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Researchers Discover a Star's Minimum Possible Mass

Posted by ryuzaki0 on from the must-be-this-large-to-ride dept.

paulmac84 writes "Stars that don't have enough mass never shine, dying billions of years before their bigger counterparts. But astronomers have never been able to measure the exact mass limit, because the lightest stars that do shine can be simply too faint to detect. Now, new images show for the first time how big a star must be to avoid impending doom. The long-awaited new images finally lay this question to rest, say the authors. The dimmest stars were measured as being 8.3% of the Sun's mass. All protostars that are smaller than this are headed for life as a brown dwarf."

112 comments

  1. Hmmmm... by chill · · Score: 0, Offtopic

    The first thing that popped into my mind when reading the title was Marlon Brando, but that would have been a star's maximum possible mass. Of course, there is also the ongoing Hollywood research of the maximum possible ego size, for which there seems to be no upper bound.

      Charles

    --
    Learning HOW to think is more important than learning WHAT to think.
    1. Re:Hmmmm... by Corwn+of+Amber · · Score: 2, Funny

      The highest possible ego mass for a star must be Francis Ford Coppola then ... or did it collapse under its own weight?

      --
      Making laws based on opinions that stem up from false informations leads to witch hunts.
  2. Finally a Definitive Answer! by Aidski · · Score: 3, Insightful

    ...Unless newer technology finds dimmer stars, and they have to lower the minimum again.

    1. Re:Finally a Definitive Answer! by bradkittenbrink · · Score: 1, Insightful

      I have a strange suspicion that after I go RTFA, I'll be able to come back and say RTFA!

    2. Re:Finally a Definitive Answer! by gardyloo · · Score: 3, Informative

      Cute. Though people could just go ahead and read the article. To wit:
      Although the telescope would have been able to detect fainter stars, none could be found- so it appears that they simply don't exist. "We checked the instruments over and over again" said Professor Richer "but we don't see any stars fainter than this".

    3. Re:Finally a Definitive Answer! by helioquake · · Score: 0, Redundant

      ...Unless newer technology finds dimmer stars, and they have to lower the minimum again.

      There may be some truth in this comment. Could it be 8.2% instead?

      Whenever you read an article like this, we should pay attention to the error bar. Is it 8.3% +/- 1, 5, or 50%?

    4. Re:Finally a Definitive Answer! by Lave · · Score: 3, Interesting
      Sorry to be pedantitc but FTFA:

      Although the telescope would have been able to detect fainter stars, none could be found- so it appears that they simply don't exist. "We checked the instruments over and over again" said Professor Richer "but we don't see any stars fainter than this".

      So they could have detected much dimmer stars but didn't - so assuming a big enough sample, they discovered the minimum mass to initiate fusion. Pretty impressive.

      So finally a Definitive Answer! Until someone bothers to look at a larger sample set,, finds dimmer stars, and they have to lower the minimum again.

      --
      http://skeptobot.blogspot.com/ - A site for the Renaissance man and woman
    5. Re:Finally a Definitive Answer! by cswiger2005 · · Score: 5, Informative

      If there were dimmer stars present there, the Hubble's main camera would have been sensitive enough to have seen them...they're pretty sure of this because they were able to notice some very dim white dwarfs (a white dwarf is the remenant stellar core of a bigger star which went nova; they are very hot [initally] but also very tiny), which are dimmer than the smallest M-class stars still in the main sequence.

      Basicly, this observation is in reasonably close accordance with the theories about stellar fusion; basicly, an potential star needs to have about ten or fifteen times Jupiter's mass before deuterium fusion is possible, and about 70 times Jupiter's mass before normal hydrogen fusion happens (according to the models).

      Jupiter weighs 1.899 * 10^29kg; Sol weighs 1.989 * 10^32 kg (or about 1050 times what Jupiter weighs).
      8.4% of Sol's mass is 1.65 * 10^30, or 87 times what Jupiter weighs.

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    6. Re:Finally a Definitive Answer! by Anonymous Coward · · Score: 0

      When an error figure is not given it's assumed to be +/- 1 in the least significant digit. So, anywhere from 8.2% - 8.4%.

    7. Re:Finally a Definitive Answer! by helioquake · · Score: 2, Insightful

      Photometric uncertainty with the HST/ACS could probably be as high as one percent. There is no way in this kind of astronomy that can determine the percentage good to 0.1%.

      I know what you are getting at: you are basically talking about significant figures, which isn't a bad guess. But here I am referring to more traditional statistical errors that should be propagated through analysis.

      I just read the actual paper and it doesn't have any good estimate on the error.

      Just FYI.

    8. Re:Finally a Definitive Answer! by Anonymous Coward · · Score: 0

      Twitch, twitch... it's basically

      I know, I know, spelling police and all that. Can I help it that I'm obsessive compulsive?

    9. Re:Finally a Definitive Answer! by denim · · Score: 1

      Of course they don't see stars fainter than the minimum they can see. That seems kind of circular.

      And when they say "shine", what do they mean? In what spectrum? To what brightness? Another way to ask this is, what makes a brown dwarf "brown"?

      --
      Being quick to take offense is not a virtue.
    10. Re:Finally a Definitive Answer! by jZnat · · Score: 1

      No, what they're saying is that their telescope could detect fainter stars, but it didn't find any.

      --
      'Yes, firefox is indeed greater than women. Can women block pops up for you? No. Can Firefox show you naked women? Yes.'
    11. Re:Finally a Definitive Answer! by denim · · Score: 1

      Which only proves that it didn't find any, not that such don't exist. Radiation from such could, I expect, be blocked by various other objects or phenomenon. And would probably be hard to see in the first place.

      --
      Being quick to take offense is not a virtue.
    12. Re:Finally a Definitive Answer! by 4D6963 · · Score: 1

      So finally a Definitive Answer! Until someone bothers to look at a larger sample set,, finds dimmer stars, and they have to lower the minimum again.

      I'd rather say, finally a definitive answer, period. The reason why stars cannot be smaller than that limit is theorical, and the observation allows us to find that limit. A larger sample set will not lower the minimum, ever. It will only reduce the margin of error. The dimmest star you could ever find is comprised in the margin of error we got.

      --
      You just got troll'd!
    13. Re:Finally a Definitive Answer! by qurk · · Score: 1

      I didn't mean to treat you bad Didn't know just what I had But, honey, now I do And don't it make my brown eyes Don't it make my brown eyes Don't it make my brown eyes blue

    14. Re:Finally a Definitive Answer! by Down_in_the_Park · · Score: 1

      Thanks for the numbers, that was exactly what I was asking myself, how far is Jupiter weight off from the limit. Now, what's the difference between a brown dwarf and a massive Planet? Just the way the became into existence or is every massive object close to a star considered as a planet and if it is by its own a brown dwarf?

      --
      "People who are willing to sacrifice essential freedoms for security deserve neither freedom nor security."

      B F
    15. Re:Finally a Definitive Answer! by qeveren · · Score: 1

      True, the old 'absence of proof is not proof of absence' thing almost always applies in science. But as stars go, the lower the mass, the more common they are. It's very unlikely that they'd not see at least one lower-than-this-limit star with their instruments if they were out there; there'd be enough of them that they couldn't all coincidentally be hidden.

      --
      Don't just stand there, get that other dog!
    16. Re:Finally a Definitive Answer! by denim · · Score: 1

      Agreed, which says to me that they only believe they'd be able to detect such objects, not that they actually can. That's my theory. IIRC, Jupiter puts out more energy than it gets from the Sun. Is it not smaller than their lower limit? What's the difference between an object like Jupiter and a brown dwarf or star? As I said earlier, what makes a brown dwarf "brown"? What spectrum range defines a star?

      What I'm saying is that if it puts out energy, why is it not a star? Counter proposal: is a black hole putting out energy? Is it a subset of "star"? What sort of energy need a "star" emit? How much of this energy? How often? Is a faded old white dwarf still a star? Define your terms, sirs.

      If they can define a planet to be any old rounded rock in solar orbit, I can define a star to be an object putting out more energy than it takes in.

      --
      Being quick to take offense is not a virtue.
    17. Re:Finally a Definitive Answer! by denim · · Score: 1

      BTW, can we now consider our Earth/moon system to be a double planet? The moon is a gravity-rounded rock, so by the new definition, it's a planet. What shall we call it now? That follows for all such moons in our system, such as those around Jupiter, Saturn, Neptune, and Uranus. Whew, we've got a lot of "planets" now! They really killed themselves once they declared Charon as a planet, IMHO. Opens up the field too far.

      --
      Being quick to take offense is not a virtue.
    18. Re:Finally a Definitive Answer! by AndyTheSayer · · Score: 1

      I don't think so, because the barycentre of the Earth-Moon system is inside the Earth (as opposed to, in the case of Pluto and Charon, somewhere in space between them).

    19. Re:Finally a Definitive Answer! by denim · · Score: 1

      I don't recall hearing anything in the definition about the location of center of mass, or of relative masses/sizes. Just that the new planet definition said that the body had to have become rounded through gravity. Maybe I should look for their actual statement.

      --
      Being quick to take offense is not a virtue.
    20. Re:Finally a Definitive Answer! by Squiffy · · Score: 1

      So you're arguing science without understanding it? Shame on you.

    21. Re:Finally a Definitive Answer! by denim · · Score: 1

      What am I saying I don't understand?

      --
      Being quick to take offense is not a virtue.
    22. Re:Finally a Definitive Answer! by denim · · Score: 1

      Okay, now I've seen this http://www.cnn.com/2006/TECH/space/08/18/moon.plan et/index.html article, so I see what you're talking about. I'll have to give you that one. It still leaves the question of what is a star.

      --
      Being quick to take offense is not a virtue.
    23. Re:Finally a Definitive Answer! by cswiger2005 · · Score: 1

      A planet is something which does not have enough mass to sustain a fusion reaction.

      Unless a star is nearby, planets are effectively invisible at stellar distances since they radiate no light of their own. Even with a star nearby, it's easier to notice the gravitational wobble of the planet shifting the star's orbit and causing doppler changes to the star's spectrum than to observe the planet directly via reflected light.

      A "brown dwarf", sometimes referred to as a T-class star is something that emits enough energy to be detected (ie, mainly in the red or infrared spectrum and thus must have a surface temperature of at least 800-1200 K), which means they have to have at least some energy from gravitational collapse or minimal deuterium fusion happening to generate this light, but they are smaller and cooler than the smallest "normal" star class, which is M.

      M-class stars have temperatures between 2000 - 3300K, and apparently have a mass between 0.1 and 0.6 solar masses. Note that astronomy is still integrating the information and updating the classification of stars, so they've added both the L and T classes; I gather that an L-class star is one between the T-class brown dwarfs and M-class, having a mass of ~0.01 to 0.1 solar masses, temperatures of 1200 to 2000K, and are getting enough energy from deuterium fusion to perhaps also be burning some normal hydrogren.

      Again, anything that is observed to be radiating mainly infrared and little or no higher-energy/higher-temperature bluish light is going to be a "brown dwarf" by observation, and the smaller M-class and all L & T class stars would qualify as being "brown dwarfs". I gather the difference is that the T-class stars are so small that they go out in a few millions of years (once the initial energy gained from gravitational collapse of the protostellar gas cloud the star condensed from has been radiated away and they cool down below even the deuterium fusion threshold); L-class stars will burn deuterium until they run out (hundreds of millions of years?); and the smallest M-class stars, which weigh enough to fuse normal hydrogen, will burn for trillions of years.

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    24. Re:Finally a Definitive Answer! by fatty13 · · Score: 0
      Jupiter weighs 1.899 * 10^29kg; Sol weighs 1.989 * 10^32 kg (or about 1050 times what Jupiter weighs). 8.4% of Sol's mass is 1.65 * 10^30, or 87 times what Jupiter weighs.
      So... How many monoliths is that? TMA-2, the one found in Jupiter space is said to be 1/2 a Kilometer in length, putting this into the 1x4x9 ratio, this leaves us with a monolith with dimensions of
      55.55m X 222.22m X 500m and volume of ~6.1728395e6. m^3
      The mass of TMA-2 is hard to quantify, but given it's wormhole/transformative/starchild/total wtf powers, let's assume it to be at least the mass of say... platinum? (owing to it's value and all). Platinum has a density of 21.45 g/cm^3 = 21.45e3 kg/m^3.

      So, the mass is:

      ~6.1728395e6. m^3 X 21.45e3 kg/m^3 = 1.32407407407407e11 kg.

      number of monoliths = (mass required - mass of Jupiter) / est mass of monolith =

      1.653e30 - 1.899e29 / 1.324e11 = 1.10279456e19
      So, we're left with: ~1,102,794,560,000,000,000 monoliths... Shouldn't be too hard to take care of that and turn night into day for a thousand years or so...

    25. Re:Finally a Definitive Answer! by cswiger2005 · · Score: 1
      IIRC, Jupiter puts out more energy than it gets from the Sun.

      This is possibly true, although the difference in energy being received and the observed temperatures are within a reasonable tolerance (~ 10%?); whether this is because Jupiter has some extra energy due to radioactive decay, or continued gravitational compression, or whether it's just a measurement error is not clear.

      Is it not smaller than their lower limit?

      Yes. It's not expected that Jupiter is fusing any significant amount of deuterium or normal hydrogen. To a good first approximation, the thermal radiation from Jupiter (about 200K IIRC) corresponds with the amount of energy from solar radiation it is receiving.

      What's the difference between an object like Jupiter and a brown dwarf or star? As I said earlier, what makes a brown dwarf "brown"? What spectrum range defines a star?

      Mass. A brown dwarf emits enough radiation that it is visible in IR or red light, which requires a surface temperature of anywhere from around 800K to about 2000K.

      You can figure these things out just by doing a naked-eye judgement of the color of the objects, or you can look at something called Wein's law, which relates temperature to the colors (or wavelength) of the radiation being emitted by that object:

      Wikipedia on Wein's law

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    26. Re:Finally a Definitive Answer! by denim · · Score: 1

      Good answer.

      So the definition of a star is an object which emits radiation due to fusion, or which did at one time?

      --
      Being quick to take offense is not a virtue.
    27. Re:Finally a Definitive Answer! by cswiger2005 · · Score: 1

      Yeah, that's about it.

      If the object isn't heavy enough to undergo fusion by itself, it's not considered to be a true star...but objects which were heavy enough to be a star, and then went into the red supergiant phase or go nova, the left-over stellar core (a "white dwarf" or "neutron star", respectively) will still be considered a star until they cool below 1000K or so.

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    28. Re:Finally a Definitive Answer! by Squiffy · · Score: 1

      What's the difference between an object like Jupiter and a brown dwarf or star? As I said earlier, what makes a brown dwarf "brown"? What spectrum range defines a star? What I'm saying is that if it puts out energy, why is it not a star? Counter proposal: is a black hole putting out energy? Is it a subset of "star"? What sort of energy need a "star" emit? How much of this energy? How often? Is a faded old white dwarf still a star? Define your terms, sirs.

      These are things you don't understand, by your own admission. You say, "Define your terms, sirs," as if people were failing to clarify what they mean. But the onus was actually on you, because any layman's text on astronomy will clearly describe, for example, the difference between a brown dwarf and a star.

      Your ignorance wasn't what bothered me: no one knows everything. It just irks me when I see someone with a confident but uninformed opinion.

      It looks like someone else has already answered your questions, so I'll end here.

    29. Re:Finally a Definitive Answer! by DeanAsh · · Score: 1

      Sol's mass is 1.98892 × 10^30 kilograms, not 10^32 (courtesy of Google). Likewise, Jupiter masses 1.8987 × 10^27 kilograms (not 10^29)

      --
      What is the shortest sig that cannot be expressed in fewer than 20 words?
  3. Um... yay? by Capt'n+Hector · · Score: 3, Interesting

    This is a simple math/physics problem. I'm not quite sure what the grand point of it is though (kinda like the pluto(!)=planet debate). Maybe you can graph the distribution of star masses, and then see how much "dark matter" there is on the tail end of brown dwarfs.

    --
    Quid festinatio swallonis est aetherfuga inonusti?
    Africus aut Europaeus?
    1. Re:Um... yay? by Anonymous Coward · · Score: 0

      Yes it is just a math/physics problem, but it is by no means simple. Sure, if you make a number of simplifying assumptions about convection in a star, you could get an undergrad astrophysics class to tell you the minimum mass of a star. But in reality, the processes that drive convection in a star are incredibly complex, and not entirely understood.

    2. Re:Um... yay? by ZorbaTHut · · Score: 4, Insightful

      Many years ago people believed that heavy things fell faster than light things. They didn't bother testing this theory because they knew it to be true. Then, one day, someone tested that theory and found it was false.

      Perhaps it is a simple problem to answer mathematically. And now we've tested it. We have actual data. Does the data match up with the mathematical answer? Maybe, maybe not, I don't pretend to know. But I imagine people out there do - so either we've got another point of verification that our models are good, or it's time to figure out what's wrong with them.

      Either way, this is what's called Science.

      --
      Breaking Into the Industry - A development log about starting a game studio.
    3. Re:Um... yay? by Artifakt · · Score: 3, Interesting

      It's not quite simple. It's admittedly very simple in the abstract, for a model star where you're only looking at what combinations of temperature and core density allow standard stellar fusion at a break even rate (All normal stars run at break even, in the short enough run, in the sense that the total energy produced is equal to the light pressure keeping interior layers from collapsing, plus the light emmitted to space). Physicists such as Hoyle and Gamow pretty much wrote the math for this at least forty years ago, and much of this was known well before the US designed the "Super" in 1949-50, where it turned out to be applicable (although some of it was so classified then that even the best professional Astrophysicists couldn't assume they had seen nearly all the relevant literature).

              Here's just some of what makes it more complex for the real world though, and I'm probably missing plenty of other complexifying factors:
              Spinning Star? What range of rotation rates occurs in low-mass stars, How much pressure does it relieve at the core at a minimum? (Is there any real occurance of a low mass star with absolutely no rotation?)
              Which Population (I or II). Low mass stars can be very old, as they burn their fuel so slowly. This affects how much of the heavier elements are found in their cores. Just where newer generation stars formed makes a big difference in how much of what heavier elements are in them, but there's not much of a difference theoretically possible for the first generation. Are their faint stars can we observe, but not get enough of a spectrum on to be confident of their composition?
                Are there any convection currents in low mass stars? Do such, as yet unproved, currents include the full range of modalities found in a star the size of our Sun, or fewer? (or maybe even something truly novel, completely different than in bigger stars?). We're not even real sure how typical current patterns within our Sun are for stars of its general type, last I looked.
                Can having a large, close companion star significantly reduce the minimum mass threshold, or would any such received radiation effects be trivial?

      --
      Who is John Cabal?
    4. Re:Um... yay? by munpfazy · · Score: 4, Informative
      Yes it is just a math/physics problem, but it is by no means simple. Sure, if you make a number of simplifying assumptions about convection in a star, you could get an undergrad astrophysics class to tell you the minimum mass of a star. But in reality, the processes that drive convection in a star are incredibly complex, and not entirely understood.


      True enough, but both back-of-the-envelope calculations and the best models give you an answer that's spot on, to within something less than a factor of two. It's not as though there's some great debate within the community about whether the minimum mass for pop-II stars is significantly different from .08 M_sun.

      I'm a great fan of observational confirmations, and of giving Hubble time to people doing this sort of work, but it's hard to imagine why anyone who isn't a specialist in stellar modeling looking to test their code to within a few percent would care about this particular result.

      It hardly seems like press release material. What's more, dressing up the article to make it seem like some great mystery has been solved is disingenuous.

      But, I suppose, "this just in: astronomers have confirmed something that they've been rather confident is true for decades" doesn't sell papers.
    5. Re:Um... yay? by helioquake · · Score: 2, Informative

      I'd add chemical composition (metallicity, namely), too, to your list.

    6. Re:Um... yay? by helioquake · · Score: 1

      Ooops sorry, it's already in there.

    7. Re:Um... yay? by rthille · · Score: 1

      Now that's crazy talk. Everyone knows that the most important knowledge is passed down from generation to generation in a verbal tradition or a book that's (mis)copied by scribes. There's no need for 'fact checking'. Jeeze, kids these days...

      --
      Awesome furniture, accessories and cabinetry in Santa Rosa, CA: http://humanity-home.com/
    8. Re:Um... yay? by G-funk · · Score: 1

      I've never seen any mathematical proof that heavy things don't fall faster than light things. F=Gm/d^2.

      --
      Send lawyers, guns, and money!
    9. Re:Um... yay? by ars · · Score: 1

      "Many years ago people believed that heavy things fell faster than light things. They didn't bother testing this theory because they knew it to be true. Then, one day, someone tested that theory and found it was false."

      Bit of a problem in your argument there - heavy thing DO fall faster then light things!

      It's just that on earth, the earth is so much larger then the falling item, that if the faller is a little bigger or a little smaller it's not much noticable.

      OTOH if you get some nice large objects - say the moon vs an asteroid falling on earth, the moon will fall faster. (Well technically the earth will fall up to the moon, but from the POV of the earth the moon is falling faster then the asteroid.)

      But even with small objects on earth, heavy things do fall faster. (But good luck measuring the difference.)

      --
      -Ariel
    10. Re:Um... yay? by meringuoid · · Score: 1
      Spinning Star? What range of rotation rates occurs in low-mass stars, How much pressure does it relieve at the core at a minimum? (Is there any real occurance of a low mass star with absolutely no rotation?)

      The rotation of a star would presumably be a result of its original collapse. Conservation of angular momentum. Hence the really enormously fast rotation of extremely collapsed objects like pulsars.

      A low-mass star, then, would probably spin relatively slowly. Less mass means less angular momentum. Since we're looking at protostars, they wouldn't have had time to exchange angular momentum with other systems, so I wouldn't expect to find any that weren't rotating at all either.

      --
      Real Daleks don't climb stairs - they level the building.
    11. Re:Um... yay? by AndyTheSayer · · Score: 1

      But to work out speed from that you then have to consider F = ma, so when you work out acceleration the mass cancels out (i.e. acceleration is independent of mass). Since s = ut + 0.5a(t^2), this gives a speed also independent of mass.
      Note that there's a lot of other factors such as air resistance which are important too, though.

    12. Re:Um... yay? by cswiger2005 · · Score: 1
      Bit of a problem in your argument there - heavy thing DO fall faster then light things!

      Actually, if you go to a decent science museum, they should have an exhibit where they show something like a feather and lead shot being dropped in a vaccuum...really and truely, they fall at exactly the same speed and hit the ground at the same time.

      If you plug in F=M1a and F = gM1M2/r^2, you discover that the gravitational attaction of a heavier object to the earth exactly counterbalances the weight of the heavier object, so all objects experience the same acceleration due to the earth's gravity (M1a = gM1M2/r^2 => a = gM2/r^2, or a ~= 9.8m/s, where M1 is the mass of the test object, M2 is the earth's mass, r is the radius of the earth).

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    13. Re:Um... yay? by ars · · Score: 1

      "Actually, if you go to a decent science museum, they should have an exhibit where they show something like a feather and lead shot being dropped in a vaccuum...really and truely, they fall at exactly the same speed and hit the ground at the same time."

      No, not "really and truely", only "approximately". I guess you missed where I wrote the difference on earth is not noticable. But just because you can't see it doesn't mean it's not there.

      You have an error in your equation: you forgot about the acceleration of the EARTH toward the test object! Your equation is only half of what actually happens. When you drop an item on earth, the object falls toward the earth - but at the same time the earth moves 'up' toward the object. The heavier the object the faster the earth moves up.

      Now just because the earth is really big, and moves so little, doesn't mean it doesn't move. It does, it has to, you just can't see it.

      And while on the subject of equations that are only approximately true there is the well known thing about pendelums always swinging at the same time period regardless of the angle or mass. Also true only to an approximation. In reality the time period DOES depend on the angle (and the mass), just not by much.

      See you need to distinguish between stuff that is emperically 100% correct, and stuff that is USEFULLY correct.

      I'm perfectly happy using equations for falling, or pendlums that are only approximately true. They are close enough. But it's equally important to know when they are NOT close enough. Partial knowledge is not a good thing.

      --
      -Ariel
    14. Re:Um... yay? by cswiger2005 · · Score: 1
      You have an error in your equation: you forgot about the acceleration of the EARTH toward the test object!

      No, actually, I haven't.

      Notice that both objects are being released at the same time; the motion of the Earth towards them is not different for one object versus the other, presuming it was significant at all (which it is not; the Earth weighs about 10^26 times what a 5kg lead pellet weighs). When you drop two objects from the same height, at the same time, in a vaccuum, they will hit the ground at exactly the same time.

      See you need to distinguish between stuff that is emperically 100% correct, and stuff that is USEFULLY correct.

      And for your next trick, will you acknowledge the difference between being correct, being wrong, and being an obnoxious pedantic git?

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    15. Re:Um... yay? by ars · · Score: 1

      "Notice that both objects are being released at the same time; the motion of the Earth towards them is not different for one object versus the other"

      You seem to have forgotten we are talking about how fast objects fall, not comparing them. Go back and read the post that started this.

      "presuming it was significant at all (which it is not; the Earth weighs about 10^26 times what a 5kg lead pellet weighs)."

      WOW! you don't say, I have never heard of this before, the earth is heavy? The fact I said this at least 3 times already didn't clue you in?

      "When you drop two objects from the same height, at the same time, in a vaccuum, they will hit the ground at exactly the same time."

      And if I tie two objects together and drop them, they will also hit the ground at the same time. Please don't act stupid. Just because in your specific setup you made them hit the ground at the same time, does not mean that heavy and light objects fall at the same speed (relative to whatever they are falling toward).

      "And for your next trick, will you acknowledge the difference between being correct, being wrong, and being an obnoxious pedantic git?"

      So I guess you live by truthiness. Someone wanting to be correct is automatically "obnoxious pedantic git", that's nice, enjoy living in a world where it's more important not to rock the boat, never mind what's really happening.

      PS. Little tip when arguing: the guy who starts with the name calling usually has the weaker position (see ad hominem).

      --
      -Ariel
    16. Re:Um... yay? by cswiger2005 · · Score: 1
      You seem to have forgotten we are talking about how fast objects fall, not comparing them.

      How do you measure velocity, eh? Measure the distance, divide by the elapsed time?

      Well, in the specific example I gave, and in the historic example involving a leaning tower in Italy, the distance and the time are exactly the same for the two objects...so the the velocity ("how fast"), is also the same.

      Go back and read the post that started this.

      The post by ZorbaTHut, hmm? Modded +5 because it had a good point, which you followed up by a needlessly pedantic correction which isn't actually even true for these specific circumstances? All this guff about "truthiness" is just an attempt to change the subject from matters of fact (which can be, and have been tested in real-world circumstances), to avoid admitting your mistake.

      Don't blame me for being wrong...you've managed that all by yourself.

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    17. Re:Um... yay? by Teancum · · Score: 1

      While I think this whole thread is utter BS, I would point out that when you drop a much more dense object (generally considered "heavy") compared to a substantially less dense object like a feather in an atmosphere, the heavier and more dense object usually drops much faster. Visibly so.

      Or the thing to point out is that atmospheric drag is a big deal. As for the miniscule amount that a slightly more massive object would have on gravitaional attraction, it isn't worth worrying about. And if you do the math using Newton's equations, any difference disappears. Dropping Jupiter onto the surface of the Earth falls just as fast as dropping a proton. Seriously. Do the math to prove it.

    18. Re:Um... yay? by cswiger2005 · · Score: 1
      I would point out that when you drop a much more dense object (generally considered "heavy") compared to a substantially less dense object like a feather in an atmosphere, the heavier and more dense object usually drops much faster. Visibly so.

      Of course-- that is so intuitively true that nobody [1] questioned it for the 2000-odd years between Aristotle & Gallileo.

      On the other hand, you can take two pieces of paper, which weigh the same, and have the same density, and crumple one into a tight ball, and discover that they also fall at different speeds-- which means your experiment isn't measuring just one thing, but is being strongly influenced by the friction from air resistance.

      And that's the point of scientific reasoning and experimentation-- to recognize that measurements are imprecise and can be biased due to a number of factors [2], sometimes so much that they prevent you from making truthful conclusions about what is actually going on. And that's why clever ways of conducting an experiment so that you can eliminate these biases, or by making a relative comparison where the bias cancels itself out leaving a more meaningful result, are so important and valuable to understand.

      Dropping Jupiter onto the surface of the Earth falls just as fast as dropping a proton.

      Surely that should be the other way 'round? :-) The Earth is about the size of Jupiter's Red Spot, and would disappear inside Jupiter's atmosphere without making much difference as far as Jupiter was concerned...

      [1]: Well, almost nobody. The all-knowing Oracle of Wikipedia mentions John Philoponus and Giambattista Benedetti.
      [2]: Not the least of which is human nature. See the .sig below.

      --
      "The human race's favorite method for being in control of the facts is to ignore them." -Celia Green
    19. Re:Um... yay? by Teancum · · Score: 1

      OK, think more like a black hole with Jupiter's mass. The point I'm trying to make is that the mass of the object is immaterial.

      This BTW is a serious problem with other scientific investigations, where some "theories" are offered, but realisticly eliminating extra factors that influence the results is often difficult or impossible to do. The whole issue of global warming, for instance, has so many variables that the one often used conclusion, that human-caused pollution is directly causing global warming and that CO2 production by mankind specifically is the cause, is such a small piece of the overall picture that I don't believe those "researchers" are getting it right. That is but one of litterally hundreds of variables that can influence the overall global temperature.

      BTW, this isn't arguging that the temperature of the world isn't going up, which is plainly obvious. The causes of it are what I strongly question, and many factors simply aren't taken into account or are wrongly trivialized. What happens with global warming research is more of a religion rather than a serious scientific inquiry, which is why it always sparks huge debates among participants. When these scientists say we must spend trillions of dollars to do things according to their political agenda exactly as they proclaim, I really start to wonder exactly what their agenda is all about. And yes, for some of the more extreme proposals, it would be trillions of dollars to fix the world according to their viewpoint, with massive relocations of individuals and substantial changes in how human society works. Or mass genocide of historic proportions that make the Jewish Holocaust seem like a minor criminal execution. Such proposals are thus unrealistic and will never happen.

      In the case of trying to determine the relationship between mass and gravity, the number of variables is significantly less, which is why Newton suddenly realized and calculated that the gravity of the Earth on the Moon was identical to that of the gravity of the Earth on an Apple, or any other falling object. In fact, he demonstrated and calculated the speed of the moon in a circular orbit and what tangential velocity it would need if it was fighting gravity, and what that speed was in terms of observations. Those numbers turned out to be identical within a margin of error and gave support to Newton's theories.

      This was one of the very first concepts that could be scientifically documented as working in places off of the Earth. That knowledge of the universal gravity constant "G" is known to such a pathetically few number of significant digits is one of the current travesties of modern physics.

    20. Re:Um... yay? by G-funk · · Score: 1

      Then why do you bounce around on the moon?

      --
      Send lawyers, guns, and money!
  4. 8.3%? by Anonymous Coward · · Score: 2, Funny

    Apparently, size does matter

  5. For those who are wondering... by Anonymous Coward · · Score: 5, Informative

    ... that's 87 Jupiters.

    1. Re:For those who are wondering... by i_should_be_working · · Score: 1

      +1. That's the first thing that came to my mind. So I guess the events of 2010 can't happen then. Punk ass Jupiter, thinks it's tough.

    2. Re:For those who are wondering... by Anonymous Coward · · Score: 3, Interesting

      I believe that 2010 should still be feasable. It's been a few years, but as I recall it the monoliths descended into Jupiter and used some exotic forces to compact it down to a scale where it was finally dense enough to ignite fusion. This article only speaks to how massive something must be for gravity to compact it that far; theoretically all you really need for a self-sustaining reaction is the proper density and pressure, however those might be achieved.

    3. Re:For those who are wondering... by Null+Nihils · · Score: 3, Funny

      How much is that in Libraries of Congress?

    4. Re:For those who are wondering... by DragonWriter · · Score: 1

      Yeah, but its not a one-time thing, you have to maintain it. So those mystical monoliths would have to hang out and continue exerting their magical force to make it work.

    5. Re:For those who are wondering... by tgd · · Score: 3, Insightful

      Silly, a LoC is a unit of informational quantity, not mass.

      What we really need to know is how many clown-laden Bugs is that?

    6. Re:For those who are wondering... by JDevers · · Score: 1

      Well, you have to remember that the obelisks are what caused that to happen. There is nothing explaining that they aren't 95% of the mass of the new sun and jupiter just provides the hydrogen (which would probably last plenty long enough to do what was needed on Europa).

      Plus, it was just a book =)

    7. Re:For those who are wondering... by RsG · · Score: 1
      What we really need to know is how many clown-laden Bugs is that?
      Depends on the mass per clown, now doesn't it? Also, are we using metric or imperial clowns?
      --
      Erotic is when you use a feather. Exotic is when you use the whole chicken.
    8. Re:For those who are wondering... by tgd · · Score: 1

      Jeez, maybe NASA can help us with this.

    9. Re:For those who are wondering... by Blnky · · Score: 1

      I thought about that too and realized it is still possible. The monoliths can maintain the reaction. After all, for each monolith, "...it's full of stars!" :P

    10. Re:For those who are wondering... by Dachannien · · Score: 3, Insightful

      Silly, a LoC is a unit of informational quantity, not mass.

      Holy crap, you mean the Library of Congress is massless?!

    11. Re:For those who are wondering... by doshell · · Score: 1

      I'm not really sure how to express it in LoC, but knowing that Burning Library of Congress (BLoC) is roughly 4 petajoules and also that E = mc^2,

      E = 0.83 * solar mass * c^2 = 1.48e47 J = 1.48e32 PJ = 3.7e31 BLoC

      which allows us to truly appreciate the order of magnitude in question.

      --
      Score: i, Imaginary
    12. Re:For those who are wondering... by EMH_Mark3 · · Score: 1

      It has to be: the whole separation of church and state thing, you see.

      --
      Burn the land and boil the sea, you can't take the sky from me
    13. Re:For those who are wondering... by MindStalker · · Score: 1

      Mentioning that, can anyone explain to me whats the difference between the large gaseus planets like jupiter and small stars. Is there really any difference in their compesition or is it simply a matter of size?

    14. Re:For those who are wondering... by ceoyoyo · · Score: 1

      No you don't. If you took some portion of Jupiter's mass and turned it into neutron star stuff then fusion could occur in the rest of the regular gas. The trick is to get the pressure up, it doesn't matter how. You can do it with a certain mass of regular matter or you can use a bit of stable exotic matter with the regular matter packed around it.

    15. Re:For those who are wondering... by syntaxglitch · · Score: 2, Informative

      Mostly size, or rather, mass. If you dumped enough hydrogen into Jupiter, it would shine. You just need enough gravitational pressure at the core to sustain hydrogen fusion, which is what the article is discussing.

      That said, relative composition IS different; Jupiter has a dense rocky core of heavier elements (the same sort of stuff the inner planets are made of), surrounded by metallic, liquid, and gaseous hydrogen and some helium. The sun is almost completely made of hydrogen and helium, with a reside of heavier elements, and various layers distinguished mostly by density, temperature, and various physical properties (for instance, the 'photosphere' is the layer at which hydrogen ions render the sun's atmosphere opaque to visible light, and hence is the visible 'surface' of the sun.).

    16. Re:For those who are wondering... by Amazing+Quantum+Man · · Score: 1

      You're off by a factor of 10. It was 8.3%, or 0.083 solar masses.

      --
      Fascism starts when the efficiency of the government becomes more important than the rights of the people.
    17. Re:For those who are wondering... by Anonymous Coward · · Score: 0
      Your mom was off by a factor of 10 last night!

      Uh... 1. Nazis! 2. ??? 3. Profit! portmangrits blaljsd8s9udyfsauiodfhjasdkf;sd TUBGIRL snsodfoskd

    18. Re:For those who are wondering... by shemnon · · Score: 1

      Try as I might, I cannot get google to tell me how many black monoliths are needed to make Jupiter 87 times more massive than it is...

      --
      --Shemnon
    19. Re:For those who are wondering... by Anonymous Coward · · Score: 0

      "I must have put a decimal point in the wrong place or something.
      Shit. I always do that. I always mess up some mundane detail."

    20. Re:For those who are wondering... by master_p · · Score: 1

      easy...: 87 x libraries of Congress for Jupiter.

    21. Re:For those who are wondering... by StrawberryFrog · · Score: 1

      Holy crap, you mean the Library of Congress is massless?!

      No, just that it's not of fixed mass. You can put several books on a DVD, and the DVD weighs less. Or you could put them on stone tablets instead if tha's your thing.

      --

      My Karma: ran over your Dogma
      StrawberryFrog

    22. Re:For those who are wondering... by Bob+of+Dole · · Score: 1

      I seem to remember that the monoliths weren't making it bigger*, but denser. The idea being that Jupiter isn't a star because it doesn't have the neccesary internal pressure to initiate fusion. Instead of making it big enough that its own gravity would bring the pressure to the needed level, they just squished it. (Of course, the question then is what happens when they stop squishing it?)

      * That wouldn't be a great idea, since they were trying to help Europa's life. I bet 87 times bigger would be big enough for Europa to be within it.

      --
      I respond to your sigs
    23. Re:For those who are wondering... by qeveren · · Score: 1

      First, neutron star material is NOT stable outside of the conditions of a neutron star. You can't 'take a small piece of it'... that piece would just explode, excessively violently, if it were unconstrained. Second, fusion at the surface of neutron degenerate matter takes place at an enormous rate due to gravitational compression (we're talking an escape velocity of half the speed of light at the surface). Jupiter'd likely just get disrupted, not continue to burn, star-like.

      --
      Don't just stand there, get that other dog!
    24. Re:For those who are wondering... by Hyram+Graff · · Score: 1

      Holy crap, you mean the Library of Congress is massless?!

      Now if we could just make it spherical ...

      --
      0*0
      00*
      ***
    25. Re:For those who are wondering... by ceoyoyo · · Score: 1

      True. I don't know what the minimum sustainable mass for a neutron star is, but remember, there won't be a few pounds of it floating around in space, it'll be in the core of Jupiter and there would be a decent ball of it.

      In the book I believe Clarke just said "heavier elements." The monoliths were sucking up Jupiter's high clouds and turning the material into heavy elements, which would have the same effect, you'd just need more of it.

      Whether it would work for the millions of years mentioned in the book, I don't know. It IS just a book.

    26. Re:For those who are wondering... by collectivescott · · Score: 1

      That's not true, the Library of Congress does have a mass. It has dimensions as well. Therefore, LoC can properly be used as a unit of measurement for mass, size, or informational content. Just as soon as someone estimates its weight accurately, that is.

  6. So, is that ... by darkonc · · Score: 0, Offtopic

    bigger or smaller than Rosanne Bar?

    --
    Sometimes boldness is in fashion. Sometimes only the brave will be bold.
    1. Re:So, is that ... by helioquake · · Score: 1

      In astronomy, they are indistinguishable.

  7. I thought we knew that decades ago. by Biff+Stu · · Score: 4, Funny

    Didn't Karen Carpenter set the standard for the minimum mass of a star?

    1. Re:I thought we knew that decades ago. by kimvette · · Score: 2, Funny

      No, she went below the minimum mass for a star.

      --
      The Christian Right is Neither (Christian nor right). See: Matthew 23, Matthew 25, Ezekiel 16:48-50
  8. Simple? by Anonymous Coward · · Score: 0

    Go on then, lets see you do it...

  9. So what? by FlyByPC · · Score: 2, Funny

    In Hollywood, the minimum mass of stars has been on the decline for decades now...

    --
    Paleotechnologist and connoisseur of pretty shiny things.
  10. Brown Dwarf? by JanneM · · Score: 4, Funny

    Brown Dwarf? That's "colored star of alternaive height" to you, mister!

    --
    Trust the Computer. The Computer is your friend.
    1. Re:Brown Dwarf? by nacturation · · Score: 2, Funny

      Mister? It's person, you insensitive clod!

      --
      Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
  11. To the Astrophysicists out there by Anonymous Coward · · Score: 0

    Would this fit the definition of a standard candle? It sounds pretty useful to me if it does, though it would only be useful in this galaxy.

    1. Re:To the Astrophysicists out there by khallow · · Score: 2, Informative

      Not really. You can't nail down the mass threshhold that well without a huge statistical sample. And even if you could, the luminosity of the star probably would vary a lot around it (ie, it might change a lot if you added or lost a bit of mass). Then there's the matter of rotation. A high rotation rate probably would increase the mass threshhold for fusion. And the luminosity probably changes over time, certainly the mass balance does as the stellar wind blows mass away. Finally, you need some way to calibrate instruments in your lab using this standard. I doubt anyone has a star that they can use as a standard in their lab. Not even the fancy scientists that get to play with the black holes at the center of galaxies!

    2. Re:To the Astrophysicists out there by qeveren · · Score: 1

      Not to mention a standard candle that is challenging to resolve with your best instruments at relatively close range isn't much good for measuring distances. :)

      --
      Don't just stand there, get that other dog!
  12. We've know the answer for a while ... by WrongSizeGlass · · Score: 1
    Researchers Discover a Star's Minimum Possible Mass
    You want the minimum mass for a star? Just weigh Calista Flockhart.
  13. Orson Welles by tverbeek · · Score: 2, Funny

    So apparently Orson Welles - even at his heaviest - was still too "lightweight" to be a real star.

    Ironic.

    --
    http://alternatives.rzero.com/
    1. Re:Orson Welles by Anonymous Coward · · Score: 0

      Tom Cruise is very dim. Does that mean he is heavier than Orson Wells?

      Many paradox face we do with this.

    2. Re:Orson Welles by Anonymous Coward · · Score: 0

      What about Elvis?

    3. Re:Orson Welles by Anonymous Coward · · Score: 0

      Fat Elvis was never in Fat Orson's league.

  14. Brown Dwarfs by some+guy+I+know · · Score: 2, Funny
    what makes a brown dwarf "brown"?
    Two possible reasons:
    1. It's scared shitless of larger stars.
    2. Suntan lotion.
    Also, the politically-correct term for them is "dwarves of color", er, "short stars of color", uh, "stars of color of diminutive ...", ah, ah, "vertically challenged stars of color".
    Yeah, that's it, "vertically challenged stars of color".
    --
    Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
    1. Re:Brown Dwarfs by denim · · Score: 1

      Can "dwarves of color" be tossed?

      --
      Being quick to take offense is not a virtue.
    2. Re:Brown Dwarfs by skam240 · · Score: 1

      Everyone will have to forgive me because this is completely off topic but this is really annoying the piss out of me.

      Your signature The "USAPATRIOT" Act has nothing to do with patriotism, so I pronounce it "the you sap at riot act" to avoid confusion. literally makes absolutely no sense and is annoying. While I am certainly not a fan of the PATRIOT act suggesting that its acronym means or should read something completely unintelligible is neither funny or interesting.

      --
      I ignore Anonymous Coward posts. If you want to discuss something, that's awesome. Log in.
    3. Re:Brown Dwarfs by some+guy+I+know · · Score: 1
      Your signature The "USAPATRIOT" Act has nothing to do with patriotism, so I pronounce it "the you sap at riot act" to avoid confusion. literally makes absolutely no sense and is annoying.
      Just like the USAPATRIOT Act, which makes no sense (for its purported purpose -- stopping terrorism), and is annoying to people who value their freedom.
      The problem is that pronouncing it "the patriot act" or "the you ess eh (Canadian pronunciation of "eh") patriot act" lends it an air of legitimacy, like it's actually a patriotic law passed by patriots doing their patriotic duty.
      It's more accurate to pronounce it as a series of nonsense words, because that more accurately reflects what the Act actually is.
      However, since you find it annoying, I'll change my signature to something less controversal, at least for a while.
      Happy?
      --
      Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
  15. For a little perspective... by damburger · · Score: 2, Interesting

    8% of the Suns mass is still about 100 times the mass of Jupiter. So all that crap about turning Jupiter into a star in "2010" was a load of bollocks. Like, well, pretty much everything in that shite film.

    --
    If we can put a man on the moon, why can't we shoot people for Apollo-related non-sequiturs?
    1. Re:For a little perspective... by Anonymous Coward · · Score: 0

      FWIW, the 2010 book addresses your criticism, as the scientists on the Leonov debate how the monolith could have accomplished the conversion, given the mass requirements. The unstated answer (and apparently a theme for Arthur Clarke) is that the technology involved is too advanced (appears to be magic).

      As a side note, astronomers figure that planets can only get about 3 times the physical size of Jupiter before hitting a limit. After that, they just get heavier without getting larger due to gravity. Only the pressure of fusion allows single objects to pass that size limit.

    2. Re:For a little perspective... by cr0sh · · Score: 1

      If I remember the movie correctly (I don't remember how closely it follows the book), didn't a bunch (like a large cloud encircling the planer) of monoliths descend into Jupiter's atmosphere before it turned into a star? If so, the mass to cause that to occur came from the monoliths. Since we don't know what the mass of a monolith is, it could be quite large...

      --
      Reason is the Path to God - Anon
  16. if mama cass had shared the ham sandwich with her by Anonymous Coward · · Score: 0

    they'd both be alive today.

  17. approach to the main sequence by inertialFrame · · Score: 0

    The comments that I read here on Slashdot have mentioned many interesting things, most especially the agreement between the observed minimum mass and the predicted minimum mass, around 70 M_Jupiter.

    What seems missing from the discussion, however, though perhaps I just missed it, is any mention of what it means to claim that there is a mass below which fusion of some sort doesn't occur. Surely there is fusion at some undetectable level even in Jupiter. The question is whether the rate of fusion is high enough to have an observable effect. What would be an observable effect? That is the question that I should like to have answered.

    According to the theory of star formation, a protostar approaches the main sequence along the Hayashi track in the HR diagram. Contraction releases gravitational potential energy during this phase, and, for a low-mass protostar, the surface temperature remains roughly constant while the luminosity decreases due to the shrinking size of the photosphere. Eventually, the temperature and pressure in the core become high enough so that fusion halts the gravitational contraction. At this point, the surface temperature and luminosity stabilize, and we have a "zero-age" main sequence star.

    If for a protostar with sufficiently low mass the gravitational collapse is such that the pressure and temperature at the core increase only slowly toward an asymptotic value, and if at every time during the contraction the rate of fusion is insufficient to halt the contraction, then what would otherwise be a tight main sequence at this point on the HR diagram would end up being a wide distribution because no long-term, stable condition (such as that provided by core fusion) would constrain a large population to a narrow band in temperature-luminosity space for a long time (billions of years).

    It would be interesting to have a large enough sample to see past the low end of the main sequence. The article suggests only that the observers saw the bottom of the main sequence, but there should be brown dwarfs below it, and further tests of the theory would compare the observed distribution just below the bottom of the main sequence with predicted distributions. Such a comparison might even be useful for constraining the initial mass function of the distribution.

    1. Re:approach to the main sequence by exp(pi*sqrt(163)) · · Score: 1
      Surely there is fusion at some undetectable level even in Jupiter.
      The conditions in Jupiter are probably a long way from those suitable from nuclear fusion.
      --
      Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
    2. Re:approach to the main sequence by inertialFrame · · Score: 0

      I am well aware that the density and temperature at the core of Jupiter are a long way from those suitable for detectable nuclear fusion. Detectable, that is, by looking at Jupiter's surface temperature.

      However, even in the conditions of Jupiter's core, the cross-section for various fusion reactions is not zero. It's just really, really small. Given the large number of particles in Jupiter's core, though, it is likely that fusion is nevertheless going on at some undetectable rate.

      The point is that saying, "Fusion doesn't happen below a certain mass," is not right.

      Better would be to say that the diminishing effect of nuclear fusion, below a certain mass of object, is no longer able to stabilize the size and temperature of an object.

    3. Re:approach to the main sequence by exp(pi*sqrt(163)) · · Score: 1
      However, even in the conditions of Jupiter's core, the cross-section for various fusion reactions is not zero. It's just really, really small.
      That's kinda meaningless. I'm sure that from time to time nuclei in my immediate vicinity decide to tunnel close enough for fusion. But once something's that small, you simply ignore it.
      Better would be to say that the diminishing effect of nuclear fusion, below a certain mass of object, is no longer able to stabilize the size and temperature of an object.
      Hmmm...I thought that's what they were saying.
      --
      Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
    4. Re:approach to the main sequence by inertialFrame · · Score: 0
      Hmmm...I thought that's what they were saying.
      I must have missed it.
  18. Model stars by Roadkills-R-Us · · Score: 1

    It's not quite simple. It's admittedly very simple in the abstract, for a model star...

    I bought a model star once. Probably a Revell kit. It was quite simple. Too simple. Two halves of a ball, with a page of assmbly instructions, three pages of instructions on the proper use of model glue, two pages of instructions on the proper application of model paint, and seven pages of disclaimers. All in 8 languages.

    I filled it with hydrogen and detonated it. Made a really nice star for a few milliseconds...

  19. AstroPhysics, not Taxonomy by billstewart · · Score: 1
    The Planets-vs-Plutons argument is really about taxonomy - how to label things, and how people feel about them. The reason that the precise definition of a planet's size matters is that if you set the bar too high, then Pluto is no longer called a planet, and everybody who grew up learning that we had 9 planets gets told we only have 8 and gets really grumpy, but if you set the bar too low, not only does Pluto get bumped to being Planet 10 (because Ceres got promoted), but there's about 50 other things which is too many to teach elementary school kids the names of, and everybody gets grumpy, and on the other hand, if you get to add Xena as Planet 10 (or 12), everybody thinks that's cool. It doesn't tell you anything you didn't know about the planets we know, or let you predict anything useful about new planets we might find.

    But this new work actually tells you something about the physics of the star - if it's bigger than X% of the Sun's mass, it'll catch fire in a fusion reaction and be a real star, while if it's smaller than that, it'll wimp out. So if you're looking for new stars, you'll know better what to look for, and if you're looking at a gas cloud you can predict whether it might turn into a star in the next 100 million years.

    Where are we going? Planet 10! When? Real Soon!

    --

    Bill Stewart
    New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks