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Most Planets In the Universe Are Homeless
StartsWithABang writes: We like to think of our Solar System as typical: a central star with a number of planets — some gas giants and some rocky worlds — in orbit around it. Yes, there's some variety, with binary or trinary star systems and huge variance in the masses of the central star being common ones, but from a planetary point of view, our Solar System is a rarity. Even though there are hundreds of billions of stars in our galaxy for planets to orbit, there are most likely around a quadrillion planets in our galaxy, total, with only a few trillion of them orbiting stars at most. Now that we've finally detected the first of these, we have an excellent idea that this picture is the correct one: most planets in the Universe are homeless. Now, thank your lucky star!"
don't planets need some kind of gravity source to pull all the dust and shit together?
so much resources out there for the taking, no need to come to earth
This impacts Drake equation and might shed light as to why we have not detected any other sentient life in the universe.
>> most planets in the Universe are homeless
I wonder if they also smell like urine (http://science.slashdot.org/story/14/10/26/1226209/rosetta-probe-reveals-what-a-comet-smells-like).
Planet is Greek for wanderer. So, I think the name is even more appropriate.
Just because most planets belong to a solar system doesn't mean that most solar systems don't have planets. That it is atypical for a planet to orbit a star in no way indicates that it is atypical for a star to have orbiting planets.
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I always wondered why wandering planets couldn't be used instead of dark matter to explain where all the missing mass is.
Any body that is sufficiently massive enough to pull itself into a reasonable facimile of a sphere, yet not massive enough to generate energy from fusion, is a planet, whether it orbits a star or not. And there's your missing "dark matter".
Now not only do I have to be thankful that I have a roof over my head, now I have to be thankful I have a star over it to.
you'd think most of them were captured in larger gravity wells rather then wizzing around.
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Any body that is sufficiently massive enough to pull itself into a reasonable facimile of a sphere, yet not massive enough to generate energy from fusion, is a planet, whether it orbits a star or not. And there's your missing "dark matter".
Tell that to Pluto.
Actually these are not planets according to the new classification.
First, it must orbit the Sun.
Second, it must be big enough for gravity to squash it into a round ball.
And third, it must have cleared other objects out of the way in its orbital neighborhood.
http://missionscience.nasa.gov...
The IAU definition only applies to objects in this solar system. It says nothing about objects outside this solar system. It is very clear about that.
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Space 1999 was so prescient!
2) These should be called slacker stars. They had so much potential, but just blew it all and eventually their parent's kicked them out.
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I wonder if the basic formation of a planetary system can occur without the center mass becoming large enough to be a star. Could you have a system of only unlit planets orbiting around each other. If the gas and dust is swirling around and clumping together, it could conceivably do that even though the mass at the center never gets big enough to ignite. Perhaps something about the way the center star is supposed to push the lighter elements out further away would cause something to not work out right, but to me it seems like it should still work in a similar fashion.
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If the theoretical simulations are correct (these would be the theoretical simulations based on a small number of observations and a lot of conjecture about the underlying forces at work), then the vast majority of planets are homeless. But of course, the headline and the summary state it as a fact.
I'm sure those planets would prefer to be thought of as "free".
(FYI)
There are a few reasons astrophysicists know that it is extremely unlikely that dark matter is baryonic. First of all if all the stars in a galaxy shine on an object it heats up, this heat causes the release of radiation, called thermal radiation, and every (baryonic) object above zero kelvin (or -273.14 deg celcius) emits this radiation. However, dark matter does not emit any radiation at all (hence the name dark!)
If dark matter were baryonic it would also mean that it could become light emitting. If we got a clump of baryonic matter* and put it in space it would gravitationally contract, and would eventually form a star or black hole** - both of which we would be able to see.
So, because of these reasons the dark matter in galaxies and in galaxy groups/clusters cannot be baryonic, and so cannot be planets, dead stars, asteroids, etc. It would definetely not be planets as there is no way 10-100 times the mass of the stars in a galaxy would be planets, as the mechanism for making planets relies on supernovae, and the number of supernovae needed for the that many planets would be far too high to match our observations. I hope that this answered your question!
*provided the clump of baryonic matter was large, and the amount there is in galaxies definitely is!
** we don't observe black holes directly, but can see radiation from their accretion disks.
I will naively assume planets generally form around stars during stellar formation, and don't just spontaneously show up.
So, the homeless planets either spun out during formation ... or ... what, are subsequently ripped away by some other phenomenon? Possibly passing gravity? That about right?
So, if they're hard to see because they don't emit light ... can they possibly be part of the whole dark matter thing? Or is that one different?
If there's quadrillions of planets, and trillions orbiting stars ... there's 3 orders of magnitude more homeless planets than ones in orbits?
The mind truly boggles. Suddenly Space 1999 seems much more plausible to me (I mean the moon flying through space part, not the rest of it).
Lost at C:>. Found at C.
With a few trillion planets in orbit, makes me think that if life is a 1 in a million chance, we've got millions of planets with life just in our galaxy....with at least trillions of planets of life across the universe.
My God can beat up your God. Just kidding...don't take offense. I know there's no God.
I thought orbiting a star was one of the criteria for an object to be called a planet.
summary says there are hundreds of billions of stars, and a million billion (quadrillion) planets, with a thousand billion (trillion) orbiting stars. That's ten thousand planets per star, and 10 orbiting planets per star. Then the conclusion state's most stars don't have planets. I don't follow.
Before one of these hobo-planets comes our way, we should already have a Rotor colony.
You can't handle the truth.
To me there will only ever be one rouge planet. Maybe I'll get to set foot on it.
One day, dear Mars, unless I die first.
"Lack of speed can be overcome. In the worst case by patience." --Znork
Sheesh. So is this the simple explanation to "dark matter" problems in cosmology?
We're out in the backwater. All the action is happening in the core.
Dark matter accounts for something like 90% of the gravitational effects that we see.
I've always suspected that "dark matter" very likely isn't matter at all. I suspect it is simply a gap in our model similar to how relativity filled in gaps for Newtonian mechanics. Dark matter (and dark energy) are basically placeholders for observations that do not match our model. That means one of two things. Either there is something we haven't observed yet OR there is something missing from our model. Both are quite possible but we seem fixated on that former when it could very easily be the later.
I actually do have some background in physics (college minor and worked in some research labs) and I've never have any "real" physicist give me a satisfactory explanation as to why invoking some mysterious matter/energy is a more likely answer than a gap in our models. We understand gravity probably the least of the four forces and we don't have a model that integrates it into our Standard Model. Seems to me that the place to look may very well be in the math rather than in the stars.
We've seen that with Jupiter, if it were not for being in orbit around Sol, Jupiter and its moons would effectively be their own dark solar system.
Systems composed of multiple stars (binaries, etc.) are more common than singular stars, like our Sun. A binary system is a risky place to be -- there is a strong probability that the gravitational interaction between the paired stars would, given enough time, eject any planetary body which forms there -- the "stable" regions depend on the orbital parameters of the two (or more) stars and can be limited to very narrow bands. So, if planetary formation is a typical process around stars and binaries are more common, then it's likely that the galaxy has a large population of planets ejected from unstable orbits around binaries.
For what it's worth, conjecture is that the Sun formed in a cluster and was, itself, ejected. Nearby stars with identical spectra (implying they formed from the same source material) have been identified.
Pretty thin considering the article talks about observed planets exceeded one expected number of planets model and also discusses *other sources* of planets...
The term "solar system" is also used to describe a collection of planets orbiting other stars besides Sol despite the etymology of Solar. Why? Because we have no other term (to my knowledge) to describe a collection of planets orbiting another star....and saying a collection of planets orbiting another star is waaaay too much of a mouthful.
Most really advance races will have probably passed through their singularity – being mechanical-beings they won't really need stars providing warmth to live by. It could be that a huge percentage of these planets are colonized by post-biological-entities and the planets around stars are left as garden areas for new post-biological-entities to emerge from.
Perhaps this is a new direction for SETI
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Oh great. Now we have to worry about killer zombies planets?
It's true, just saw one on the corner. Had a cardboard sign, "Will orbit for $$$".
I eat only the real part of complex carbohydrates.
If you're going to copy an answer from a post on another website, at least give the link:
http://astronomy.stackexchange...
And that answer obviously is wrong. If matter has clumped together into planets, it obviously hasn't clumped together into stars or black holes, and instead has clumped together into objects that are very hard to detect.
Arguments against dark matter being rogue planets are generally based on lack of enough microlensing observations and expected size distributions. But those are far from definitive.
So, the answer is: it is possible that dark matter is all rogue planets, although most physicists believe that it is not.
Because we have no other term (to my knowledge) to describe a collection of planets orbiting another star....and saying a collection of planets orbiting another star is waaaay too much of a mouthful.
And saying "planetary system" is also too difficult?
A planetary system is a set of gravitationally bound non-stellar objects in orbit around a star or star system.
How can they claim that there's more of these homeless planets than not when they've only found one of them...ever!
I understand that we don't have to see something for it to be there but, this leap is just too big to bear.
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Well, in the absence of an explicit definition wouldn't you be presumed to fall back on the default of "things gravitationally bound to the sun"? In fact, in what way could an object not bound to the sun be considered part of the system? Even a rogue planet passing through would only be a temporary anomaly, not an enduring part of the system.
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Maybe. The core's probably a pretty unpleasant place though, with radiation levels so high i's unlikely that life could evolve. Though admittedly by the time a race masters interstellar travel it's probably well on it's way to being able to colonize the galactic core, provided they don't mind living entirely indoors.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Don't mod this guy down. He's at least going by the definition from wikipedia (or a similar reference material), which states:A planet (from Ancient Greek (astr plants), meaning "wandering star") is an astronomical object orbiting a star or stellar remnant that (1) is massive enough to be rounded by its own gravity, (2) is not massive enough to cause thermonuclear fusion, and (3) has cleared its neighbouring region of planetesimals.
I'm sure what this article is calling a Planet meets these 3 criteria but do not meet the "circling a star or stellar remnant" apparent pre-requisite. What I cannot tell you is whether or not Wikipedia is wrong about that "needing to orbit a star" bit - I'm sure someone will respond with a reference defending or refuting that point.
But here’s the funny thing: when we work out the numbers of our best theoretical calculations, the ones produced by getting kicked out of young solar systems represent far less than half of the rogue planets that we expect.
So the author tries to explain a huge number of expected rogue planets, but fails to describe how we've arrived at the number in the first place. "Work out the numbers"? Yes? Could you please share? Why didn't you start with that in the first paragraph?
Also what's with all the exclamation marks? Is this article pitched at grade-schoolers? Fine but if so, what is it doing here?
but we are already using "galaxy" to describe that, which is a pretty cool word.
It may sound cool to us English speakers, but it really just means "milky" in Greek.
What's really annoying is that English punctuation doesn't give any indication that a sentence should be read in an exclamatory or querying tone until you've already finished. It's one of the few things I prefer about Spanish.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
The IAU definition only applies to objects in this solar system. It says nothing about objects outside this solar system. It is very clear about that.
So obviously there are no "planets" at all outside our solar system. ;-)
Maybe astronomers should just make up a new term for the concept. Or maybe several terms. After all, how useful is a term that includes both Mercury and Jupiter? Especially if it excludes Pluto, Titan and Sedna.
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Perhaps that discover will put a stake in that silly redefinition of the word.
And, anyway, this always seemed like the obvious truth. I'd have been shocked if there weren't massive numbers of primary-less planets out there. If you plot star masses versus size, the quantity goes up and up as the mass goes down, to the point they stop radiating. At that point we can't really see them anymore, but there's no reason to doubt that the curve keeps extending.
Some years back (probably in the 1980s), I read an article by an astronomer who had collected lots of info on what was known of the distribution of mass of various sizes. It included a graph of mean size-vs-density, from monatomic H through various common small molecules, on to dust clouds, planets, and stars of various sizes, for our galaxy and a few others that had enough data to be useful. The graph had a long gap between planets (then known only for our solar system) and stars. The writer commented that there was no data at all in this gap, but the two ends did appear to extend to meet each other. So the obvious conjecture was that the distribution continued through the gap, and if so, it would come close to accounting for the "missing mass" needed to explain galaxy rotation.
This was pure conjecture, of course, and since little is actually known about planet formation outside our solar system, it wouldn't be surprising if the actual distribution has dips at various size ranges. But assuming that the gap has the value zero is not very sensible. The obvious approach would be to say that we don't actually know, and Further Research Is Needed.
I wonder if I could find that article again ...
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Wait, so we live in the Milky Way milky? Who's responsible for that naming system?
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I thought they wanted our wimmin.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
A lot of physicists, including Neil deGrasse Tyson, have said that "Dark Matter" is actually a pretty poor name for the phenomenon because it's almost certainly not just some exotic form of matter
No clue who this Tyson guy is but either he, or you, have confused Dark Energy with Dark Matter. Physics is not determined by majority vote but I very strongly suspect that the numbers will come down massively in favour of Dark Matter being an exotic form of matter by which I mean some as yet undiscovered particle. Dark Matter is a very appropriate name for it since it almost certainly is matter and, lacking any electrical charge, will not interact with light at any wavelength. Attempts to explain Dark Matter by modifying newtonian mechanics are vastly more complicated and fine tuned than just adding an as yet unknown particle ever since the Bullet Cluster (and others like it) were discovered. While that is not proof that these models are wrong they fail Occam's Razor and, in general, solutions which fail this test turn out to be wrong which is why it is often used in science to select promising avenues for study.
Dark Energy on the other hand is definitely not a form of matter, for a start it is gravitationally repulsive, and is completely unknown. It is effectively Einstein's cosmological constant but when you use existing physics to try to predict this you end up with a constant 120 orders of magnitude (yes you read that correctly: 10^120) too large so it is safe to say that we are missing something here, even cosmologists worry about discrepancies that large!
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Submission too short.
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The subject novel impressed me with a realistic setting for stories in a relativistic (i.e. sub-light travel only) universe. For how, read the book. One concern I had with its realism was that it assumed many more sunless planets than stars. This article clears that up pending confirmation. Anyone know when this theory started getting serious interest?
No, these "planets" do not have enough mass to even change the amount of visible matter seen in the galaxy, it's less than a rounding error. They are definitely NOT dark matter
No clue who this Tyson guy is but either he, or you, have confused Dark Energy with Dark Matter.
Then you should spend 20 seconds on Wikipedia before making an idiot of yourself in public by not knowing who one of the most famous astrophyscists in the world is. Here's a clue - watch the series Cosmos: A Spacetime Odyssey. He certainly isn't confused about the difference between dark matter and dark energy and I'm pretty certain I'm not confused either.
Physics is not determined by majority vote...
I don't recall anyone claiming that it was.
...but I very strongly suspect that the numbers will come down massively in favour of Dark Matter being an exotic form of matter by which I mean some as yet undiscovered particle.
Based on what evidence? You might be right and it may very well be exotic matter but like you said it isn't a vote. Show me any credible evidence that favors exotic matter over a flaw in the model or vice-versa. Science works on proof so go get some. Until then I remain skeptical.
They're actually the galactic equivalent of potholes. Alien spaceships keep breaking apart every time they hit one.
"If a nation expects to be ignorant and free in a state of civilization, it expects what never was and never will be."
Now that we've finally detected the first of these, we have an excellent idea that this picture is the correct one: it appears that some planets in the local area where we can actually take a measurement are homeless. The broader aspect of our universe's distribution of homeless planets remains completely unknown, as does the explicit state of the local area.
FTF TFS and perhaps even for TFA.
I've fallen off your lawn, and I can't get up.
One day, dear Mars, unless I die first.
So you'll get to Mars unless you don't? That's profound or something.
--
I don't want to rule the world... I just want to be in charge of mayonnaise.
More importantly, it means there is probably something larger than an asteriod to settle on a lot closer to us than Alpha Centauri. Of course we'd need a buttload of reactor power to survive in such an environment.
Someone had to do it.
Oh for mod pointz!
+1 funny!
How much mass would be involved in this population of planets wandering between the stars?
Is it enough to provide an explanation for the orbital mechanics of the galaxy that doesn't require "dark matter"?
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Wouldn't it be possible for a planet to orbit the barycenter of a multiple star system, not just one of the components?
Given that I am a physicist and work on Dark Matter I *very* strongly doubt that.
Really? You work in physics and have never even heard the name Neil deGrasse Tyson even in casual conversation. Perhaps he isn't so famous outside the US but he is very well known even to people with no connection with physics at all. Granted he's known more for his efforts as a science communicator than for his physics work but that's important too. Carl Sagan was well known for similar reasons. Or maybe you think explaining science to the general public is not important? Anyway he's legit even if he isn't "hard core" enough for you. He certainly understands what dark matter and dark energy are. (for the record I get it too - the terms are misleading but I get what they mean)
I'm not in the US, have never seen or heard of that TV program and while I'm not an astrophysicist I can name quite a few and he would not be one of them.
So because you haven't heard of him, he isn't famous? Curious logic you have there.
The fact that I am a physicist, talk everyday to physicists and go to conferences with physicists and I know only one physicist who reportedly believes that DM is likely to be due to a MOND-like effect
The fact that you are a physicist means precisely nothing in this context and you should know that. Appeals to authority don't mean a thing in science. I'm an engineering and an accountant but that doesn't mean I'm always right. The number of people working on one theory versus another means (almost) nothing. That easily could mean a lot of smart people are working on a dead end. That's happened before and will happen again. Show me the evidence (for or against) dark matter being matter versus it being a modeling problem. I don't have any invested interest either way so you won't hurt my feelings. But I'm pretty sure you cannot. Unless it is being kept a secret we don't actually know precisely what is causing the phenomena we call "dark matter" is, not yet anyway. Strong possibility it is matter (obviously) and our models are fine but we can't prove it either way just yet. We simply don't have the evidence as far as I can tell.