BY ANY OTHER NAME: A new study finds that numerous planet-mass objects could be wandering freely through the galaxy. Above, an artist's depiction of one such world.
Image: NASA/JPL-Caltech/R. Hurt
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Pluto, please step aside. The beleaguered world has for the past several years been at the center of the debate about what defines a planet. Now a new crop of astronomical objects has arrived to further cloud the matter.
The Pluto issue was formally resolved in 2006, when the International Astronomical Union (IAU) relegated Pluto and its diminutive ilk to dwarf planet status. (The conversation has not stopped, however; among a number of recent Pluto-centric books are titles like The Case for Pluto and How I Killed Pluto and Why It Had It Coming.)
Outside the solar system the issue is less clear—what distinguishes a star from a brown dwarf, which is a sort of failed star not massive enough to burn hydrogen in fusion reactions? What distinguishes a brown dwarf from a planet? And now, most puzzling of all, what to call an object that seems too small to be anything other than a planet but that floats freely through interstellar space rather than orbits a star? Such objects are numerous in the galaxy, and possibly more numerous than ordinary stars, a new study concludes.
Two astronomical collaborations report in the May 19 Nature that they have located a population of 10 celestial objects, each with about the mass of Jupiter, with no detectable host star. (Scientific American is part of Nature Publishing Group.) By extrapolation, the study's authors, from the Microlensing Observations in Astrophysics (MOA) collaboration and the Optical Gravitational Lensing Experiment (OGLE) collaboration, calculate that there should be almost twice as many such objects in the Milky Way as there are stars. Some of the newfound objects may simply orbit a star at a distance so great that their host star is not apparent, but the researchers estimate that most of them are indeed free-floating.
"This is a pretty remarkable claim," says astronomer Mark McCaughrean of the European Space Agency. And it will no doubt undergo close scrutiny. But if the interpretation proves correct, a future NASA mission could turn up such free-floating bodies in droves. A planned spaceborne observatory called the Wide-Field Infrared Survey Telescope (WFIRST) should be able to discover 1,000 such objects, says study co-author Takahiro Sumi of Osaka University in Japan, a member the MOA group.
Other researchers have expressed cautious enthusiasm about the research. "This is a very exciting discovery, but still it has to be confirmed by other teams, other techniques, more statistics and so on," says Joachim Wambsganss of the University of Heidelberg in Germany, who wrote a commentary accompanying the research in Nature. "It's plausible" that these planetlike objects are indeed adrift in the galaxy rather than simply loosely bound to a star, Wambsganss says. "I wouldn't say it's proved. I wouldn't bet my house on it, let me put it this way, but it's pretty convincing."
Microlenses for Macro Objects
MOA and OGLE look for so-called microlensing events in the night sky. Microlensing occurs when a chance alignment brings an otherwise unseen celestial object between Earth and a distant background star. The celestial object's mass bends light rays from the background star, focusing the light like a magnifying lens toward Earth and making the background star appear temporarily brighter. Those events are rare, so microlensing searches monitor large numbers of stars for long periods of time; the new discovery came out of a MOA survey of 50 million stars in 2006 and 2007.
The duration of a microlensing event indicates the mass of the celestial object that acts as the lens. The MOA group found 10 microlensing events that lasted less than two days, which points to a lens of at most a few times Jupiter's mass. The independent OGLE group broadly confirmed that finding. But none of the objects were accompanied by a stronger lensing signal indicating a more massive host star nearby. So either the objects are drifting alone through the galaxy or they orbit their stars at a great remove. But there seem to be far more of these objects than can be explained by wide-orbit planets, and also far more than can be explained by very lightweight stars or brown dwarfs.
The researchers speculate that these newfound objects may have formed in relatively ordinary planetary systems before losing a game of gravitational tug-of-war with sibling planets and being flung clear of their birthplaces. "This implies that star formation must be producing many planets that are ejected away from their star," says Pavel Kroupa of the University of Bonn in Germany. Those ejections, Kroupa says, could even be caused by nearby stars perturbing a planetary system. "Clearly any theory of star formation will need to account for this population of free-floating planetary-mass objects," he adds.
Planet or Dwarf?
Free-floating objects in the planetary-mass range have been found before, but they were located in star-forming regions of the galaxy and had a bit more heft than the newfound objects. That led some astronomers to think of them as being more akin to lightweight brown dwarfs than to planets—that is, they probably formed on their own rather than in orbit around a larger parent body. But the newfound objects seem to be solidly in the planetary-mass range and also seem to dot the galaxy, not confining themselves to regions where stars and failed stars such as brown dwarfs are being born.
As to what to call these newfound objects, Wambsganss favors brevity. "I think the most intuitive name is 'free-floating planets,' but if we decide to adopt that name then we have to give up one of our definitions of a planet," he says. "A free-floating planet is a contradiction, because a planet is by definition bound" in an orbit around a star.
That contradiction will no doubt fuel controversy—McCaughrean calls "free-floating planets," a term that appears once in the new study, "a red rag to a bull." Even the more conservative "free-floating planetary-mass objects" can be misleading, McCaughrean says. "To me, that's somewhat still equivalent to calling a Chihuahua a 'cat-massed object,'" he says.
Sumi predicts that his and his colleagues' new discovery will spur discussion at the IAU, much like the 2006 debate that led to Pluto's demotion. "I think that people have not thought seriously about this yet because there is little evidence of these objects so far," he says. So what is Sumi's take? If a celestial object formed just like any other planet, which he and his colleagues suspect is the case for their newfound objects, then he says "it is natural to be called a planet."
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76 Comments
Add Commentmaybe its not "free-floating planets",
Reply | Report Abuse | Link to thismaybe some kind of advance spaceships.
My vote is Vagi. Latin for wandering.
Reply | Report Abuse | Link to thisby your definition earth is a spaceship trapped in a gravitational field around the sun... ok I can live with that.
Reply | Report Abuse | Link to thisthey r not revolving around any sun (star).
Reply | Report Abuse | Link to thisI've often wondered about this. The same forces that keep planets in orderly orbits can also eject planets into deep space. How cool would it be to explore a planetoid from deep space as it just passes through our solar system?
Reply | Report Abuse | Link to thisMAVERICKS
Reply | Report Abuse | Link to thisWhat would happen if our sun attracted one of these mavericks into its orbit?
In fact, that's a good name for them, mavericks.
Couldn't galaxies colliding (as they say Andromeda will be doing with the Milky Way in a couple billion years) lead to this sort of thing?
Reply | Report Abuse | Link to thisHow about we call them UQBs (you-qu-bees), for Unbound Quasi-planetary Bodies.
Reply | Report Abuse | Link to thisIt's kind of mind boggling that until recently the pervasive question was always the same, "Are we alone?". It was almost rhetorical. Yet, so quickly we have come to discover that there are lots and lots of planets all over the place, many being in the habitable zone around stars. And now planets are even being found in free fall within our galaxy. It won't be much longer. We are not alone.
Reply | Report Abuse | Link to thisWell seems like they'll need to revisit the definition of planet again. To work it should be based only on mass range and shape.
Reply | Report Abuse | Link to thisthat would be awesome
Reply | Report Abuse | Link to thisWe may not be alone, but it's not just whether life exists on other planets--it's whether that life is at roughly the same stage of evolution/development we are. Which is highly unlikely. Think about how long the Earth has been around. Now think about how long our history dates back. Yeah.
Reply | Report Abuse | Link to thisHow about Free Ranging Planets,or better still,Gravitionally Released Planets.
Reply | Report Abuse | Link to thisWhen a very large star goes Supernova, as much as 90% of its mass is blown out into space.It follows that any massive planet orbiting that star would also be thrown out into space since the mass of the star is now a small fraction of what it was.Well,thats my explanation for them.
A huge population of unbound planetary-mass objects was predicted in the Astrophysical Journal in 1987 [vol. 322(1), pgs. 34-36]. Pulsar-planets were also later predicted in a published paper.
Reply | Report Abuse | Link to thisA discussion of this form of dark matter and its detection via microlensing was published in:
http://arxiv.org/ftp/astro-ph/papers/0002/0002363.pdf
It is a great pleasure to see this population finally being revealed to us. The stellar-mass MACHOs and the planetary-mass unbound objects discovered via microlensing may constitute the galactic dark matter, and its specific two-peak mass spectrum was predicted almost 25 years ago. It has been a long wait, but better late than never.
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity; Fractal Cosmology
Jupiter, for example, is <1/1000 as massive as the Sun, so an exceeding large number of even more massive gas giants would be necessary to provide the additional mass prescribed by dark matter hypotheses. IMO, there's an easier way to eliminate the perceived requirement for dark matter: just recognize that billions of stars configured in a vast distribution spanning 100s of thousands of light years should not be expected to rotate like the few planets orbiting the exceedingly massive Sun.
Reply | Report Abuse | Link to thisAlso, I didn't see any mention of these planets being located far beyond the periphery of the galactic disc as is prescribed for hypothesized dark matter. The extended distribution of galactic mass is thought to be necessary to produce the observed galactic rotational curve. Simply increasing mass among the stars and gas of the galactic disc would not produce those observed rotational curves using the applied standard methods of gravitational evaluation.
These lost planets most likely are the product of a 3-body gravitational interaction that ejected them from their planetary systems while sending the other gas giant into an exceedingly proximal (often retrograde) orbit around its host star.
That process could explain why so many gas giants orbit so near their own stars in exoplanetary systems, along with the fact that their size and proximity make them easy to detect...
Wow. That's quite a leap of faith.
Reply | Report Abuse | Link to thisSince our current or predictable technology we already have could allow humans, at slow speeds, to migrate through the galaxy. A couple or 10 million years, and we'd be all over it.
However, we see no evidence for even ONE let alone what "ought" to be loads of life forms flying around.
My favorite theory is that intelligence (as defined by us) is not selected for in the universe.
Thus, any other "experiments" like ourselves have not succeeded, and, given our current direction/momentum, we may not be around much longer either!
There are "objects" around the universe/s that are stationary, moving with other objects and some are freely moving around. The universe "space" is not empty space but has some sort of floating "air" but not known to us that keeps everything where it is and so called gravity and ether are only human conceptions and theories. There are NO humans anywhere else. There are "living" things in space and on planets or objects we call them. We do not have the technology to assess or give firm confirmation on anything right now. It is like life after death situation is it or isn't it.Human mind is fantastic journey into past,present and future. It has the ability to deduce what it wants to see and make it happen. Unfortunately only humans can so other living things have no say in all this. There is NO Universe as we call it but vast space that we do not even know how that is hanging on or within what!container? Humans will find that there are galaxies and other similar gaseous objects but all within ONE Hugh space and time. No Parallels, No Superior Aliens, NO nothing. Just us and the Space with fantastic objects for us to play with and admire the creation of GOD! Indirectly we may put our genes on a planet and that planet may have life later but we are the first and only creatures sorry!
Reply | Report Abuse | Link to thisWon't they feel silly when they find out it wasn't "planets" bending the light from the stars it was anti-biotic resistant bed bugs walking across the lenses of the telescopes bending the light.
Reply | Report Abuse | Link to thisAt least this should add something to the mass we cannot normally see thereby reducing the amount of unexplained mass being postulated as dark matter.
Reply | Report Abuse | Link to thisWhat I find interesting is that these objects, as well as other things like brown dwarfs, can bridge the gap between our solar system and other stars, perhaps providing refueling and reprovisioning stations on the way to those stars. It may take 100's of thousands of years to reach a star 20 light years away but we could reach one of these freefloating objects in a thousand years or less. And who knows what we may be capable of in the next 500 years.
Is this is the case, would it account for the missing mass and avoid the need to invoke dark matter? Just asking, I have no idea..
Reply | Report Abuse | Link to this"By extrapolation . . "
Reply | Report Abuse | Link to thisTHIS is not science. This is sheer subjective speculation, built on the most minute, infinitesimal observation.
The very 'observation' and 'existence of these planets is a process that is fraught with indirect measurement and assumption.
It is clear from the last couple of years that planets are indeed ubiquitous. This is based on dozens or more sources, and dozens of studies across many sectors of the galaxy.
But 'extrapolating' this current 'observation' process of Orphan Planets is really nothing more than Publicity Seeking Scientific Hype ! The kind of Science that brings the subject into disrepute and creates contempt for it in so many sectors of our society.
It is quite possible, and this is mentioned by the authors of the research, that the observed population of unbound planetary mass objects is the high-mass tail of a much larger population of lower-mass planetary-mass objects.
Reply | Report Abuse | Link to thisThe high-mass objects are easier to detect, and so there is an observational bias to their being observed first.
Stay tuned! Dark matter may have been identified, and it ain't no unicorn particles, which have been No-Shows for 35 years.
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Discrete Scale Relativity; Fractal Cosmology
One more time - those who imagine dark matter explains the observed galactic rotational velocities specify that there is at least 6 times as much 'dark matter' as luminous matter in the Milky Way and that it be located in a peripheral halo surrounding the luminous galaxy.
Reply | Report Abuse | Link to thisFor lost planets to provide the missing galactic mass attributed to dark matter, 1,000 lost planets of Jupiter's mass would have to compensate for every star of the Sun's mass. If the ~200 billion stars in the Milky Way were all of the Sun's mass then >1,000 * 200 billion * 6, or 6 million billion lost planets would be required, plus enough more to compensate for all the gaseous clouds and other non-stellar mass in the galaxy.
I think it'd be very difficult to lose more than 6 million billion planets even if they mostly for some reason enveloped the periphery of the rest of the galaxy.
I propose: "dark planets".
Reply | Report Abuse | Link to thisAs in: planets that do not have a host star to light them up.
JT- Yes, it would be doubtful that there are enough of these planets to account for all the missing matter, but I wonder how much more matter in unknown forms waits to be discovered. There was a recent paper which I cannot locate now, but which postulated large numbers of massive black holes may exist between galaxies and many 'normal' ones inside galaxies. If these do exist, they could also account for a lot of mass. Like I said, What else is out there waiting to be discovered? Dark matter and energy may not be needed in the end.
Reply | Report Abuse | Link to thisEnough of these objects would account for the Universe's missing mass.
Reply | Report Abuse | Link to thisSince these " inferred" objects are errant planets, perhaps "planerrant" would be a suitable name?
Reply | Report Abuse | Link to thisFrom what I understand "Planet" means "wanderer" so "planet" is a better name for that group of objects than it is for our Earth. What is latin for "tethered"? That's what we should call the planets of our system.
Reply | Report Abuse | Link to thisI agree wholeheartedly! The article states:
Reply | Report Abuse | Link to this"By extrapolation, the study's authors, from the Microlensing Observations in Astrophysics (MOA) collaboration and the Optical Gravitational Lensing Experiment (OGLE) collaboration, calculate that there should be almost twice as many such objects in the Milky Way as there are stars."
It goes on to state that "the new discovery came out of a MOA survey of 50 million stars in 2006 and 2007."
I dislike doing math, but I don't understand how a sample of 50 million stars producing 10 qualifying microlensing events can be 'extrapolated' to predict that their are 2 such lost planets per star, or up to 800 billion lost planets in our galaxy! This prediction is truly an extraordinary claim requiring extraordinary proof!
@HowardB, no one claimed that the conclusions here are factual. They made it quite clear how they came to their conclusions. The purpose of the conclusions is to form a basis for more research. The predictions made can then be validated against new results. I don't know how you imagine science works but keeping the results of a study secret until one can derive a new theory is not it. Science is about probabilities not absolutes. Sometimes the purpose of research is to help point the direction for new research and not to validate a particular theory. If anything brings science into "disrepute" it is the unjustified expectations of those who don't seem to understand the process. And also those who look for any reason at all to cast a shadow on science to advance an anti-science agenda.
Reply | Report Abuse | Link to thisGreat - one more thing Earth can get hit by...
Reply | Report Abuse | Link to thisWhen is a planet not a planet? In the Star Wars Trilogy there was the creation of the Death Star, a ship the size of a small planet. On the one hand we want to believe that we are the only game in the galaxy and the universe, so we look at the the night sky amazed be the stellar object that surround us. Maybe want we are looking at are not planets at all, but actual starships whose technology is light years ahead of us. Is it better to travel through space than to actually bend space, and if you can bend space how much power would you need to do it. We as humans are in the lower range of technological development and have a long way to go before we are capable of traversing inside our own solar system; let alone outside the protective glow of our own sun. Can we see the galaxy filled with life, or are we just looking for a reflection of our own image? Fact is stranger than fiction.
Reply | Report Abuse | Link to thisIn this scientific observation of 10 Jupiter sized object that have no star attatached, how can they theorize an estimate value of an unknown? How long have these ten objects been observed and are they connected? Out of 50 million stars we find 10 objects that are out of the planetary norm. Maybe they should study these ten objects and understand what makes them what they are, instead of making galaxies out of solar systems.
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisI realize that it would involve some serious effort on your part, but you might try reading the paper.
Here it is:
http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.3544v1.pdf
The extrapolation is from lensing probabilities. The free floating planet needs to be precisely located between a star and Earth. It appears this has a probability of one in ten million. Think of it as the proportion of the sky taken up by the area the 50 million stars.
Reply | Report Abuse | Link to thisThe survey appears to have been conducted over a period of two years, focusing on star forming regions. During any star observation period, the probability that an isolated planet moves precisely between the observed star and the the observer must depend not only on the number of isolated planets but their relative motions and the duration of observations. IMO, simplistic estimation of event probabilities is suspect, but I don't like math.
Reply | Report Abuse | Link to thisFor all those who would hope this discovery, even if does represent 2 unbound planets of 3-15 Jupiter masses (1/1000 of the Sun's mass) would account for any significant portion of the perceived 'missing mass' considered to be provided by hypothesized dark matter, consider that:
Reply | Report Abuse | Link to this- To produce the observed rotational velocity curve using standard methods of galactic gravitational evaluation, it is currently thought that almost all dark matter must be contained within a distant peripheral halo, not anywhere within the visible galactic disk. In fact, increasing the estimated mass configured within the galactic disk would proportionally increase the amount of estimated dark matter required to be configured within the peripheral halo.
- It is currently estimated that the amount of mass provided by dark matter configured within the peripheral dark matter halo (located between 100,000 and 300,000 light years from the galactic center) is about 10 times the mass provided by ordinary galactic matter.
ref. Battaglia et al. (2005), "The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way", http://www.arxiv.org/abs/astro-ph/0506102
Pardon me for a "dark" pun. As a literal "stab in the dark".
Reply | Report Abuse | Link to thisDoes anyone know if someone has entertained an idea that the masses of all these uncounted billions of misterious dark Jupiter size (hopefully Jupiter mass) objects apparently lost in the cold, dark wastness of the glaxy (and beyond) could somhow add up to account for the gravitational effect equal to the one currently attributed to the equally misterious and evasive dark matter?
I will be very grateful if some one, hopefully more enlightened then me, could shed some light and hopefully debunk, this "stab in the dark" conjecture.
Are you kidding? Why would anyone respond to your question, since you haven't even bothered to read the comment preceding yours, much less all the others?
Reply | Report Abuse | Link to thisIf the sun is merely a gas giant with a fusion reaction, could we eventually find a massive star with many much smaller stars (like ours) in orbit around it? Not binary, more an actual solar system?
Reply | Report Abuse | Link to this"I don't know how you imagine science works" "If anything brings science into "disrepute" it is the unjustified expectations of those who don't seem to understand the process."
Reply | Report Abuse | Link to thisWell having spent 30 years in science I suggest I know more about what Science means and how it works that most people and you patronising comments achieve nothing except make you look silly.
"They made it quite clear how they came to their conclusions. The purpose of the conclusions is to form a basis for more research."
This is not quality Science. Coming to 'conclusions' based on such infinitesimal observations and making 'claims' like this is the stuff of tabloid Science. If they were interested in quality Science they would have reported their findings while clearly stating the limitations of their scope. They would have been far more cautionary in their willingness to then claim such a remarkable conclusion if their results were extrapolated across the universe.
Poor science. Clearly aimed at grant money and publicity.
VERy well said kristi276.
Reply | Report Abuse | Link to thisWith respect jtdwyer - I would suggest that that was a wholly undeserved response considering the whole subject of Dark Matter is shrouded in uncertainty and many many competing theories. A question from someone who may simply be taking an interest in an interesting part of Science should be encouraged, however silly 'You' may opine it to be. Ease up ?
Reply | Report Abuse | Link to thisI made no remark about the question being silly - only that the questioner should have first read others' questions and comments.
Reply | Report Abuse | Link to thisIf the questioner should have at least read the comment immediately preceding his/her own he/she would have at least found that it's not such a silly question (as he/she seemed to fear) but one that many others share. Any answers to the question would have to be received by reading others' comments - why not read others' prior questions and comments - not interested enough to put forth the effort required?
Could these non-orbiting planetary masses account for the descrepancies in measuring galactic mass? In other words, can these blobs of mass be the explanation for "dark matter"?
Reply | Report Abuse | Link to thisThis discovery does not meet the requirements for galactic dark matter: the missing mass must be configured outside the periphery of the visible galactic matter in order to produce the observed flat or increasing rotational velocities as a function of distance from the galactic center using the evaluation methods employed by astronomers to infer the existence of galactic dark matter.
Reply | Report Abuse | Link to thisIt is currently estimated that the amount of mass provided by dark matter configured within the peripheral dark matter halo of the Milky Way (located between 100,000 and 300,000 light years from the galactic center) is about 10 times the mass provided by ordinary galactic matter. ref.: Battaglia et al. (2005), "The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way", http://www.arxiv.org/abs/astro-ph/0506102
The few planets in the Solar system, in effect, each independently orbit the dominating mass of the Sun, which contains 99.86% of total system mass. The laws of planetary motion empirically derived from observations of the motions of planets in our Solar system describe the specific motions produced by this specific configuration of mass, with a few orbital bodies independently rotating around a dominatingly massive object.
While the planar configuration of spiral galaxies may be reminiscent of planetary orbital systems, they do not share their critically specific central concentration of system mass. Astronomers should never have presumed that Kepler’s ‘laws’ of planetary motion automagically applied to galaxies as well. Since they do not, there is no need for compensatory galactic dark matter.
jtdwyer,
Reply | Report Abuse | Link to thisPlease read the article before criticizing their research based on your assumption that they used a "simplistic estimation of event probabilities."
http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.3544v1.pdf
The survey was not "focusing on star forming regions." The survey was on the galactic bulge.
I stated a very simplistic conceptual method of determining the probabilities so that you could understand the numbers (10 events per 50 million observations). I didn't believe you would take it literally ("think of it as..."). In reality it is a complex mass function modeling the galactic bulge that does include velocities. Using Monte Carlo analysis the number of events are then be predicted.
I'm sure you're probably right, but I did scan the research report. In my simple mind I understood that the telescopes were focused on stars in the galactic bulge, but the the planets producing the microlensing events were located in star forming regions. As I understand, it is the planets' eclipsing motions relative to the stars in the galactic bulge and the duration and frequency of observations that determine the probability of detecting microlensing events. But I probably just don't understand.
Reply | Report Abuse | Link to thisIn any event, anyone who claims to have determined that a population of hundreds of billions unattached planets exists in the Milk Way should be required to provide not just an extrapolation of 10 detection events to infer the presence of such a large population but extraordinary evidence, as this is an extraordinary claim.
The purpose of publishing scientific research results is to make them available for critical assessment. If this research cannot withstand my comments it certainly should not be accepted by anyone.
jtdwyer,
Reply | Report Abuse | Link to thisI did not see anything that suggested that the planets (i.e. lensing objects) were in star forming regions. Could you please reference page and paragraph if you read this.
The statistics used in the paper is reasonably robust. Even Joachim Wambsganss, who wrote the commentary, said that the evidence is "pretty convincing." He has significant expertise in gravitational lensing and extrasolar planets. Do you?
I do not have this expertise and I would not consider myself one of peers in the peer review process, especially after only a "scan of the research report." As Takahiro Sumi said, WFIRST should be used to find more objects. Further research is needed. The case is not closed; and nobody claimed it to be.
Dear, Jtdwyer. As silly as my question might sound, I did bother to read the prior comments. Particularly I did read the article of Battaglia et.al. And I do understand that many scientists had a fair amount of scientific "stabbing in the dark" by hanging their hats (and their scientific careers) on the "dark matter" hypothesis. However, this article (at least to me) appeared to be somewhat different. For the first time to my (rather limited) knowledge the authors aquired what appears to be hard (albeit, indirect) evidence of dark (otherwise unobservable and undetectable) gravitational bodies existence. With all due respect and apologies, a fair qustion to ask is this. If enough of such dark bodies do exist, wherever they need to to exist (be that the galactic centre or galalctic gulag) to hold the galaxy together abiding only Newtonian gravitational forces (without resorting to Dark Matter). Can the "swarms" of these dark bodies be somehow detected (or otherwise) using current technology to confirm or deny the plausibility of their existence?
Reply | Report Abuse | Link to thisApparently you missed the statement on page 1 of the report you reference, "There is some evidence of free-floating planetary mass objects in young star-forming regions, but these objects are limited to massive objects of 3 to 15 Jupiter masses with large uncertainties in photometric mass estimates and their abundance." I must admit that I misremembered the statement as applying to the planets discovered by microlensing - as I previously stated I had only scanned the report.
Reply | Report Abuse | Link to thisPerhaps my skepticism of extraordinary claims is a result of the dark matter debacle. Vera Rubin worked for more than 10 years to convince astronomers that observations of spiral galaxy rotation curves did not diminish with distance as specified by the 'laws' of planetary motion. Since the laws of planetary motion were the time proven standard method of evaluating the effects of gravitation in orbital systems, once enough observational evidence had been accumulated it was considered conclusive evidence that most of galactic mass was undetected or the effects of gravitation were scalar. Unfortunately, no one questioned the applicability of Kepler's equations as had Newton in his 'Principia'. The extraordinary claim of dark matter has been mostly unquestioned but unsubstantiated for more than 30 years now. Once such an extraordinary claim has become established, it is exceedingly difficult to overturn.
The research report does state: "The duration of the magnification is parameterized by the Einstein radius crossing time, tE ∼ [the square root of] M/MJ days, where MJ = 9.5×10−4M⊙ is Jupiters mass. Thus, microlensing can detect faint planetary mass objects —which are either unbound to any host star or are in very wide orbits — as short-timescale events with tE < 2 days. Although tE also depends on the distance and transverse velocity of the lens (see Supplementary Information), the observed tE distribution can be used as a statistical probe of the mass function of the lens objects because the spatial and velocity distributions in the Galactic disk and bulge are reasonably well known."
I understand that statement to indicate that the background magnified star was located in the galactic bulge and the lensing object was located within the galactic disk (which does happen to contain many active star forming regions where the detected planets could have been formed). These planets must have been formed somewhere – most stars systems are formed in star forming regions…
(continued)
It seems to me that employing a mass function derived for stars for objects that are most likely a secondary product of the stellar production process should be questioned.
Reply | Report Abuse | Link to thisPlease reference the section, ‘8 Relative Frequencies of Unbound/Distant and Bound Planets’ for the conclusion of the estimation of the number of unbound planets:
“…Of course, there are likely to be some planets even closer to their host stars that are undetectable (by microlensing) because of the presence of the host star, so it is reasonable to presume that there are 5 planetary mass objects in binary lens systems in this sample that were detected with approximately the same efficiency as the planetary mass objects detected as isolated lens systems. This allows us to estimate the ratio of the new population of unbound or distant planetary mass objects to the planets found with host stars. The power-law mass function implies 11 isolated planetary mass lenses (that comprise our unbound or distant planetary mass sample) in our full event sample, so this ratio is 11/5 = 2.2.”
I’m neither a physicist not a mathematician, but in my opinion extraordinarily broad assumptions are being made in the researchers’ analyses leading to the estimation of an extraordinary number of unbound planets in our galaxy. Moreover, I agree that the evidence for the 10 detected unbound planets is “pretty convincing”, but I strongly suggest that the evidence for billions of these objects is exceedingly weak.
Please everyone, desist with the 'silly' references, since I never characterized anyone's comments as 'silly'.
Reply | Report Abuse | Link to thisDarth Evader (if that is your real name) - please go back and read your original comment and my preceding comment. If you had read my comment (posted nearly 2 hours prior to yours), why did you ask whether this discovery could "account for the gravitational effect... attributed to... dark matter?"
I had attempted directly address that question in the comment immediately preceding yours. I apologize if I answered out of frustration, since I'd apparently been wasting my time.
I agree that these observations are different than those attributed to dark matter. While the existence of the 10 unbound planets has only been inferred by gravitational effects, there is no assertion that they cannot be directed detected. That does leave open to possibility that they could be directly detected by EM emissions. I would hope that astronomers could confirm the existence these or other unbound planets through some more direct method of detection.
As for confirmation of the estimation of billions of unbound planets, astronomers have a lot of observing to do, IMO.
IMO, there is no need for additional mass, dark or otherwise, to explain why the rotational velocities of galactic masses do not generally diminish as a function of distance from the galactic center - vast distributions of masses locally self-gravitate (in accordance with inverse-square law) rather than only being attracted to a center of mass many thousands of light years away.
As the Battaglia et al paper explained, unlike disc masses, the rotational velocities of discrete objects of mass (old stars, globular clusters and satellite galaxies) orbiting the periphery of the galactic disc ARE diminished. Self-gravitating discs and other relatively dense large scale distributions of mass do not qualify as planets and cannot be expected to behave as such.
Based on the methods used to evaluate gravitational effects within galaxy clusters, the discovery of additional mass not presently included in astronomers' mass/light based method of galactic mass estimation might help 'shed some light' on their inadequate methods.
JTDwyer,
Reply | Report Abuse | Link to thisI read the statement on page 1. Those "free-floating planetary mass objects" are NOT the 10 Jupiter-size objects analyzed by MAO in this paper.
Star forming regions are typically populated by young stellar objects. The Milky Way is over 13 billion years old. Most of the stars and planets in our galaxy were formed billions of years ago. Our galaxy produces approximately one solar mass of stars per year. Again, the paper said nothing about the 10 Jupiter-size objects being in star forming regions.
You said, "It seems to me that employing a mass function derived for stars for objects that are most likely a secondary product of the stellar production process should be questioned."
I believe you have misunderstood and over-simplified the model simulations they used.
I believe you have misunderstood the conclusions of section 8. They were comparing the frequencies of unbound/distant and bound planets. They were NOT estimating the number of unbound planets. They do this to compare their results with other estimates.
They then go on to say that it is possible that over half of their 10 lensing events are distant bounded planets (> 7-45AU).
I'll go with Joachim Wambsganss on this.
By the way, JT: Saturn, Uranus, and Neptune would qualify for the 10 lensing objects analyzed by MAO and OGLE. They are approximately 10AU or more from the host star. Most of the 500 exoplanets found so far have been in much tighter orbits.
Reply | Report Abuse | Link to thisGive me a break, Cramer! I already told you that I had misremembered the statement on page one - now you again shout that out to me! Are you asserting that these or any other planetary masses form in NON-star-forming regions??? I would have to argue that point with you, but it was never really important in this discussion!
Reply | Report Abuse | Link to thisThe introduction states:
"These planetary-mass objects have no host stars that can be detected within about ten astronomical units by gravitational microlensing. However a comparison with constraints from direct imaging suggests that most of these planetary-mass objects are not bound to any host star."
Section 8 states:
"Since the new unbound or distant planetary mass population is comprised of ∼ 1.8 times as many Jupiter-mass planets as stars, this comparison with the direct detection limits suggests that at least 75% of these unbound or distant planetary mass objects are not bound to any host star."
I take Section 8 to be the final detailed analysis the study is based - it is continuously referred to in the main article. This seems to be confirmed in the introduction with the summation:
"Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice (1.8 +1.7/−0.8) as common as main-sequence stars..."
I stand by my assertion that the extension of this small sample to the entire population of galactic stars that is questionable. It is this that produced the extraordinary claim that their are nearly two unbound planets for each of the 200-400 billion stars in the galaxy.
If you can, please explain in straightforward terms how it was determined that their are two unbound planets per star in the Milky Way. Otherwise, I will remain unconvinced!
By the way, this (SA) article quotes astronomer Mark McCaughrean of the ESA: "This is a pretty remarkable claim."
It goes on to state:
"...it will no doubt undergo close scrutiny. But if the interpretation proves correct, a future NASA mission could turn up such free-floating bodies in droves. A planned spaceborne observatory called the Wide-Field Infrared Survey Telescope (WFIRST) should be able to discover 1,000 such objects, says study co-author Takahiro Sumi of Osaka University in Japan, a member the MOA group."
This study has not presented definitive evidence that there are hundreds of billions of unbound Jupiter mass planets in the galaxy as it asserts. If their complex extrapolations are correct, then WFIRST should confirm their predicted enormous population of unbound planets.
JT,
Reply | Report Abuse | Link to thisWho was claiming that this research offered "definitive evidence that there are hundreds of billions of unbound Jupiter mass planets in the galaxy???" That's a long way from you first saying that "simplistic estimation of event probabilities is suspect." You first basically said their research was bogus; and now I guess you're saying that it is not definitive evidence. Yes, I agree, it is not definitive evidence.
You still seem not to understand where the 1.8^+1.7_-0.8 comes from. It does NOT come from Section 8. I can't "explain in straightforward terms how it was determined that their are two unbound planets per star." First, there wasn't two unbound planets per star. The 1.8 includes >10AU bounded planets (orbit of Saturn). It's more like 0.75 to 1.25 unbound planets per main sequence star.
You can study up on it. To start, maybe you can look at these papers:
http://arxiv.org/PS_cache/astro-ph/pdf/0002/0002510v2.pdf
http://arxiv.org/PS_cache/astro-ph/pdf/0003/0003392v1.pdf
http://www.jstor.org/stable/pdfplus/10.1086/376392.pdf?acceptTC=true
Give you a break???
You are the one who said I "missed the statement on page 1." You then went on to defend that these planets as coming from star forming regions: "These planets must have been formed somewhere." I found your statements contradictory.
I am NOT claiming that I know where the planets are located. Some might actually be in the bulge itself. Considering how much chaos there is closer to and inside the bulge, it doesn't surprise me that planets can be thrown out of orbit over billions of years. Stars are even flung out of the galaxy.
I have no reason to believe that their research (from two independent teams) is "SUSPECT." That sounds like intellectual masterbation for a person with no expertise in a field to criticize research results from that field that are based on statistical and mathematical methods that are not understood by that person. Intuition can not substitute for science; and I believe you are expert enough in your own field to understand that.
You can read part of the commentary from Joachim Wambsganss here:
http://www.planta.cn/forum/files_planta/species_loss_revisited_201.pdf
(it starts on the 2nd page)
So you dispute the researchers introductory statement that I quoted in my preceding comment, that:
Reply | Report Abuse | Link to this"However a comparison with constraints from direct imaging suggests that most of these planetary-mass objects are not bound to any host star?"
You stated:
"I am NOT claiming that I know where the planets are located. Some might actually be in the bulge itself."
You may not realize it, but that statement reveals complete ignorance of microlensing. I can state with great certainty that NONE of the detected lensing planets could POSSIBLY have been located within the Galactic bulge! You are in dire need of basic education in the microlensing phenomena.
Of the 10 identified lensing masses, it is most likely that they are located about halfway between the lensed objects and the observer.
Again, the introduction states:
"...two years of gravitational microlensing survey observations toward the Galactic Bulge."
In these unfortunate discussions, I mistakingly adopted your earlier assertion that the lensed stars were located in the galactic bulge. Observations were directed towards the bulge to maximize the stellar density of the field of view, but could have been located almost anywhere from the bulge to the Milky Way. If you look, you'll find that the Supplementary Information discuses lensed objects found in both the bulge and the disk.
By the way, if I'd intended to use the words 'bogus' or 'silly' I would have done so. Since you continue to bicker about things you don't at all understand, put derisive words in my mouth and personally insult me, you'll be pleased that I will not respond to your obsessively abusive remarks in the future.
JT, we seem to be having some communication problems. For my part in that, I apologize.
Reply | Report Abuse | Link to thisI have NOT disputed anything in the joint MOA-OGLE research paper. The lens objects have no host stars "that can be detected." That does not mean there are no host stars. That's why they named the paper "Unbound or Distant Planetary Mass Population..." As you later quoted, "75% of these unbound or distant planetary mass objects are not bound to any host star." If you read the paragraph that follows that quote on page 25, you would see that they also said it was possible that the majority of lens objects can be bound to host stars. Half of 1.8 is 0.9.
I repeat: some of the lens objects could ACTUALLY be in the bulge itself. That statement was meant to imply a small probability. They are most likely all in the disc. How can you state "with great certainty that NONE of the detected lensing planets could POSSIBLY have been located within the Galactic bulge!"??? Do you have a list of their locations??? There are only ten of them. Produce the list.
I believe you are not correct regarding the location of the source stars (lensed stars, as you called them). Here is a statement by Sumi: "In a typical scenario, the source belongs to the Galactic bulge, while the lens can be part either of the bulge (2/3 of the events) or the disk (1/3 of the events) population."
Source: Microlensing search for extrasolar planets
http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU3_S249%2FS1743921308016323a.pdf&code=4e45555e8529fa43559d97c60a9e146d
This entire dialogue escalated because of the one comment you made: "IMO, simplistic estimation of event probabilities is SUSPECT, but I don't like math." You can try to sugarcoat that statement all you want, but my interpretation is that is the same thing as saying that their research is either bogus or fraudulent. The "derisive word" is SUSPECT. That means "fishy, shady, questionable motives." You are actually accusing them of fraud. Bogus is actually a less derisive word that does not necessitate intent. Maybe you should reconsider who has been doing most of the insulting.
Correction: The link that I provided was dynamic and does not work.
Reply | Report Abuse | Link to thisHere's another link that will work:
http://arxiv.org/PS_cache/arxiv/pdf/0711/0711.4750v1.pdf
Microlensing search for extrasolar planets: observational strategy, discoveries and implications
Arnaud Cassan, Takahiro Sumi, Daniel Kubas
Proceedings IAU Symposium No. 249, 2007
To see all the papers from that symposium:
http://journals.cambridge.org/action/displayIssue?decade=2000&jid=IAU&volumeId=3&issueId=S249&iid=1864004
I fully anticipate that we or our descendants will have to revisit the definition of LIFE itself again, now that we have discovered these free floating planets, which must pass through a greater range of conditions than obtains on Earth. There is absolutely no reason why the information contained in the polymers that give us our earthly DNA could not develop in the same complexity and structures dictated by the physics of fractals but using totally different chemical combinations. (Star Trek, here we come. I've seen so much former sci fi come to reality in my life time that I've come to the belief that we are incapable of conceiving of anything that is not somehow possible, sooner or later. Now I'll spoil it, for most of you, by saying, even heaven!)
Reply | Report Abuse | Link to thisFrish, you are still thinking humanoids, for intelligence, including DNA and biology. I agree that it is unlikely that we will find life forms like ours in the universe in the next billion years. However look at the computer that we are using right now. The universe has evolved us, a million times more complex than any computer, so why could it not evolve a silicon life form or germanium or some other chemical polymer sufficiently complex as to store and replicate the information that is necessary for reproduction. Once that has happened, as we have seen here on earth, it is only a matter of time before the LAWS of evolution take them into the realm of intelligence. The differences in scale and chemical composition might make it difficult for such life forms to perceive or find us interesting, and vice versa, but I have a strong suspicion that they do exist.
Reply | Report Abuse | Link to thisJT, I tire of your tirade, how you profess ignorance of astronomy and mathematics yet proclaim your theories regarding such, showing much disdain to any that have thoughts otherwise. One question, what do you meant when you say "Observations were directed towards the bulge to maximize the stellar density of the field of view, but could have been located almost anywhere from the bulge to the Milky Way"? Is not the bulge in question the bulge of the Milky Way galaxy itself? And if so, how could something be located between the Milky Way galactic bulge and the Milky Way. I know it is nit picking, but you are a bit of a nit
Reply | Report Abuse | Link to thisA Maverick moon would be a good place to set up shop if you intended to travel extrasolar.. the gravitational stresses would generate enough heat to support life, like Io, Titan, and Enceladus. (heat)
Reply | Report Abuse | Link to thisOne could easily calculate the required mass and orbital momentum required to draw this amount of energy from the system for the duration of an interstellar transit.
I do believe that "planet" means "traveler" or "wanderer". I see no problem in applying this name to the real travellers of the Galaxy.
Reply | Report Abuse | Link to thisJT Dwyer's statement preceding your "nit picking" quote was:
Reply | Report Abuse | Link to this"In these unfortunate discussions, I mistakingly adopted your earlier assertion that the lensed stars were located in the galactic bulge."
I find it amazing that he believes that "lensed stars" are not in the bulge. I wonder where he believes the galaxies shown in the Hubble Deep Field images are located? Is he not aware that they purposely select fields that are absent of foreground stars located in the Milky Way disc?
I will repeat the quote from the first paragraph of the following research paper:
http://arxiv.org/PS_cache/arxiv/pdf/0711/0711.4750v1.pdf
"In a typical scenario, the source belongs to the Galactic bulge, while the lens can be part either of the bulge (2/3 of the events) or the disk (1/3 of the events) population."
JT Dwyer has still not produce the locations of the lens objects and source stars for the 10 events analyzed in the paper (MOA-ip-1 to ip-10).
JT Dwyer is nowhere to be found. I hope he has realized his errors. I am here to learn new things. I don't know if all commenters have that same objective.
I wonder if anybody will ever consider what seems to me a very likely possibility that the "missing mass" in the universe isn't missing at all. There is no goofy dark matter, either. There are just billions upon billions of failed stars, planets and asteroids out there that collectively add up to much, much more than what we have been able to detect so far, and in some parts of the universe they may be especially dense.
Reply | Report Abuse | Link to thisI predict that in the next several years we will be discovering more and more of these and some crackerjack PhD student or associate professor will sneak a paper into a journal somewhere that will make the case for what should have been considering all the time. He will be called a dark matter "denialist" at first, but gradually it will take hold as the dark matter guys die off. Finally, it will win acceptance.
The flaw with the dark matter hypothesis is that it was an explanation invented to explain something that was not yet apparent. After all, there must be "something" out there and we can't see it, right? It must be matter and it sure is dark.
Me, what do I know? I'm just a retired carpenter who reads science magazines.
Laird,
Reply | Report Abuse | Link to thisThat would be a great opening to a lesson on the fallacy of false equivalence.
It could also be the opening of a lesson in the denial of uncertainty.
Yes, there is uncertainty in our world. I try never to fall into the trap of creating a straw man of a scientist's beliefs (or anybody for that matter). Most scientists understand the uncertainties of the theories they are researching. That is the entire basis of their profession. However, scientists are also human. If someone has dedicated their life to working on a particular theory, they are likely to have a problem letting go if that theory fails, especially when their career, reputation, and livelihood are dependant on it. That only has to do with a swing of the pendulum of uncertainty from a significant likelihood of the theory being true to it being untrue. This happens in all science, but more so in the "soft" sciences such as economics.
When someone has little or no expertise in a particular science, they can fall into the trap of false equivocation of theories due to their ignorance of uncertainty levels. Should it be a requirement that a member from the Flat Earth Society sit on a budget committee for NASA? Are all scientist working at the Large Hadron Collider extremists?
The best way to get a better grasp on the uncertainties in our world is to educate oneself. From your statements it is apparent that you do not understand what astrophysicists know and don't know, as well as the degree of uncertainty they recognize in their theories. Scientists that do not believe dark matter exists are not considered extremists. So your prediction of some Galilean scientist being ostracized as a dark matter denialist is meaningless.
Reply | Report Abuse | Link to thisThese planets cannot replace the perceived requirement for dark matter, since its specified to provide more than 6 times the mass of ordinary galactic matter and be located beyond the detectable galactic periphery.
However, I agree with your other points.
I have no education or background in physics - I'm just a retired information systems analyst with >30 years experience. In 2008 I heard Vera Rubin explain the 'discovery' of inferred dark matter in the BBC documentary "Most of Our Universe is Missing" (transcribed):
"If we observe the velocities of stars orbiting in the galaxy we find that their velocities remain flat all the way to the edge of our observations - that's not what was expected. By correspondence with the Solar system and in fact just from Newton's law it was expected that the velocities of the stars would fall off. So it was clear that our ideas about galaxies were incorrect."
Knowing only that gravitation's effects were proportional to mass and diminished with distance, I could not understand how the centralized mass Solar system and the exceedingly distributed mass of, especially, spiral galaxies could possibly be expected to rotate identically. It seemed to me that there must be some fundamental misconception involved in this galaxy rotation problem.
I'd never studied physics - it was instead my extensive experience debugging very difficult problems in extremely complex, large scale, critical information systems that I hoped to bring to bear on this problem. I naively thought I could just inform someone of this error and be done with it. I started with Vera Rubin, but never received a response, so I had to continue my investigation. I did write an essay last year, which can be found at: http://www.sciencewithoutfiction.com/uploads/Mass_Distribution-_Galaxy_Rotation_Problem.pdf
In a nutshell, the perceived requirement for dark matter became established because it was expected that the rotational velocities of stars in the discs of spiral galaxies should diminish with their distance from the galactic center, in compliance with the laws of planetary motion. As Newton described in his "Principia", Kepler's laws presume relatively sparse, low mass objects orbiting a dominating central mass (the Sun contains 99.86% of total Solar system mass) such that they do not significantly perturb one another: they in effect independently orbit a central mass. This does not describe the mass configuration or gravitational effects of vast distributions of massive objects known as galaxies.
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Reply | Report Abuse | Link to thisAlong the way I have discovered some others who had independently come to essentially the same conclusion and could more completely describe the problem in the terms of physicists.
Right about 2000 a retired aeronautical engineer produced a series of unpublished papers identifying errors in the original gravitational analyses that established the general acceptance of the galaxy rotation problem in the 1970s. He also developed more appropriate methods of galactic evaluation. These papers received little attention for several years. These works can all be found in the references of: http://arxiv.org/abs/astro-ph/0309762 and
http://arxiv.org/abs/0806.1131
In 2005 a physics professor submitted a research report to the Astrophysical Journal, "General Relativity Resolves Galactic Rotation Without Exotic Dark Matter",
http://arxiv.org/abs/astro-ph/0507619
That never published paper with the tantalizing title quickly became the subject, or target, of several science blogs and articles. Several research papers were written specifically to criticize, in different ways, the methods employed to represent galactic discs:
[valid links to 6 papers deleted per SA's spam checker]
Eventually one independent research paper was written supporting the original methods:
http://arxiv.org/abs/0807.1132
After five years, as second paper was written late last year with an apparently less inflammatory title: "General relativistic dynamics applied to the rotation curves of galaxies", http://arxiv.org/abs/1101.3224
I haven't reviewed these comments with anyone involved: they represent only my investigation and conclusions. IMO, There are a large amount of research funding that has been granted to the study of 'dark matter' of the past 40 years. Careers and professional reputations have been made on the basis of that research. Anyone who seriously questions the validity of the initial findings indicating the inferred existence of dark matter is bound to meet with some professional resistance.
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Reply | Report Abuse | Link to thisMore recently, the earlier work of Kenneth Nicholson has been extended by physicists working in an unrelated field (materials research):
http://www.arxiv.org/abs/1007.3778
A specific case using independently developed methods has been published:
http://www.iopscience.iop.org/0004-637X/679/1/373/
These studies indicate that dark matter is not necessary to hold galaxies together: the gravitational effects of distributed masses is sufficient.
Employing galactic disc objects as microlenses have been used to test for the local presence of a dark matter halo:
http://www.arxiv.org/abs/1103.5056
A study of hundreds of discrete Milky Way (ordinary matter) halo objects, including satellite galaxies, globular clusters, and old stars are used to constrain the mass and distribution of a dark matter halo:
http://www.adsabs.harvard.edu/abs/2005MNRAS.364..433B
More interestingly to me, unlike the (self-gravitating) galactic disc, these more distant discrete objects do generally comply with the Keplerian rotational curve! From that direct evidence I infer that it is the independent orbits of discrete objects around a dominating mass that produces orbital velocities diminishing with distance. Distributed mass galaxies should not be required to rotate like sparse planetary systems.
IMO, unrelated professional experience and common sense can often provide insights necessary to solve the most difficult problems of subject area experts. Even brilliant scientists are not always perfect...
James,
Reply | Report Abuse | Link to thisIf such a planet ["-sized body"] traversed the solar system it would be truly alarming. Hopefully it would be so fast that it doesn't upset the orbits of the major planets. Judging from the apparently long stability of the Earths orbit [evolution of life = 90% of Earth's existance] it seems that there must be some mechanism in the galaxy that prevents wayward "planet-sized objects" [for want of a better word] from entering the solar system or, indeed, our area of the Milky Way galaxy.
The IAU has fumbled in their haste to be THE authority:
Reply | Report Abuse | Link to thisI believe we better go back to defining a planet simply by its size. Perhaps, spherical but not glowing in IR or visible. When necessary add the adjective/modifier. Then it becomes necessary for IAU to make a list of acceptable modifiers. No modifier assumes the traditional 9 solar planets. Perhaps "bound planets", "free planets", and some word to discriminate between planets that have cleared their orbital space 360, and those which have not [Ex: Pluto and the Kuiper-belt objects]. This brings up the question of how to categorize Neptune because Pluto does cross it's orbit, but I believe [tell me if I'm wrong] there's a harmonic between their periods that precludes further gravitational interaction.
"Minor Planet" works for the large asteroids, it is debatable if that works for Pluto.
"Are we alone" refers to either extra-terrestrial life or intelligent extra-terrestrial life, not simply to other planets. Certainly there's "hope" to find simple life on some small percentage of exoplanets bound to a stable single star, but how could some free-floating planet possibly harbor life without a nearby heat source?
Reply | Report Abuse | Link to thisThe sun can't attract a maverick into orbit. It can attract it, then it can swallow it, cause a collision with a solar planet, change its [hyperbolic] orbit but it can't bring it into any orbit similar to the known solar planets.
Reply | Report Abuse | Link to thisIt can blow through, but not capture.
Actually we are trapped in a gravity orbit around our sun. And we aren't alone in intelligence either. Intelligence is local and if we are by definition 'smart' a whole lot of ignored intelligence exists right here.
Reply | Report Abuse | Link to thisSo the suns are a whole lot lighter and Miles Mathis has refigured the weight of the sun, and the bodies that would orbit it are lighter also needing very light gas to support themselves, and the plus is that everything about themselves and their planets and their sun are ephemeral. Freed from the terror of gravity they would exist outside our vision and detection. Imagine how many varying gas pressure fields there are out there. Uncountable. Innumberable. Could we ever go there? Could we go to a cloud?