighborhood) rest frame, the solar system travels ~ 20 km/s or ~ 4 au/year (sez Google).

      We would see migrant comets at a rate of ~ 0.01/year.

      At a frequency of ~ 800 individual comets over 300 years, we observe comets at a rate of ~ 3/year.

      For every migrant, which we would see once every century at most, we would see ~ 300 “own” comets.

      If we never have seen a hyperbolic trajectory comet for ~ 300 years of continued observation, it seems some of those numbers would have to give a bit soon. (Someone would have to do a proper statistical test for significance.)

      Yes, what I can see your idea is more stringent. You should maybe try to publish that. But the new exoplanet limit seems fairly safe for now, as you can squeeze it in by polishing the fuzzy numbers.

      1. Nice quickie analysis Torbjorn! Of course I do wonder what the probability of interstellar comet encounter limit is and just how close the impact parameter has to be for the comet to be sufficiently accurately observed. With a hyperbolic velocity of 20 km/s that means there’s not much gravitational focussing of the comets outside Jupiter’s orbit. If we assume a “capture zone” around the Sun of 3 AU, then the Sun sweeps through about pi*3^2*4.5 AU^3/year = 127 AU^3/year. There’s 253 trillion cubic AU in a cubic light year, which means 6.6 billion comets could be stashed in it and we’d have even odds of seeing 1 in 300 years of observing. As there’s 1 star per 200 cubic light years, then free comets could out-number stars 100 billion to 1 and we’d be none the wiser.

      2. Seems my limits are even more stringent than this estimate from 2004…


        Given the amount of sky covered by Spacewatch observations, and the detection efficiency for objects as a function of their rates of motion and apparent magnitude, we determined the 97% upper confidence limit on the number of ISOs as a function of the slope parameter ? . We have parameterized the number density of ISOs as ? =? o 10alpha(H-Ho), where H is the absolute magnitude of an object, ? is the slope of the number density as a function of H, and ? o is the space density at Ho. We use Ho=19.1 which corresponds to an ˜1 km diameter object with a typical cometary albedo of p=0.04.

        At ? = 0.5, corresponding roughly to the expected slope for accreting planetesimals, the 97% upper C.L. on the number density of ISOs is ˜ 1014 pc-3 or ˜ 10-2 AU-3. Spacewatch is supported by grants from NASA’s Near-Earth Object Observation and Planetary Astronomy Programs, the U.S. Air Force Office of Scientific Research, the Paul G. Allen Charitable Foundation, and the Brinson Foundation. B. Meinke’s research was supported by the NSF REU Program at the IfA, summer 2004.

      3. Another estimate, with a quite different outcome, suggests significantly lower numbers of interstellar comets is this one by Jura…
        Title: An Upper Bound to the Space Density of Interstellar Comets
        Authors: Jura, M.
        Publication: The Astronomical Journal, Volume 141, Issue 5, article id. 155 (2011).
        Two well-studied white dwarfs with helium-dominated atmospheres (DBs) each possess less hydrogen than carried by a single average-mass comet. Plausibly, the wind rates from these stars are low enough that most accreted hydrogen remains with the star. If so, and presuming their nominal effective temperatures, then these DBs have faced minimal impact by interstellar comets during their 50 Myr cooling age; interstellar iceballs with radii between 10 m and 2 km contain less than 1% of all interstellar oxygen. This analysis suggests that most stars do not produce comets at the rate predicted by “optimistic” scenarios for the formation of the Oort Cloud.

    3. After that first, long comment I realize a curious question is, why haven’t our star captured migrant planets? (Or have we, maybe some moons can be explained that way?)

      What is the capture probability?

  2. Isn’t it nice that such limits make sense now? I wonder if people bothered with them before there were known to be exoplanets at all.

    The analogous situation now is of course limits on how many biospheres there are. Potentially at least as many as those wanderers, for every Neptune gas giant we can have a few Europa ice moons. But see above.

    1. You mean you don’t believe someone (Nancy Lieder) who believes she was contacted by aliens about a rogue planet over astronomers? Shocking.

    2. Ah now that you bring that up, Niburu and Dollyworld can be shown to have caused the mess we got here,,,,,,,just saying.

  3. Did anyone else here wonder what bearing all this might have on supposed dark matter estimates?

    A while back there was this about red dwarfs being far more abundant in galaxies outside our own and therefore possibly changing dramatically our understanding of cosmic galactic evolution:

    Neither this article nor the UT one about the red dwarfs makes mention of the possible implications that perhaps we have an ‘aaah ha!’ moment where we found more of the missing matter.. There have been quite a few of these type of discoveries over the years…
    Here’s a few more..


    I realise there is still the question of the halos but it does seem we seem to be discovering a heck of a lot of unaccounted for matter within our own and other galaxies recently…

    Is it just me or are we possibly staring at the ‘dark’ elephant in the room?

    1. my thoughts exactly. i wonder if they used the dark matter mass estimate to extrapolate the number. as in: the only reason it’s dark is that we can’t see it yet. below current instrumentation’s detection thresholds.

      sub stellar WIMPS?

    2. I was going to write about just this last night, but decided to head to bed instead. There are two things to consider. At a ratio of 100,000:1 rogue planets to stars this would almost double the amount of ordinary matter in the galaxy. By extension this would carry over to the entire universe. This also changes our physics of nucleosynthesis, for this would significantly increase the amount of atomic elements with atomic number n > 2.


      1. Hi LC;

        I’m not sure if you’ve heard of Andreas Tziolas. He’s involved with Project Icarus. He seems to think that the Fresnel Lens and solar sail system is not an appropriate solution for an interstellar probe. If you have time could you weigh in here?


        Apologies, I tried to find an email address for Lawrence B. Crowell. but was a little unsuccessful.

        This is a little off topic (will remove this comment later)

    3. I’m not an expert on this, but I don’t think it’s an out-of-nowhere matter. It’s an expected or missing matter. So, it doesn’t have to be like that that there is suddenly twice as much matter.

      That would make it 18% of dark matter and 8% of ordinary matter at best. I don’t think it’s about elephants. 😀

    4. The amount of matter in stars is about a factor of 7 times *less* than there is in gas (and most of this gas is between galaxies not inside them.) So even if they doubled the amount of matter we think resides in stars and planets, they’ve only incrementally changed the balance within normal matter between gas and stars. Dark matter out -weighs normal matter by a factor of 5 (a result from WMAP – an experiment that measures the cosmic microwave background, also consistent with deuterium constraints on the production of elements during primordial nucleosynthesis), and dark matter outweighs the stars by a factor of 35 or so. So no, even if there are this many (and remember that’s an outside upper limit estimate), these planets cannot be the culprit for that elusive dark matter. They’re dark enough, for sure, but there is too few of them.

      1. This might depend upon the average mass of these rogue planets. If most of these are gas giants this could increase this mass portion considerably. I do agree that even if that were the case the amount of ordinary matter in the universe would probably increase by a fraction of a percent less than 1%.


      2. Thank you Megan – Great response and very good information which really answered some questions I had in my mind.


        Subject: [universetoday] Re: ‘Nomad’ Planets Could Outnumber Stars 100,000 to 1

  4. I’m confused. How is it that we can detect rogue planets 10 – 20k light years away, when we have trouble detecting planets only a few 10’s/100’s of light years away around neighbouring stars? I would imagine that these planets are extremely faint and space is really, really, really big, so how do we know where to find them? Is microlensing that good?

    1. Is it dozen of Jupiters too many and too small? I don’t think so. Then, you can use statistics to extrapolate.

      Kepler doesn’t have a trouble detecting planets several 1000 ly away, there are lots of candidates, it’s just a problem to confirm them, it takes a time and also available telescope time.

      1. Ok, but Kepler has the advantage of knowing where the planets are – it just gets pointed at the known stars in the region. Furthermore, Kepler doesn’t actually see the planets, it just looks at the effects of the planets on the stars, as does every other planet finding technique (i.e. looking for the wobble or the dimming of the star). Rogue planets aren’t orbiting stars. How do the astronomers find rogue planets when they are incredibly faint and so far away? How do they know where to look? This article and the previous one about finding the rogue planets doesn’t have that info. I’m just curious, I’m not questioning whether they found them.

      2. There were articles about microlensing on UT. They use foreground and background star. I think Ivanman even posted a nice graphic description, but that was long time ago. Lately, I remember something about around 3000 cases where both stars are in line from our point of view and only around 400 microlensing effects were usable. I hope I don’t mix it with something else. :d

    2. Kepler’s field of observation is the constellations Cygnus, Lyra and Draco..

      As constellations are generally asterisms which are groupings of stars at disperate and varying distances, I will provide the estimates of the brightest starts in each Constellation (Cygnus, Lyra, Draco, respectively from wikipedia):

      ~1,340-1,840 ly (Deneb), 25 ly (Vega), 154.3 ly(Gamma Draconis).

      The Kepler space observatory uses only a photometer employing the transit method to observe when planets pass in front of their host stars.

      It used to be said the transit method was unsuitable for detecting earth size candidates. However, this was only true for ground-based telescopes (not space-based observatories like Kepler).

      It really amazes me that the smallest candidate detected by the Cal-Tech team using Kepler to date is the size of Mars!


      To date, ground-based observation campaigns have relied on gravitational microlensing to detect earth-mass planets, brown dwarfs and rogue planets.

      To my limited understanding the reason that rogue planets have thus far only been detected by earth-based microlensing (as opposed to other detection methods) is that planetary binary lensing in the foreground galactic bulge is necessary to squeeze out the tiny blip in the light curve necessary to detect the rogues. Apparently planetary binaries are quite rare so I deduce extrapolation was used to deduce estimates of rogue population based on our current understanding of stellar and planetary evolution.
      -further reading about ground-based micro-lensing detection technique at:

  5. “Men will faint from terror, apprehensive of what is coming on the world, for the heavenly bodies will be shaken”……Luke 21:26….could this have a literal meaning?

    1. I seriously doubt it. When in the middle of an earthquake, any “Heavenly” body observable at the time would appear to shake. Remember: The Bible was written by unsophisticated people trying to make sense of the world around them, with the added factor of asserting control over their compatriots.

      1. Who said anything about an earthquake? By the way, the people of the bible were not unsophisticated.

      2. They were unsophisticated compared to the scientific norms of today. Uneducated, nomads with no appreciation of science is a fair definition of “unsophistication” compared to today. There is a difference between sophistication, and having a working knowledge of science. My comment about earthquakes : if you have ever been in the midst of an earthquake, the heavens do seem to move or shake if you happen to have the presence-of-mind to look up. However I think anything I may say will fall on deaf ears. Fundamentalists of any faith tend to ignore facts not in sync with their brand of superstition. Good luck with your faith when your time come to meet the whatever.

      3. As for the structures of antiquity: fairly basic math and brute strength explains this. You keep referring to bible verses as if the were words from on high. I disagree with this, and repeat my earlier contention that they (Biblical writings) are the product of a people trying to understand their universe just as we are today. That these fables have any relevance today is ludicrous. However I bow to your faith without agreeing with you or it.

      4. ahhh yes, the simpleton view of modern man…they used brute force. It’s clear you don’t know much about history….you also ignored my suggestion of reading the link I sent you.

      5. Actually I majored in History you sanctimonious twit. Also,I checked out that link. BTW. It was a bunch of blather by pseudo intellectuals, making a common,(or purposeful) mistake on the use of a word with several meanings. Are you really that stupid? Grow up Jr. and get an education.

      6. Your education didn’t include the art of manners or how to discuss an issue. You sound more like someone still in jr high. Come back when you’ve learned some manners.

      7. Boo!

        Your original statements have nothing to do with this story, and all you do is act like some religious nutter hell bent to inflicted and peddle their extremist religious wares.

        Pretending to hold some moral high-ground when you say little of any intelligence or importance just makes you an irrelevant twit.

        (Just reading your putrid views and bigotry especially against those contracting HIV/ Aids and homosexuality shows your lack of education or decency.)

        Why bother with filth like you!


      8. Why would I treat you civilly when you have started this “Flame” Fest? You are a troll of the basest sort: one that uses faith as fact when you know your precepts are not based on fact, but upon superstition and dogma that has been shown to be false at every step in the advance of Human endeavors. You are a sad benighted pitiful excuse for person. Go Away and bother no one again. Or better yet: Seeing that your head is firmly ensconced in your rectum, I suggest that you JUMP very high and hopefully disappear into the singularity of your soul. We will place your picture on a milk carton! (maybe)

    2. Aw please!

      Sirach 40:11 “All that is of earth returns to earth, and what is from above returns above.”

      Contradiction is everywhere, even in the Bible!

      So literally, which is it?

      1. Meaning what exactly?
        Your comment has absolutely nothing to do with anything expect for some insane wish to inflict you Biblical claptrap on others. Evolution should have weeded people like you out long ago!

      2. Some people just can’t carry on a discussion because they haven’t the intelligence to think before they speak.

  6. Are these planets a viable candidate for the “Dark Matter” that some hypothesize makes up the majority of matter in the universe?

    1. See my response to Wezley Jackson above – short version is that even if there is that many planets, they can’t explain the dark matter that holds galaxies and clusters of galaxies together. It might slightly rearrange the balance between gas, stars, and planets, but doesn’t change the total amount, which we know from other experiments.

      1. Thanks Megan, I have not the background, or the math to even comprehend these things,except on the awesome scale that I find here some days. I am a historian, not a astrophysicist. However, the Cosmos are a great mystery and a joy for my contemplation. Sites like this one help people like me understand a bit more clearly our place in the Grand scheme. (even though we haven’t got it quite figured out yet) My Idea of Heaven would be to venture between the Galaxies and watch the birth and death of stars, and the interactions of all matter. Mystical? You bet!

  7. I wonder if this (how these finding, assuming they are supported by further research) might be a subject for an Astronomy Cast episode? What is the estimated total mass of the rogue planets vs. that estimated for Dark Matter? (that term always conjures up thoughts of thecharacter in the Buzz Lightyear cartoon series 🙂 )

  8. have we ever witnessed one of our own comets go interstellar? i mean have we ever witnessed an encounter with jupiter or saturn where a comet was launched into escape velocity?

  9. So with 100,000 x the number of planets as suns, and 1/100.000 the mass of an average sun for each planet (average being something like Earth) that puts us at the same mass as the stars in the galaxy…which still falls way short of being in the dark matter mass category of 3 x as much as baryonic matter….although it tightens the gap significantly.

    1. yes indeed,,,, Science Fiction = Science Prophecy. there are other Prophetic stories about lonely planets twirling about the cosmos. Even some instances where they are quite warm enough for life. Need proof,,,,,,,,, see Icon to left.

  10. Is there anyway for them to know if any of these planets are close to us, and how would we know? How close would they have to be for us to detect them?

    1. If it is as large diameter as Jupiter we would easily be able to spot it if it was 100 times further out than Pluto, using something called telescopes, and if it was on a trajectory to the inner solarsystem it would possibly arrive in a few hundred years from when we first detected it.

      Again, I simply have to guess what your real question is.

    2. Perhaps you can find a Biblical quote or divine providence that answers your question?
      Obviously none of us are capable enough or smart enough to answer you.

    1. It was actually me and a bunch of my friends who prayed to The Flying Spaghetti Monster that he would go back in time and make it look that way. And some say prayer doesnt work… *pffft*

      1. Please come back when you can actually answer a question. For being a site on science, the discussion quickly degrades to jr high level.

      2. I would say the same thing to you: Please come back when you actually have a scientific question and a scientific discussion in mind. And not a hidden agenda to sneak in the bible and religion pretending that you have a science question.

        If you want to debate religion and science, then go to religious sites.

      3. My appologies. From your tone in other posts in this forum i assumed that your intent here was not to ask for scientific answers, but only to question the openmindedness of others and insert the biblical explanations into anything that allowed an opportunity. I assumed you had an agenda including trying to promote biblical explanations.

        However, you didnt actually ask for an explanation, and your linked image is not accessible for everyone to view, so its not really possible to answer your non-question.

      4. And what is the proposed link between Uranus being tilted 98 degrees (wich i again have to assume being what you are referring to, because again you dont really ask a question), and this article?

        Unless you ask specific questions, you cannot get specific answers.

      5. The reason for Uranus’s unusual axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth sized protoplanet collided with Uranus, causing the skewed orientation.

      6. That is one possibility yes, likely the collision was actually a merger of two bodies who ended up forming the tilted Uranus.

        However, that is still merely possibilities, or speculation.

      7. What has this and the 98 degree angle of Uranus to do with Nomad planets?

        Maybe you should start by calculating the energy it would require to rotate Uranus.

        Second you should give a scientifically explanation how a collision could tilt Uranus like this. How much mass does it lose, how does it’s orbit change, what happens to the the object scientifically. How long ago did this happen… (And scientifically means no religious texts or Mayan references or so)

        What makes you think that a moon would survive a collision? Maybe you should start giving scientifically calculations how much energy gets involved with such a collision. Just to check if that moon would not get vaporized completely.

        Ever heard about Universe Sandbox? Well get that program and create a convincing simulation how such a collision could happen.

      8. You know, you might want to actually pick up a friggen book and learn to READ!!!

        “The reason for Uranus’s unusual axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth sized protoplanet collided with Uranus, causing the skewed orientation.”

      9. I want to know what YOU know.

        And during the formation of the solar system is about 4.5 billion years ago. No external nomad planet is required.

      10. Good advice, you might want to follow that advice yourself sometime, perhaps read more real sciencebooks.

        It is speculation, albeit scientific speculation, but it is not a scientific fact.

      11. This is true. It was formed when the Solar System was formed. The Earth was formed by smaller bodies that were accumulated to form the planet. A collision of a Mars-sized body with the Earth likely formed the Moon. However this happened 4.3 billion years ago, and the planet formation accretion ended after a few million years.
        This story is about rouge planets roaming outside our solar system. Due to the vastness of space, the probability of one colliding with one of the planets is next to zero.

        If this was your point, then you should have said so in the beginning. (I think you have gone on a internet search to find anything to support your crazy earlier arguments.)

        I still think you are being deliberately disingenuous, pretending to avoid direct scrutiny.

      12. Uranus is completely irrelevant to this story, dopey. How can you answer it when the question is silly and meaningless.

        Where do you get off here, eh? You come up with some irrelevant biblical quote, acting like some smarty to stir up trouble, then your all miffed because people have rejected you as a complete fool.

        If you are searching for religious validation here, you haven’t come to a place that will appease you for your own ego.

        Really. *pffft* is exactly the response you deserve! Deal with it!

  11. This whole story appears a little bit over-hyped.
    The catch is the high number of 100 000 nomads per star.
    But if you look carefully this number mostly results from y maximally steep extrapolation to low masses. The high number would be dominated by low end mass objects. The overall mass in such objects woud stay limited.
    Overall you can compare to a scenario, that most stars are created with several planets – number largely depending on the lower bound of mass considered.
    A large fraction of these gets lost to become free nomads.
    Only the high mass end is a downward extrapolation of brown dwarfs. I remember earlier investigations indicating a gap between these populations.

    When using the exponential slope alpha =2 leading to the high number 100 00 for extrapolating (dwarf) planetary objects in the solar system, there would be many still to be detected, even considering some loss. Compared to the distribution in the Solar system (which may not be representative) the parameter appears rather high – and anyway it’s an upper bound. Already a slightly lower alpha would significantly reduce the number of nomads.

    Regarding remarks to nomads hosting bacteria: obviously this kind of consideration is meanwhile obligatory – ok. But the speculations on transport of life in this way are quite far fetched. I neither see a significant probability, that such propagation would work, nor that it would help to explain something. Life would be far less likely to originate on energy starving nomads, than on planets.

    1. The southern hemisphere of Mars has numerous impact craters, while the northern hemisphere does not. ….whatever happen to that moon, had happened to Mars at the same time…it might also explain the difference between the light and dark sides of the moon.

      1. John,

        If you are unable to ask a proper question, then it is not possible to answer them. And I have have followup questions to your questions that I need to know in order to properly answer/correct you, can you answer my followups?

      2. Uranus being tilted 98 degrees and Venus rotating backwards. Why couldn’t all of these events have happened at the same time….an outside planet passing through. Is this too hard to understand?

      3. If they are unrelated, and there is more indications of that than the contrary, then there is no reason to assume the events are related.

        Is it possible that this is completely unrelated events?

      4. Why would an outside planet passing through that hits Uranus even survive the impact and even get a trajectory near Venus?

        Even then you claim that an Earth sized planet (probably referring to an Earth mass planet, not the same chemical composition) hits Uranus. How could such a small object reverse the rotation of Venus which has the same mass?

        I am interested to see how the orbit of such a Earth mass planet would need to be on order to make it change the rotation of Uranus this way. This type of orbit would not even be in the plane of the planets and thus never make it getting near any other planets.

      5. Because the only theory for Uranus being on it’s side…it was hit by something. That could explain the scraps on one of its moons. There could been more then on planet passing trough. It wouldn’t have had to his Venus, only pass close to it.

      6. Actually when you see how Uranus is tilted then there is no way that the surviving object or shrapnel would even come near the other solar systems objects. It would have about a 90 degree angle perpetual to the plane of the orbits.

        Also coming close to Venus cannot change the orientation. You need a physical collision.

      7. I agree with magnus.nyborg, what makes you think this happened at the same time?

        Also can you give a “scientific” correct orbit that includes the events that happened? And I am not referring to a made up route, I want to see some calculations what speed what position what planet had. How much energy gets gained or lost for every object?

        Instead of moving the goalpost, start with something simple. How much energy does it take to rotate Uranus axis? Then we can determine what mechanism could do such a thing.

      8. I asked some simple questions….COULD all of these events have happened at the same time? Has ANYONE ran a model going back in time to track the position of each planet?

      9. It is IMPOSSIBLE to run a simulation back to the beginning of the solar system, simply because anything unknown will affect the simulation.

      10. Where did I say the simulation had to be run back to the beginning of the solar system? I said..run one back to see if there’s a point where all the planets and moon, could have been facing the same way…like reconstructing an accident.

      11. The furthest simlations have run with correlating error-analysis is approximately 60 million years back, but the errors/uncertainties increase rapidly.

        And the answer to this question is NO.

      12. So you think that “facing the same way” must proof that the events are connected?

        First of all, planets moons move. Anything affecting one planet would take time before it could affect another planet. This could be millions of years in between. So facing the same way is baseless.

        Second do you have proof that the events have the same time table?

        It is your job to provide the reconstruction of the accident. It is your job to show that an object hitting one planet, could actually move in a closer orbit to hit another moon/planet.

        It is your job to provide evidence that when a Earth sized object hits Uranus, that it can survive the collision and actually move towards the inner planets and not get ejected outside the solar system.
        You should be able to give the incoming collision vector, mass, speeds when the collision happens at Uranus.

      13. I suspect he is going for that an explosive event caused craters etc throughout the solarsystem, but that he fails to realise that even if one big explosive event happened, it would not instantaneously affect all other bodies – perhaps he doesnt even realise the distances involved here (several of his questions indicate this).

        Whenever somone starts a question with “Why cant it be this way?” and ask a silly question, you know they havent thought it through properly.

        I am also suspecting that his questions are related to PlanetX/Niburu and that he is merely fishing for some confirmations.

        John, if you read this – PlanetX is complete bullshit! Everything claimed so far about it is complete bullshit, and even if there would be a big planet somewhere close to the solarsystem, it isnt the claimed PlanetX.

      14. Sadly for him, Nibiru would be 1.8 times the diameter of Jupiter and around 4 AU from the Sun right now. If it is not at 4 AU then it is not Nibiru.

      15. …and it would be brighter than jupiter is now, not only clearly visible with the unaided eye, but one of the brightest objects in the nightsky. Unless ofc it was hiding behind something, playing peek-a-boo… 😛

      16. So you are stating that you have no scientific evidence that those events happened at the same time?

      17. Eh? The entire moon’s surface has about 14 days of sunlight and 14 days of darkness each lunar month. 50% of the moon is illuminated at any one time. Almost 100% of the moon sees sunlight once per lunar month

        What has impact craters have to do with the position of the sun as observed from the moon? There is no relationship.

        What has the distribution of craters on Mars have to do with the craters on the moon? From your quite illogical arguments and inferences here, you really show you don’t know what you are saying!

        Frankly, your absolute desperation to be heard (when you’ve already now been dealt out of the game) is filled now with more nonsensical nonsense.

      18. There is no light and dark side of the moon that is fixed. Every area is 14 days lit and 14 days dark.

      19. OMG…you can’t even understand a simple question. The moon does NOT rotate…it shows one side to US…WE call the other side..the DARK SIDE.

      20. Since the moon is always showing the same side to the earth, how can it anything but rotate around its axis once every month??

        The moon has a month long DAY where half is in darkness, half is in sunshine, and you have now shown your complete ignorance.

      21. Actually, the moon has a near side and a far side.

        The rotation of the moon is just the same as the orbital period around the Earth, which has been locked in by the mutual gravitational pull between the Earth and Moon.

        Again you haven’t ask a question. (where is the question mark, eh?)

        You have made a general statement that is really just a supposition, and has many wrong assumptions. Where is the scientific evidence for this?

        Seriously. It is all hearsay and is not at all science.

      22. At least we now know why the coward ran away!

        He said; “I’ll come back later and see if there’s any intelligence on here.”

        I’d guess he will never come back, then!

    2. also….Uranus being tilted 98 degrees and Venus rotating backwards. Why couldn’t all of these events have happened at the same time….an outside planet passing through.

      1. ….because it didn’t.

        Are you Immanuel Velikovsky’s love child?

        Velikovsky was a Old Testament proponent who thought planetary collisions could explain the Exodus in the Bible.

        This now explains your mumbo-jumbo here.

        I found one quote that is pertinent here by Leroy Ellenberger, who once said;

        “The less one knows about science, the more plausible Velikovsky’s scenario appears….”

        You have just proved this proposition 110%!

    3. It would be interesting to see, if someone with a computer, could figure out the rotations and the orbits going back in time…to see if there’s a point where all of these planets and moons with the damages, were facing the same way, when the damages happened. Like recreating an accident.

      1. Why not arrange for that computer simluation to be done, and get back to us with the results when it is done?

      2. They have. Nothing significant has really happened for billions of years, and certainly nothing in the last 6000 years!

        Just an educated guess, but I’d assume you think the Earth was created around 4000BC, like most the right-wing anti-science American Fundamentalist christian lobby.

        Frankly, the accident here, is you must have had your common sense beaten out of you as a child. Shame. (San Diego, they say?)

      3. It’s clear you haven’t a clue in what you say. Questions? Do you know how it put a question or even comprehend a simply reply?

        I.e. “They have. Nothing significant has really happened for billions of years, and certainly nothing in the last 6000 years!”

    4. What makes you assume these are ‘dark planets’?

      They are planets, if nothing is shining upon them they will be dark – if something IS shining on them, they will reflect some portion of the light and might even look bright.

      And what kind of answer are you expecting? Yes – No – Maybe – Possibly – Probably?

  12. This question has also been ignored…Is there anyway for them to know if any of these planets are close to us, and how would we know? How close would they have to be for us to detect them?

    1. I answered your question below (as far as I could as it is again not a specific question).

      Is that answer satisfactory to you, or do you want to ask a more precise question?

  13. This site appears to be full of jr high schoolers and lower on here. Sad, except for a few post (M_Malenfant and Peristroika, for example) …the rest are just plain ignorant.

    1. Wow,

      Did you even stop to consider that it is you who are the problem here?

      Anyway, you post has nothing to do with the article and i am going to ask the moderators to remove it.

      1. Yes, I agree. johnb123 seems to be fascinated with middle school. Read his other posts. He is either a 7th grade student, or a brain dead fundamentalist trapped in the books of the old testament. Why he would wish to troll a site such as this one is beyond me.

  14. I think it’s best if most replies from this site go directly into my trash…I’ll come back later and see if there’s any intelligence on here.

    1. I lolled loudly when you said that one side of the Moon is always in darkness! ANY intelligent person would understand that the Moon rotates around its axis once every month, by necessity, and therefor every part of the moon has an approximate 14 day long DAY and a 14 day long NIGHT (except the poles).

      I realise that you simply do not understand why your questions is nonsensical, and why they trigger responses that you do not understand either, but enough is enough. This is not a kindergarten place where you can ask questions that are trivial to answer yourself if you put in atleast some effort.

    2. The thing that really cheese me off here is your obvious contempt for people who dare to stand up to you or don’t agree with your quite insane worldview. Sure. You are entitled to your religious beliefs, but you are absolutely not entitled to shove them down everybody’s throats!

      It is clear you deliberately came here to make comments just to try and validate some wacky personal notions or distorted dogma that supports your apparent twisted religious faith.

      What is really funny, is every time someone replies to you, they are either; “trash”, “plain ignorant”, “full of jr high schoolers” or have a “non-thinking reply.” What you really mean is that anyone who doesn’t agree with you is just slapped with the hand of denouncement – a trick often used by religious zealots to exert some authority or the wrath of god over their downtrodden subordinates. So instead of honestly facing your own obvious limitations and knowledge, all you can do is brush off those who have pointed out your own obvious failings.

      Frankly, you’ve just been caught with your pants down, sunshine.

  15. I can simplify the question a bit. Judging from what we have observed about exoplanet systems and our own, it is unlikley that more than a few Jupiter masses of planets would be ejected by any planetary system after its formation around a star. The only way to get a large planet to star ratio is if protostellar clouds form planet sized objects more frequently than stars. In other words what is the lower mass/density limit that a protostellar cloud can reach, and how frequently does it get there relative to the stellar mass objects we can see more easily? From observations it would seem that a collapse producing brown a dwarf sized object is fairly common. From theory we know that the fragmentation of a progenitor cloud into various sized stellar embryos is a rather chaotic process highly dependant on local conditions. I would then surmise that there would be a more even distribution of embryo sizes rather than a parabolic curve favoring a predominance smaller sized embryos. With regards to this question infra-red observations are going to be very helpful in establishing the lower size limit and frequency of such embryos, and we just so happen to have such instruments on-line now and in the near future to provide us with helpful data.

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