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Do 'Ultracool' Brown Dwarfs Surround Us?
astroengine writes "The recent discovery of two very cool 'T-class' brown dwarfs in our cosmic neighborhood has prompted speculation that there may be many more ultracool 'failed stars' nearby (abstract). Not only are these objects themselves very interesting to study, should there be many such brown dwarfs spanning interstellar space. Perhaps they could be used as 'stepping stones' to the stars."
... are 20% cooler than cool dwarves.
Especially if they manage to show a link between this research, the fairly regular extinction events over the history of the planet, and The Nemesis Hypothetical Star...
Do not look into laser with remaining eye.
Yeah, sure. Because when you're on a 100 year cruise to colonize Sirius the thing you really want to do
with your intertia is slow down and stop at your local brown dwarf to pick up a pack of Coke and some cigs.
Does this discovery speed up the Ross 154 - Barnards Star - Sol trade route?
I can't believe how racist slashdot has become. They may be ultra cool, but calling them brown is inciting hate. African American little people is the PC term.
I suppose a brown dwarf might be considered cool in an ironic sense, sort of a reclaiming of both the super-lame color brown and also a traditionally uncool congenital condition. It's the ultimate hipster combination. Especially since all brown dwarfs currently alive to benefit from their new-found ultacoolness were both brown and dwarfy BEFORE IT WAS ULTRACOOL.
I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
I have noticed an increasing number at my local bar lately.
I always thought that Red Dwarf was the coolest...
FTW... http://celebritymound.smugmug.com/photos/329493823_L7DcS-M.jpg
Would these ultra cool brown dwarves serve in putting more fruit to dark matter theories?
In order to have elements beyond carbon one needs a bigger star than our yellow sun. Large stars tend to supernova and become brown dwarfs or black holes in some cases. Some stars fail and become brown dwarfs as well. But you can still get hydrogen from them from solar winds for spacecraft.
It is hard to detect them because the brown dwarfs are Earth size and do not give off much heat or light. Our sun Sol is supposed to have a companion star nearby called Nemesis that is a brown dwarf and throws asteroids at our solar system.
Read this real quick and thought it was an advance report from Comicon...
if your lucky it will have some corn
Tut! Oh God! Why didn't we think of this! It's so obvious! That's where all our research money has gone to waste, assuming that we are omnipotent in our calculations and not including error ranges!
Hell, let's just assume that that 83% (or thereabouts) of all matter in the universe being "missing" is just us overlooking that there might be planets on every star (and the fact that the biggest planet in our own Solar System weighs less than 0.1% that of the Sun).
God, it's so obvious. Why did we never take this into account in any of our billion-dollar-funded research programs filled with (quite literally) rocket-scientists?
Or maybe we did, you pillock...
I know I'm a layperson, but I think astrophysics really needs to move beyond the assumption that if we can't see it it isn't there. The more closely we're able to study space the more we find that it's full of stuff of every size at every conceivable distance. I honestly thing it's safe at this point to assume that nearly every star has planets as a simple matter of the nature of stellar accretion processes, and further that for every star that's bright enough to see there are probably a dozen too dim. This is why we can't figure out dark matter/energy.
If the arrangement of discovered exoplanets has taught us anything, it's that most of our safe classic assumptions need to be wadded up and thrown in the nearest dustbin. And yes you are a layperson who probably knows nothing about the practice of astronomy or astrophysics, or high energy physics. It's not a matter of "seeing" or 'not seeing". If something exists it makes it's imprint, it's footprint in the universe around it, in the gasses it's thrown off, it's interaction with other things or just the presence of it's gravity. Astronomy does not make simplistic assumptions like the one you put out. Right now it's about building the best possible model to fit the observations we make now and predict what we'll make in the future.
...hip hop, don't listen to it.
P.S. we infer most of the mass of the universe through the movement of things we can observe (because all mass bends space-time) - and we get a pretty god-damn accurate picture of what MUST be in it's local neighbourhood for it to act like it does. The fact we can't see the mass itself is neither here nor there - we're literally looking at how a galaxy (BILLIONS OF STARS!) behaves and inferring how much it and it's surroundings must weigh in order to act like that. There's about 170 billion galaxies to look at.
On those scales, extra planets and a few missing stars don't even factor into the error ranges because they are so inconsequential. Hell a couple of extra galaxies doesn't even register.
We surround them.
I dunno, but a "brown star"... that shouldn't be too hard, should it?
The problem is, if we can't see it, how do we know if its there or not? You can speculate, of course, and a surprisingly large amount of astrophysicists do precisely that. That's pretty much what "dark matter" is: pure speculation about something we can't see and haven't yet directly observed, but which happens to fulfill a certain role in our theory of the universe. This has the obvious problem of being rather unscientific: until we devise some method of testing for its existence, we can't, empirically, say it exists. Its not completely unscientific: it might be possible to prove it doesn't exist, in the form we currently envision it. In which case scientists basically just tweak the numbers till it can exist. Not a criticism: that's kind of how science works.
However, without some positive evidence, we can't simply assume something we can't see exists. You mention assuming every planet has stars. Of course, many of the ones we've observed do, but there are very many kinds of stars, and its a safe bet that entire classes probably don't have planets. Stars that formed early in the universe, for instance, might not have been able to form planets because of forces from other stars. Or stellar winds that some stars produce might have blown away all the material needed for planets. The possibilities are endless, and if we simply assume things without proof about the way the universe works, we can basically kiss all the knowledge we have of the universe goodbye. The key to any assumption is to first prove or disprove it, then move to the next assumption.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
I've never seen a negro midget, let alone a cool one. Maybe in California?
Do you even lift?
These aren't the 'roids you're looking for.
...Me, Myself and Irene popped into my head.
The idea of Y-class brown dwarf stars are neat and all, but this whole 'stepping stone' idea is not really explained. Why would we use these as stepping stones? Is there an advantage to it? I don't understand why we would use them is all.
I call it 'The Aristocrats'
Suddenly it all makes sense: we're surrounded by assholes. Still, it doesn't take a scientist to realise that.
That's racist.
This is the problem, you think that just because stars are so massive that it makes all the other smaller masses irrelevant. Yeah, 0.1% doesn't seem like much in one instance, but if there are a thousand you can't see then you have, albeit distributed, a solar mass that you can't see. And then multiply that how many times? Billions? Trillions?
The fact that we can't even prove or disprove that a brown dwarf orbits our own star demonstrates that our 'accuracy' about our local neighborhood can't be all that good. If we can't see something that massive when it is relatively right in front of our face, there could be an innumerable amount of them floating outside of any obvious gravitational influence on other bodies.
Smaller masses in the universe almost certainly outnumber the larger masses exponentially. Just look at the contrast between giants and dwarfs in the stellar catalogs. Would you discount dwarfs because they are so relatively less massive than supergiants? Of course not, there are too few supergiants and too many dwarfs to do that. So why do you discount all the unseen sub-stellar material? When you see these patterns of scale, failure to extrapolate is irrational.
I support the Slashcott and will not be reading or commenting from 2/10/14 to 2/17/14. Beta is steaming pile of dog shit
They're finally, going to get some diversity into Snow White?
In 3...2...1...
Yeah, the next thing you know something like this is going to happen. It's just a matter of time, I tell you!
UNIX? They're not even circumcised! Savages!
Yet another place the JWST (James Webb Space Telescope) would be fantastically useful!
Also, how seriously would the presence of previously undetectable ultra-cool stars affect the search for dark matter? Aren't we looking for energy/matter based off some energy level, and might that mass be tucked away in the form of ultra-cool stars, just to cool to detect?
Learn to significant digits.
I've suspected this since Gary Coleman and Emmanuel Lewis were first detected in the 1980s.
http://alternatives.rzero.com/
Q. What are the odds that 50 yrs of technological progress would slash the stellar travel time, so that a 100-yr trip would likely be pointless?
The number of extra planets or dark stars you would need to matter, *would* show up because there would need to be soo many. They have been looked for you know. For example if there are millions more of these cold brown dwarfs than what we already have estimated, then the average distance to them would be so small that we would be able to observe many of them (probably would imply at least a few within the ort cloud). We would see many more micro-lensing events ... etc etc.
You can't have your cake and eat it too. If there is enough to explain dark matter, there is more than enough that observing them would be quite trivial.
On top of all that, such objects do not explain other observations of dark matter. In particular, the bullet cluster. We can in fact "see" dark matter.
If information wants to be free, why does my internet connection cost so much?
Evidence: The bullet cluster. The observations imply that there is a huge amount of mass that was moving with each galaxy before the collision, that is not baryonic. That is interacts only via the force of gravity and is not affected (or at least very very weakly interacting) via the other forces, most importantly the electromagnetic force.
There is quite a few other effects that dark matter can explain nicely. We are in fact devising experiments to attempt to observe dark matter particle candidates.
If information wants to be free, why does my internet connection cost so much?
So (like another poster) I'm not sure how useful these would be as refueling dumps (stepping stones). I mean, once you've gotten a starship up to speed then slowing it down to refuel just to speed up again just doesn't make sense. I guess the only use would be if there were consumables that could be obtained for "generation ships" or if some large piece of the ship needed repair material (as in the ice shield on the starship in Arthur C. Clarke's "The Songs of Distant Earth"). I guess they might make sense if they were power stations that could beam (lasers?) energy to a passing ship.
Another (briefly discussed) issue is that of missing matter. I realize that the amount of planetary matter must be a negligible contribution but why couldn't there be 100s or 1000s of brown dwarfs for every sunlike star? Is it because we'd see a lot more microlensing events or our Oort cloud would be perturbed much more frequently? It would be kinda cool if there were much more of these things out there rather than stuff we can't interact with.
Are there any "habitable zones" around them? Sure there wouldn't be any light but it'd be like being next to a nice campfire for some really close orbits. Would the orbits be too close and decay in a geologically insignificant amount of time?
If we ever got fusion drives (but nothing better) maybe having lots of these things would allow galactic expansion as a long slow crawl at very small fractions of the speed of light. In which case setting up colonies of couple thousand AUs over many millennia could gradually establish a dark web between the brightly lit stars (so much for Star Trek). These bodies then wouldn't be waypoints. They would be our homes.
If you're going to deride somebody's phyisic-fu in a post about rocketry, it is absolutely mandatory that you follow the New York Times style guide on being a total pompous ignoramus, to whit:
<X> seems to lack the knowledge ladled out daily in high schools.
-- NYT editorial, 21 January 1920
Note, there is a customary 49-year window to admit you didn't know what the fuck you were talking about. Although a more honest person would give it up when missiles start falling out of the air onto London.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
Fonzie-1, Fonzie-2, Fonzie-3...
To our current knowledge the gp is right : it is truly never. From the antiuities to now, we have refined our knowledge of physic, but we never removed limitation. We keep adding them on. For example newtonian mechanic allowed speed greater than light. Now to our knowledge it is an absolute limit. The more I learn in physic, the more limitation come in, and the exception to the rules come in extrem cases : extremly high pressure, boson condensate, low vaccuum and vbery short distance, but even those exception respect the primordial speed limitation. So barring an incredible discovery (a possibility which cannot be discarded but has about as much probability as a second coming), the GP is right. never is long, but sadly for this universe, an extremly likely bet.
Astrophysics moved beyond this over a century ago. If you knew anything about astrophysics or astronomy you would have known this. Granted, this kind of thinking predates even this event but this is probably the best known tale in astronomy of someone knowing something existed without direct observance.
And I must also point out that it's great that you show some level of interest in this kind of thing. While I don't think you should need to have a PhD in astrophysics to discuss it you should still get some base knowledge of what you're talking about before making grand statements of this nature or making assumptions that are plainly false. You really should take the time to sit down and study up a bit before coming off like a jackass. I recommend AstronomyCast for starters.
And I'm really not trying to be a smartass but the resources to have a basic understanding of these types of things is so easy to get to and most of them are free. It's a shame to go around looking like a fool for it.
What, an army of midget JJ " Walkers?
"Flyin' in just a sweet place,
Never been known to fail..."
So these brown dwarfs are essentially big balls of (mostly) hydrogen with the centers under tremendous pressures and temperatures but not quite hot enough to "light" (in a fusion sense). Well what would happen if you managed to drop a fusion bomb on it? (On or near the surface where the temperatures are low but the high gravity might still compress the hydrogen into the megabar range).
While (probably) it would just fizzle, could the concentrated energy ignite just enough so the whole star went boom? (Like a Type I supernova?). I mean the "temperature" of an H-Bomb is in the hundreds of millions of degrees maybe it just requires one tiny (if an H-Bomb is "tiny") spark. Just like you can pour millions of gallons of gasoline on a barely sub-critical mass of Uranium and it won't go bang but one small neutron generator and you've got a mushroom cloud. While the impacts of asteroid and larger bodies could deliver a lot more energy, an H-Bomb could do so more INTENSELY.
I guess this is what the first H-Bomb scientists were worried about when they feared the first H-Bomb *might* ignite the water vapor in the atmosphere and consume the entire world. Just how easy would it be to blow one of these things up? Could you do it with even smaller cooler less dense bodies, say Jupiter (as proposed by sci-fi writer Charles Sheffield) or Neptune? (Tried it on earth, nope doesn't work). Lastly, our sun is already alite, but the RATE of fusion reaction is very slow (each gram of the sun produces far less energy per time than, say, a live elephant). Could we speed it up? Could an H-Bomb (or a suitably powerful laser such as was used in one of the Man-Kzinti war sci-fi books) trigger a local (or maybe not so local) explosion?
I guess this was the general idea behind the movie "Sunshine" (good movie). Seems they had some sort of very dense (causing a local gravitational field) fission bomb to re-ignite the sun. Wish they had a companion book to flesh out some of the details.
Anyway I know these ideas are probably non-sensical to any physicist but don't have enough math and physics knowledge to calculate it for myself. If anyone of you is so inclined and it won't take much time or effort, I'd appreciate the debunking (or not!) of this idle speculation.
(For even crazier speculation, how about igniting all that supposedly great fusion fuel Helium-3 that is just lying around on the lunar surface? Would it be enough to blow the moon out of orbit a la "Space 1999"?)
I am reminded of the voyager series space probes, that used Jupiter's massive gravity well as a slingshot to reach saturn, and from there, Uranus and Neptune. (Also known as the "Grand Tour".) The mission was possible because of a rare orbital configuration that only happens once every few hundred years.
In this case, we would launch a probe pretty much directly at our sun, use the sun's gravity to accelerate the craft much faster than chemical rockets would normally be able to handle, then swing around the sun towards one of these brown dwarf stars. The probe would slow down as it left our solar system due to interaction with the heliopause and heliosheath of our own solar system, and later that of the brown dwarf it would interact with.
If we presume that these "nearby" objects are closer than our more luminous neighbors (There are 3 systems that are within 7 light years distance...), it might only take a few decades to reach one, instead of a few centuries to reach one.
Everyone knows that Willy Wonka ended up inviting them to work at his factory and get away from their natural predators.
Oompa-Loompa come from Loompaland, which is a region of Loompa, a small isolated island in the Atlantic Ocean. The Oompa-Loompa would end up being preyed upon or attacked by Whangdoodles, Hornswogglers and Snozzywangers, which also lived there. Oompa-Loompa are only knee-high, with astonishing haircuts, and are paid in their favourite food, cacao beans, which were extremely rare in their island. Oompa-Loompa insist on maintaining their native clothing. Only the male Oompa-Loompa are seen working in the factory
Admitedly, the Oompa Loompa are "ultracool", but I think the agreed color of their skin is typically refered to as "orange".
Like ghosts and deities, presumably?
"I think astrophysics really needs to move beyond the assumption that if we can't see it it isn't there"
Disclaimer: I am an astrophysicist and I get the impression one or two others replying to you either are, or are very well-informed laymen themselves.
My brief comments: Firstly, there are plenty of people - thousands of them - who are highly educated and thinking about this professionally. Not meaning to sound arrogant, but it's pretty damn unlikely that you'll think of something that someone else hasn't, studied in detail, and constrained against data. No offense but the fields in which a layman can significantly impact against a few thousand highly trained professionals are pretty limited. It's not impossible... but you have to be at least as highly trained, as Einstein was.
Secondly, since when has astrophysics assumed that if we can't see it it isn't there? You're even referencing dark matter... and the standard assumption (notice "standard"; it's not the only assumption made and better models are tested constantly) is that we can't see it and it is there.
Refueling... Even with the best drive, you don't want to carry all your fuel with you. A quick circling stop there could boost speed and pick up more fuel, not to mention much needed gravity vacation.
I8-D
It's off-topic but you *can* fit the bullet cluster with a theory of modified gravity and at least one species of massive neutrinos (and we have at least two species of massive neutrinos in nature) so long as they're sufficiently massive. It was a major blow against TeVeS that it couldn't fit the bullet cluster... and then it was found that actually it could if you add in a well-motivated species of warm dark matter which is definitely in existence.
This shouldn't be taken too strongly. I don't think anyone really believes that TeVeS is the be-all and end-all, and you do need quite a bit of mass in your neutrinos. But it does show that the bullet cluster isn't necessarily immediately the death-blow for non-particulate dark matter it was initially announced to be.
I have presented to several of my friends/coworkers/family the idea that interstellar space IS NOT the great void we seem to have been assuming for so long, but instead may well be filled with all manor of significant objects, including brown dwarfs, rogue planets, etc. We don't have to make some multi-lightyear jump across nothingness to reach the stars; we can jump from world to world to world, like a great migration wave-front, gathering resources and establishing waypoints as we go. It was an article in Analog SF magazine that got me thinking along these lines. It may take generations to reach the next major star, but at least there will be fun exploration along the way.
VASIMR to Mars!
Everything is relative. It shouldn't be too difficult to find a brown dwarf heading somewhat in the correct direction. You'd have to spend some fuel to match the trajectory, but with judicious selection you could minimize that.
Weaselmancer
rediculous.
Changing gravity and requiring massive neutrinos seems like the antithesis of Occam's razor. I was never a huge fan of dark matter. But now its really hard to say its not the best explanation with a straight face.
If information wants to be free, why does my internet connection cost so much?
star formation results in a range of star sizes. some sizes are below ignition threshold. we don't see them, simply because they're dark. but, statistically speaking, there should be a lot more failed stars than ignited stars. so take a random section of space, count the number of stars you can see in that, and there should be a mathematical relationship between the number of visible stars, and the number of invisible unignited smaller "stars". and this relationship should be proportional by orders of magnitude. say: for every 10 stars you see, there are 1,000 unignited balls of hydrogen sitting out there in the dark, undiscovered, and to, some extent, undiscoverable. even transit in front of distant stars would be fleeting and one time only affairs
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
And yet, given the fact that these smart people number in the thousands, probably much more, and that there is no indication that we've missed some big chunk of physics or chemistry, there are *still* people who cling desperately to the sci-fi fantasies of space colonies and all the other rot from garbage sci-fi.
Instead of being mature and sensible and making better living arrangements right here, right now, with real materials, real technologies and real people, they go off into a Space Nutter psychotic state, denying reality completely.
Is it any wonder Space Nuttery will be a diagnosable mentall illness in the DSM-V?
Well, not really. If you're invoking Occam's razor, GR itself violates it horribly compared to Newtonian gravity... unless you look at it a particular way. I mean, who the hell wants to change
* F=m_i a /r^2
* F=G M m_g
into
* G_\mu\nu=\kappa T_\mu\nu
where \mu and \nu each run from 0 to 4? High-school maths into university level maths? It's only if you look at it from the level of an action that it looks so simple...
Personally I feel adding in extra matter fields that are unmotivated other than SUSY (which is itself a horrific violation of Occam's principle unless you look at it the right way - the "right way" being some symmetry arguments based ultimately on group theory) and are barely motivated there is less palatable than accepting that Einsteinian gravity is potentially flawed, and our application of Einsteinian gravity *certainly* is. (It is. The open questions are just how inaccurate our calculations are. Most likely, the errors are insignificant, but this has to be checked before we run around adding a million scalar fields - none of which have been observed in nature, by the way - and Lord alone knows how many supersymmetric or otherwise exotic matter fields into things.)
Basically, if you assume Newtonian gravity, you're driven straight off to a particle explanation of dark matter straight off. But Newtonian gravity is wrong. Then if you accept GR -- and that Newtonian effects are insignificant on galactic scales -- you're also lead to a particle explanation of dark matter. But that's an *assumption*, that relativistic effects are insignificant. They probably are, but if we model the galaxy more accurately, in a cylindrical metric, we get some effects that look a bit like dark matter. It's not enough and the best calculations are still very speculative (even the most firebrand only claim about 33% dark matter this way) but it's still... indicative. If nothing else, why the hell are we adding in arbitrarily new physics before we properly understand the current physics?
Then, let's assume you can only get a 5% dark matter effect from relativistic effects, which I feel would even then be optimistic. People immediately run, again, to a particle explanation for dark matter. But why the hell are we so sure that GR is right? Why do we keep a theory which is actually still fairly poorly tested, in favour of modifying a theory that's relatively well-tested in our particle accelerators? Put it this way: we've tested GR/Newtonian gravity on scales between about 10 micrometres and the bounds of the solar system. Then we extrapolate that up a few orders of magnitude and pretend it's applicable on galactic scales. Then we extrapolate up *another* six orders of magnitude and pretend it's applicable on cosmological scales. Then we express surprise that something doesn't quite work.
Maybe GR properly describes gravity. But we haven't actually tested that! And observations disagree with the assumption. Do we... invent things to explain the observation, or do we at least question our theory of gravity? Do I add in a bunch of unobserved superpartners simply because one of them would be a stable dark matter particle, or do I slightly modify a potentially inaccurate theory of gravity? Personally, I want to check both. Unfortunately a lot of researchers are focusing on the former, not least because a large number of themare better than I -- much, much, much better than I -- at particle physics and at observations assuming Minkowski space, but worse than I at relativity.
Anyway, that was a long rambling rant :) But I just feel that adding massive neutrinos -- and neutrinos *are* massive; there are at least three species, and at least two of them have mass. If we believe any of our current particle physics, that is unescapable -- and modifying gravity is preferable to adding a plethora of unobserved arbitrary fields and tweaking one of perhaps 130 free parameters. Others feel differently and may very well be proven right, in which case excellent. At least we've also exhausted alternatives.
Provocatively stated but I do tend to agree anyway. Well, except the stuff about the DSM-V. Also I think these Space Nutters themselves number in about the hundreds, and are pretty much harmless.
No.
And further, maybe someday we'll also be able to tap zero-point energy and create matter and energy in the middle of apparently empty space.
http://en.wikipedia.org/wiki/Zero-point_energy
I can wonder if planets and asteroid orbiting brown dwarfs far away from the turmoil of the galaxy and other stars might be and ideal place for life, same as there is a lot of variety of life in the rarely disturbed deep ocean. The closer you live to a galactic core, the bigger the chance for periodic supernovas and superwaves and whatever else that may wipe out all life in some area.
We'll probably have suspended animation and "mind children" and lots of other approaches to galactic panspermia someday, too. Still, I feel we should clean up our act on Earth first, so we don't take a lot of stupid and ironic problems with us to the stars.
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
Thanks for the speculations, and I'd encourage you to try some back on an envelope order-of-magnitude calculations to see which might make sense. For example, get a figure for the energy of an atomic bomb in some unit, and then find out the energy the sun puts out in one second in the same unit, and compare them.
Also, what may seem to make sense with today's physics might seem ludicrous with tomorrow's physics.
Maybe the sun is indeed a ball of iron.
http://www.thesunisiron.com/
Or maybe cold fusion takes place at the Earth's core at the edge of a nickel-iron core?
http://aleklett.wordpress.com/2011/05/16/the-sun-rossi%E2%80%99s-%E2%80%9Denergy-catalyzer%E2%80%9D-and-the-%E2%80%9Cneutron-barometer%E2%80%9D/#comment-5891
Or maybe we will tap zero-point energy reliably one day?
http://en.wikipedia.org/wiki/Zero-point_energy
Or the universe is mostly shaped by electrostatics?
http://www.electricuniverse.info/Electric_Sun_theory
Or the universe is a simulation:
http://www.simulation-argument.com/
And so on.
"Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand. (Albert Einstein)"
Hope you keep imagining things. And think about ballpark calculations. And still hold on to your "roots" in humanity and day-to-day things like sunshine, vegetables, and laughter even when having imaginative "wings".
A 21st century issue: the irony of technologies of abundance in the hands of those still thinking in terms of scarcity.
Well on the face of it GR is defiantly not "better" than Newtonian physics. But it does fit the data better and passes every test we can throw at it. Even frame dragging! However even in my original department GR effects at a galactic scale where often considered as a candidate. But every time the sims are run or approximations made for pen and paper... the results where never even close to enough to explain galactic rotation (not the only thing that can use dark matter as a explanation).
As for adding new physics before understanding what we have. Well yea of course. Otherwise we would never move forward. Both GR and QCD are not easy to solve in any non trivial setting, that is not a good reason to stop until we can. Just assuming that everything must be wrong at some scale because we can't test it there seems just as disingenuous as invoking a matter field. In fact the matter field seems better because at least you may be able to make some new predictions that can be tested.
Lots of us don't like dark matter any more than the standard model. But they just work. Ok so dark matter is a shadow of the standard model. But its still the best we got. Every modified gravity theory i have seen either only works in one case or not at all, and the only motivation is to explain that one effect and hence have zero new predictions other than fixing one observational issue. Dark matter is just better right now. Got something that works better. There are lots of us that will be all ears.
If information wants to be free, why does my internet connection cost so much?
Stars such as the sun don't go boom just because a fusion reaction is going on. And they are capable of sustaining a fusion reaction.
What you would get dropping an H-bomb on a brown dwarf is an unsustainable fusion reaction. It would go boom, not making much of a dent in something the mass of a brown dwarf. Yes, it would have an energy release larger the bomb itself would give, but not enough to ignite/sustain ignition of the star. Sorry, no supernova.
The impact pressure of random asteroids (or rather, similar space rocks) is orders of magnitude higher than that of our puny human atomic weaponry. The short version is, "If it can happen, it's probably already happened, and if not there's not a whole lot we could do about it anyway."
There is a possibility that we could find a "virgin" brown dwarf that's right on the knife's edge of fusion, but given the size of these objects there's no reason that the fusion would take it all over at once anyway.
So, what you're saying is that all we need to find these brown dwarfs is a smelloscope?
The Christian Right is Neither (Christian nor right). See: Matthew 23, Matthew 25, Ezekiel 16:48-50
Gary Coleman or Emmanuel Lewis?
A meteoroid with enough impact power to equal the largest nuclear bomb we have ever made impacts the earth roughly every thousand years or so. So, any brown dwarf that could be ignited by a bomb would be ignited already by stray impactors.
I suppose one could set up a scenario where a bd had, over the eons, been heating up little by little due to external forces and was now only one bomb away from ignition. But again, if it were that close to going stellar, then any ol' starquake, or maybe even tidal forces from a revolving moon, would probably set it off. And even in that instance, my totally wild-ass-guess is that it would be a localized explosion; that it would be essentially impossible to set things up such that a brown dwarf could go completely nuclear from a human level event.
There are two kinds of people: 1) those who start arrays with one and 1) those who start them with zero.
Well what would happen if you managed to drop a fusion bomb on it?
I get the impression this isn't the first time you've asked that question.
As ultracool as it gets.
Yeah.. but we're adding new particle physics on the understanding that Newtonian gravity is sufficient. It's not. We're also doing so on the understanding that our application of GR is also sufficient. It's not. I'm not a galactic dynamicist; I'm a cosmologist. The dark matter in my field is seen in the Friedman equations which, regardless of whether they're valid or not, are from a naive application of GR on (at least) Gpc scales, assuming homogeneity and isotropy. This may or may not actually be valid, not least because it involves a whole collection of undefined uses of the phrases "on average" and "on large scales". Assuming "on average" that the universe is homogeneous and isotropic does lead to the FLRW metric; that's true. Maybe that's even actually a true assumption and that "on large scales" FLRW is an accurate description of the universe -- but even if that's true it's only true for null geodesics and it *isn't* true for the dynamics. The Einstein equations are non-linear, or they'd just be a rephrasing of Newtonian gravity. That non-linearity means that regardless of whether we can talk about "average" quantities in GR (and, currently, *we can't*), and regardless of whether FLRW will hold "on large scales" (and it may very well do and I suspect it does), the dynamics are different from FLRW dynamics.
Quantifying that is, of course, a different matter. Interestingly, so far, the deviations in the dynamics using a naive definition of a scalar average and a rather unsatisfactory averaging on 3-surfaces, have tended to look like dark matter. Does that solve the (cosmological) dark matter problem? Of course not. It would be bizarre to claim it did. Does it suggest that there may at least be something in this idea? Yeah, sure.
But more than that, you can go the other way and avoid questions of averaging at all. Instead, you can take a look at the effects of inhomogeneities in GR. That's remarkably ill-researched given that we tend to stick in Schwarzschild, Reisser-Noerdstrom, Kerr and FLRW metrics (three of which are inhomogeneous). Sure, people are putting in LTB metrics in cosmology now,and a few people are using Szekeres solutions, but it's very under-studied. And if you like dropping the Copernican principle (which many don't, myself included) you can drop a requirement for dark energy, at least.
I don't have a strong point here, but the relativistic effects in cosmological (and astronomical) systems remain badly understood. We work with strong assumptions -- in cosmology, that FLRW is an accurate description and in astrophysics, that Newtonian gravity is applicable -- and very rarely question that properly.
In reality I suspect the "answer", if we ever find one, will be a mixture of things. Will SUSY turn out to be true? God, I hope not, but quite possibly it will. Then that gives us a dark matter particle. Are neutrinos a dark matter? Yes, that's incontrovertible. Are relativistic effects (from inhomogeneities, for instance) significant? Yes, I strongly suspect so. Are seemingly arcane theoretical arguments about averaging actually significant? Yes, I suspect that, too.
I wouldn't say "Dark matter is just better right now". I'd say "a naive model where you put in a totally pressureless fluid is a reasonable approximation to reality but still has issues". LCDM is struggling with a few oddities, with large bulk flows, a seemingly never-ending tower of structures on ever-larger scales (not virially bound, just *there*), remaining issues (on a naive dark matter model) with galaxy formation, cusps at the centre of galaxies, an under-abundance of small satellite galaxies, and a few other issues. On the other hand, while no-one, Milgrom included, would pretend that MOND is anything other than pure phenomenology, you surely have to admit it's pretty fucking impressive that such a simple modification of gravity can fit the dynamics of galaxies at least as well as a collection of dark matter halos. Sure, MOND dies on cluster scales, and very badly. I'd never pretend it's anything other
Even on a successful star, no fusion occurs in the outer layers. So If I had to venture a guess, I'd say the the "surface" of a brown dwarf would be far too diffuse to support a fusion chain reaction even with an ultra powerful fusion bomb as an "spark". So to have any chance, you would need to get your big fusion bomb much closer to the core, which would be an impressive feat given the intense pressures that it would have to withstand. I'm not saying it would be impossible, but we'd be talking about pressures several orders of magnitude higher than what we have at the floor of the deepest ocean trench.
Maybe there is a very LARGE oxegen tank near UrAnus?
I hope if one is found nearby they will name it Hyundai +4904/-56.
...these objects represent some of the "dark matter" we are searching for?
It doesnt actually matter how many Brown Dwarfs we have missed
There are limits on how much "ordinary" (Baryonic) matter there can be, regardless of how much we actually have down on our named list here. So no matter how much we have underestimated the number of Brown Dwarfs (and we have done a pretty good job on estimating those numbers, that is what I was doing for my PhD pretty much 15 years ago and even then it was getting obvious that Brown Dwarfs or similar was not the answer) the fact remains that they cannot account for any significant proportion of "dark matter"
As regards "if we cant see it it isnt there" surely astrophysics actually assumes the opposite. Namely that there definately is something there but we cant "see" it. Hence the term dark.
I find it amusing that everyone in this thread seems to think that we're anywhere *near* the technology for a propulsion system needed to journey to another solar system in a mere 100 years. The fastest we've ever accelerated any object in history (the New Horizons probe) would take more like 80,000 years (and that's just to get to the nearest one, our galactic next-door-neighbor at just 4.2 light years away). And that's not even factoring in added time for the deceleration you would need to actually stop once you got there.
We would have to get to a significant fraction of the speed of light to even dream of getting to another solar system in 100 years. And, so far, that tech only exists in the minds of science fiction writers.
SJW: Someone who has run out of real oppression, and has to fake it.
It doesnt actually matter how many planets or brown dwarfs you think we have missed
There are limits (for very good and well checked reasons) on how much ordinary (baryonic) matter there can actually be
We may have understimated the numbers of extrasolar planets or similar but that still wont account for the vast majority of the missing matter. In any case such calculations have been well looked at for a long period of time and screwed down pretty tight (this is what I did for my PhD almost 15 years ago. Even then it was pretty clear that brown dwarfs were not the be all and end all of accounting for dark matter within galaxies).
Regarding "move beyond the assumption that if we cant see it it isnt there"...surely that is the whole point of dark matter/dark energy. We are confident that 'something' is there, but we cant 'see' it, hence our insistence on using the term 'dark'.
and they're stealing my underpants...
I'm still fighting against people who think that because they have pocket computers that somehow materials are stronger, fuels more energetic and space smaller than before. The violent, insane and psychotic lunacy at work here has to be controlled. Hopefully I can even cure some of them.
Space Nutters are harmful and even hateful, because they misinform the public, and take the credit away from the true sources of technology that we have today. They are deranged individuals, with no sense of shame, no sense of decency, and no sense of "orders of magnitude", they are ignorant, arrogant, childish and petulant little liars who have no problems lying to advance their little fantasies.
They think owning the Star Trek box set is a good education in physics. They think the space hogwash sci-fi from the 1960s is documentary, and not fiction. Still think they're harmless?
To be honest, I have no idea what the "DSM-V" stuff is referring to. The people I've encountered like this... harmless. Sometimes annoying, but harmless. Asking me weird questions at conferences, but harmless. I don't care if people believe NASA claims it invented a lot of current technologies. In some cases it's even got a point, and in the rest, people can believe what they want. There are plenty of people believe that moon landings never happened - and I'm willing to believe that there are as many of them as the bonkers-crazy space nuts you're talking about. Some I've met are even actually extremely intelligent and better than me at vast swathes of physics, and yet believe the moon landings never happened. And even these people don't have really much impact.
Ultimately, yes, I believe they're harmless. People who believe them can be reeducated. Those that can't were probably useless in the first place. And no-one has ever found any use for bizarre crazy 60s sci-fi fans who think its all real. Thankfully they don't receive government grants.
So these brown dwarfs are essentially big balls of (mostly) hydrogen with the centers under tremendous pressures and temperatures but not quite hot enough to "light" (in a fusion sense). Well what would happen if you managed to drop a fusion bomb on it?
"Fusion" bombs fuse Deuterium and Tritium. Brown dwarfs already fuse Deuterium and Tritium for the part of their life cycle. That's what makes them brown dwarfs and not planets.
http://cronodon.com/SpaceTech/BrownDwarf.html
In order to create a real star, you need proton fusion. But that requires maintaining necessary heat and pressure for millions of years. If the gravity of the brown dwarf and the native deuterium and tritium couldn't do it then it is unlikely that your puny little H-bomb is going to accomplish much.
http://www.tim-thompson.com/fusion.html#ppcycle
Please stop before you hurt yourself.
We know roughly how much the galaxy weighs (although that number has some pretty big error bars and is refined on a regular basis). We've got a rough idea of how much luminous matter (stars) there probably is in the galaxy by extrapolation (we can't see the whole galaxy), and we can't even see all the luminous matter, especially that's even a little ways away. Astronomers are very aware of this.
Nevertheless, gravity provides a pretty good way of measuring the mass of things and lots of other evidence, including the distribution in masses of objects we can see, models of the generation of matter in the big bang, and the physics of star formation (anything big will ignite fusion and burn, a high density of little things tend to collapse into a star).
You might want to consider the idea that you could learn more by asking questions rather than stating an uninformed opinion, sticking to it as fact, and implying you're right where thousands of highly educated professionals who have dedicated their lives to understanding these things are wrong.
Ah, modified gravity gets better and better.
To fit the data (ALL the data) you need to modify gravity, have neutrinos with an unlikely amount of mass AND have non-baryonic dark matter.
Or you can just have non-baryonic dark matter.
You don't understand Occam's razor.
Newtonian mechanics is simpler, but doesn't explain all the data. Relativity is more complex, yes, but it DOES explain all the data. The principle of parsimony suggests that if we're presented with two explanations that both explain the observations then we pick the simpler.
If you just modify gravity it's arguable whether that change is simpler than postulating non-baryonic dark matter or not. But modified gravity doesn't explain the observations. You have to modify gravity AND have dark matter. Or you can just have dark matter. Both explain the observations.
No. The problem is not that they're cold, it's that they don't have enough mass to produce the necessary pressure. If you could somehow heat up the whole brown dwarf all you'd end up with is a puffier brown dwarf.
Fusion reactions require pressure to squeeze the reactants together hard enough to fuse. Getting them very hot can help (the atoms ram into each other harder) but only if you have some mechanism to contain them.
the new oompa-loompas. They're everywhere.
"I've never seen a negro midget, let alone a cool one."
I don't know his name (too lazy to look it up) but I thought the guy in Bad Santa was pretty cool.
Maybe not oxygen, but definitely some kind of gas!
Thanks for the awesome post. I'll have to check out "Sunshine." I have to wonder why it hasn't been explored more in Sci-Fi. If you could force a large coronal mass on the side of the sun way from us you could catch the energy in a solar sail. On might even get a large fusion reaction by detonating an H-bomb in the corona of a brown dwarf, Your main problem would be intense gravity and currents since brown dwarf are believed to be below 250C. One might get a large mass release from a brown dwarf. This could be used to has power and heat or to boost a new solar sail. I don't think we could start a fusion implosion that would start a brown dwarf. And if we did it would probable heat up and expand outword till it cooled down. Then again it might take thousands of years for it to cool back down.
I think our best bet for for exploring beyond our solar system is to catch rides on stars as they pass close by us. Rinse and repeat if we can survive long enough we might be able to do it. I think it is our natural goal to continue to expand as that is what life does. Remember the universe isn't beautiful if no live exists to define beauty.
Beetlejuice from the Howard Stern show!
If you're trying to claim that non-baryonic dark matter fits "Occam's razor" better then you also don't understand it. *It doesn't exist*. You have to have a proper, working model, and that model is going to be just as ugly and ad-hoc as modifying gravity. The MSSM is an ugly collection of assumptions. A modified gravity theory is typically an ugly collection of assumptions. Just saying "aha! a single pressureless particle fits everything!" doesn't work because it's not a physical model - it's a phenomenological one.
This is getting ridiculous.
What part of "this shows that in principle a modified gravity can explain the bullet cluster" says "MODIFIED GRAVITY IS TRUE AND IT'S TEVES!" to you?
A) Neutrinos have mass. Are you arguing that? If so, this conversation is over now.
B) Given that neutrinos have mass, they act as a warm dark matter no matter what the theory of gravity. Are you arguing that? If so, this conversation is over now.
C) Given that neutrinos act as a warm dark matter it should be taken into account.
D) Adding massive neutrinos into one particular example of a modified gravity (TeVeS) demonstrates that it can fit the bullet cluster. The details are unimportant because no-one in their right mind is pretending that TeVeS is a good theory of gravity; it's an ugly ad-hoc collection of fields.
What's your problem here?
Let's throw open a suggestion here: imagine a universe where GR is inaccurate and is modified in the infra-red. This universe also contains massive neutrinos. It *also* contains something similar to MSSM with a stable lightest supersymmetric particle. Then let's put "ceoyoyo" and his amazing abilities at physics into this universe. Rather than understanding what's there, the mighty ceoyoyo will attribute everything to a non-baryonic dark matter (evidently not even caring to link it to his supersymmetric particle but let's say he does that, too). Then he'll find that things are inaccurate, because that's not the whole story, and invent another particle to make it work, and then he'll relax, happy. And ignorant.
I strongly suspect that that's the universe we live in. I'd love it if MSSM was wrong and there's nothing of hte sort but I'm not silly enough to actually believe that. It's a complicated place out there. We can either describe it properly, or we can make snide little comments on internet forums mocking anyone who doesn't want to restrict themselves to some unspecified "non-baryonic dark matter".
All very good points. I don't really disagree with anything. Except perhaps i thought that current mass bounds on neutrinos means they are not really candidates? But i have been out of the loop for a while now.
If information wants to be free, why does my internet connection cost so much?
Or what if you were to crash two brown dwarfs together? Could that tip them from not-quite-enough-mass-to-burn into KaBoom?
Short answer is: Maybe. Deuterium could potentially collect in a chemically distinct high density layer inside a brown dwarf. If we could hit it with enough energy to start a burn wave then the whole lot, in principle, could go bang.
As for the smaller masses - Jupiter, Neptune and the Moon - probably not. Especially the Moon. Fusion fuels need to be concentrated to ignite a burn, but in all three they're mixed with materials that can't sustain a fusion burn wave. Jupiter and Neptune are probably too well mixed to chemically differentiate the deuterium, while the Moon's D/He3 is present in very low concentrations.
Oh, don't get me wrong - they can't be "the" dark matter. But they're a dark matter. How significant I don't know; we'd need tighter constraints. (You're looking at a few eV from lab experiments; cosmology claims tighter bounds but take them with a pinch of salt.) So for more "physical" models that has to be taken into account. I think it's one of the signs that the problem is a lot more complicated than finding "the" dark matter -- although I know for sure that if an LSP is found people will be trumpeting that it's "the" dark matter, and then wondering why it doesn't quite fit the data, its abundance is a bit low (or high), its properties not quite right.
My only real point was that you can fit the bullet cluster with modified gravity models assuming massive neutrinos (which is a very uncontroversial assumption these days) -- the fact that that model (TeVeS) is ugly and ad-hoc and that the neutrino mass is a bit on the steep side was a bit beside the point, it's a matter of principle for me. It shows that we can't take the bullet cluster as proof that "the" dark matter is a particle. It also doesn't say that dark matter isn't a particle. Personally I strongly suspect that the dark matter problem will eventually be solved by a mixture of relativistic effects (a cylindrical metric will never be identical to Minkowski space even though the Newtonian potentials are small), poorly-applied relativity (average metrics will never evolve with the averaged metric's dynamics; and even small inhomogeneities can have a large impact on observation), some modified form of gravity (GR is wrong, we know that; what surprises me is how controversial stating that can be), standard model particles (neutrinos do have mass and are a dark matter; they're just nothing like significant enough to solve the whole problem), and some new particle species and forces between them (perhaps from SUSY or perhaps from something yet more exotic, which would be a lot more exciting).
Of course, dealing with all of that is a massive problem, and frankly if we add that many parameters into a model we'll quickly lose accuracy, because the data is nothing like good enough to constrain everything. So at the minute, unfortunately, we're more or less forced to work with phenomenology. That's fine... except when people then believe in the literal truth of a phenomenological model.
But hey, this is all just my opinion. I could very well be wrong and all of the problem is solved by an LSP. If so, so be it.
You can fly by and steal a bit of the dwarf energy.
And you need to know where they are as you will _not_ end up anywhere near Sirius if you do not...
if an H-Bomb is "tiny"
An H-bomb is tiny on a planetary scale, let alone a stellar one.
It's official. Most of you are morons.
Little defensive, are you? What part of my post did you not understand? The part where I didn't say MOND and cousins is impossible? Or the part where I said it was unlikely?
I can also fit the Bullet Cluster data by postulating my theory of warm blue cheese attraction (plus dark matter), but that doesn't make it interesting.
A modified gravity fit for the bullet cluster appears to require neutrinos with a mass of about 2 eV. Current experimental data limits neutrino mass to possible that neutrinos weigh that much, but not particularly likely. Most physicists bet around the 1 eV range.
Modified gravity theories still require an ad hoc modification of gravity, for which there really is very little justification. As you point out yourself, we already know there are dark matter particles (neutrinos) that account for some of the missing mass, and there are actual preexisting theoretical reasons to think there might be others.
So one theory requires an unjustified (and often finely tuned) modification to gravity plus dark matter, while the other requires dark matter, which we already suspected existed anyway.
Yes, I know that you're probably citing something that you saw once on Discovery Channel. That doesn't make it consensus science. q.v. 2012.et al, etc, ad nauseam
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
There's no actual evidence of a companion star. If there were a companion star there would be perturbations of planetary orbits; and there aren't.