Igniting Jupiter

[damienpaul]

Hello again folks,

Ok, this is inspired from watching 2010 the year we make contact...what would it take to ignite jupiter?

[VanderL]

Oxygen and a match!

[Nuradnan]

The Jupiter' s mass is so great. Isn' t it enough to start nuclear fusion reaction? If not, how much more kilograms we need to make a star called Jupiter?

[antoniseb]

Originally posted by Nuradnan@Mar 20 2004, 01:09 PM
The Jupiter' s mass is so great. Isn' t it enough to start nuclear fusion reaction? If not, how much more kilograms we need to make a star called Jupiter?

Current Theories say that it would take about 75 times the mass of Jupiter to briefly start fusion that would consume the Lithium, and then it would stop again. at about 85 times the mass of Jupiter, you'd get a minimal red dwarf.

It will take far more mass than all the other planets and debris in the solar system [aside from the sun] combined.

[damienpaul]

ok, one can conclude there is very little chance in hell of it occurring...unless we import debris from othr systems, which i imagine is ever so slightly 'off the cards'....:wacko:

[antoniseb]

Originally posted by damienpaul@Mar 20 2004, 09:54 AM
Ok, this is inspired from watching 2010

It is a credit to Arthur C. Clarke that so much of what he wrote proved scientifically valid that we take him as accurate in other things. When he wrote the thing about Jupiter being just short of a star, we didn't actually know.

Likewise he once said that more than half of all the people who ever lived are alive today. This is also not true, but it makes for some interesting claims at parties.

[GOURDHEAD]

Likewise he once said that more than half of all the people who ever lived are alive today

How would Clark or anyone go about guessing how many people have ever lived? How far back "down" the evolutionary tree would individuals be counted as human?

[antoniseb]

Originally posted by GOURDHEAD@Mar 20 2004, 08:04 PM
How would Clark or anyone go about guessing how many people have ever lived?

It's not too hard to guess how many people had ever lived, but you're right about needing to establish a cut-off point going backwards. I'd pick sometime after about 75,000 BCE, when the population was reduced to about 1500 humans [based on genetic data]. Other's might take a more bibical approach and go to 4004 BC, when some sources say the world population was two.

I'm sure Clarke was winging it on the statement, but that it was about the population explosion.

As to estimating the total number of people, there is a field of study that does exactly that for specific periods. Construct a curve, and integrate under it. There have probably been between fifty and a hundred billion people.

[errorist]

How about a comet made of oxygen about the size of Earth slamming into it. Not impossible we already saw a comet hit it about ten years ago.

[damienpaul]

perhaps we scout around the KBO's and launch a few Sedna's and Pluto's at jupiter...what would happen to jupiter if it were bombarded by heaps of KBO's?

[errorist]

With all that H2 and introduce O2!!!! KABOOOOOOOOOOOOOOOOOOOOOOOOM!!!!&# 33;

[damienpaul]

This leads me to the subsidary question - how many KBO's will it take to turn on Jupiter's lightglobe?

[errorist]

Possibly one if it is big enough, and made of the right stuff!!!

[antoniseb]

Originally posted by errorist@Mar 21 2004, 03:32 AM
Possibly one if it is big enough, and made of the right stuff!!!

Big enough would be 74 times the mass of Jupiter. The right stuff would include plenty of lithium. Please note that a chemical reaction from lots of Oxygen mixing with Jupiter's hydrogen atmosphere would not ignite fusion in the core of the planet. It would quickly blow a hot cloud of water vapor into Jupiter's upper atmosphere. That would certainly be a spectacular event but it would not turn Jupiter into a star.

[VanderL]

It would quickly blow a hot cloud of water vapor into Jupiter's upper atmosphere. That would certainly be a spectacular event but it would not turn Jupiter into a star.

Doesn't that count as ignition?
Seriously, what about brown dwarves, there are brown dwarves that have "flared", meaning that some process can account for starlike behaviour in objects that are thought to be too light to be a star. How do we know exactly what the limit is before fusion happens. And can we be absolutely, 100% certain that fusion is the power source of a star?

Cheers.

[antoniseb]

Originally posted by VanderL@Mar 21 2004, 04:57 PM
can we be absolutely, 100% certain that fusion is the power source of a star?

The fusion model explains the observed phenomena very well.

[VanderL]

The fusion model does not explain very well everything that is happening at the Sun's surface, plus it doesn't explain very well why the solar wind can just stop (in may 1999), or why there is a solar cycle of appr. 11 years, or why the "bottom" of a sunspot is cooler than the surface.
That doesn't mean it is wrong, but there is still a lot that a fusion model cannot explain (magnetohydrodynamics, brr).
That as an aside, but more important for this topic, what is the lower limit for fusion and how can we explain the flares of brown dwarves??

Cheers.

[damienpaul]

There are flares on brown dwarves? I know that Jupiter is not strictly speaking considerd to be a brown dwarf, but does it 'flare'?

[antoniseb]

Originally posted by damienpaul@Mar 22 2004, 02:48 AM
There are flares on brown dwarves? I know that Jupiter is not strictly speaking considerd to be a brown dwarf, but does it 'flare'?

This is not my main area of interest. Hopefully someone with more facts will follow up.

There haven't been a lot of observed 'flares' on Brown Dwarfs, but that may because we've had so little telescope time observing them. The only articles I've seen on the subject had to do with Chandra observations that showed some X-Ray flaring on one particular nearby Brown Dwarf. It was speculated that this was the result of a magnetic storm. There is no indication that these were because of brief periods of fusion.

I have the impression that Jupiter also has some mild X-Ray activity. Some is associated with auroras [sun related]. I think I recall that some X-Ray stuff from Jupiter associated with lightning storms, but I am uncertain about this, so if it matters, you'll have to look it up, or wait for a better reply.

[Tim Thompson]

VanderL: The fusion model does not explain very well everything that is happening at the Sun's surface, plus it doesn't explain very well why the solar wind can just stop (in may 1999), or why there is a solar cycle of appr. 11 years, or why the "bottom" of a sunspot is cooler than the surface.

But, as far as these phenomena are concerned, the fusion model is irrelevant. The outer layers of the sun are thoroughly insulated from the deep interior, as far as radiative transfer is concerned, so the mechanism whereby energy is generated does not matter (only the presence of the energy matters). The details of what happens at the sun's surface are dominated by the local plasma physics, and the behavior of sunspots is in fact well understood in light of very standard solar theory (i.e., Theories of solar eruptions: a review, Lin, Soon & Baliunas, New Astronomy Reviews 47(2): 53-84, April 2003; Sunspots: An overview, S.K. Solanki, The Astronomy and Astrophysics Review 11(2-3): 153-286, 2003, the links are for abstracts only, the papers are not online that I know of). The cause of the solar cylce is less well known, but then it is not explained by any of the alternative theories either, nor is the sudden and temporary cessation of the solar wind. But there is nothing about either of these phemomena to suggest that standard theory will not explain them.

For instance, the mechanism that accelerates the solar wind is certainly local, and varies considerably over the surface of the sun, which is why the solar wind is clumpy. A redistribition of magnetic energy in the turbulent plasma of the photosphere (or higher in the solar atmosphere) could well explain observed glitches in the solar wind.

As for ignitng Jupiter, the minimum mass for a star in standard theory is about 0.08 solar masses, and Jupiter is about 0.001 solar masses, so make it 80 times more massive and you get a minimum mass red dwarf star, that survives like the sun via hydorgen (proton) fusion. However, in the range of roughly 13 - 80 Jupiter masses, the central temperature should be high enough to fuse deuterium (proton+neurteon), but with a very much smaller return on the energy. That's a kind of ignition, just not so dramatic.

Red dwarf strars & brown dwarfs can be very active in flaring. The most likely reason is that for objects of such low mass, the convective zone penetrates all the way to the core (not so for the sun). That deep convection will twist the magnetic field lines more dramatically than happens for a solar type star, and it's that twisting of the magnetic field that prvides the energy for the flare, not the internal ignition source. In other words, the fusion model is also not relevant to flaring because it's not the energy source that drives the flares.

All of this is available in the standard textbooks on stellar interiors & atmospheres, of which there are many. It's just that the material is not amenable to "general" readers, and is intended for scientists & students of stellar physics. A good place to start on the web is Our Sun and Stellar Structure.

[VanderL]

Thanks Tim that's all very reassuring; the standard model explains it all. There is a problem though in the radiation of heat outwards, layering is needed (and all kinds of zones are postulated, even a neutrino oscillation zone must be there inside our Sun somewhere) and all the equations that explain what is happening inside the Sun are totally disconnected from the Solar surface. That's exactly why the standard model is not explaining the stuff happening at the surface; no connection is supposed, because there is no way that this can be compatible. Brown dwarves are thought to be completely different from normal stars, although they have evolved similarly. This would mean that every celestial body needs a very specific set of circumstances to become what they are (black holes, stars, dwarves, planets etc). That's exactly where I see a problem, there are no intermediates, everything is black or white ( brown/red in this case).

The most likely reason is that for objects of such low mass, the convective zone penetrates all the way to the core (not so for the sun). That deep convection will twist the magnetic field lines more dramatically than happens for a solar type star, and it's that twisting of the magnetic field that prvides the energy for the flare, not the internal ignition source. In other words, the fusion model is also not relevant to flaring because it's not the energy source that drives the flares.

Al of this is assumed, and nothing is proven, there's a lot more needed to make all these claims stick (at least for me), and when all else fails there's always magnetism to the rescue. There is no reason for magnetism to be important in stars, but there is clearly something happening that makes magnetism important, but all the evidence is buried deep down inside stars, safely hidden from direct probing.

VanderL: The fusion model does not explain very well everything that is happening at the Sun's surface, plus it doesn't explain very well why the solar wind can just stop (in may 1999), or why there is a solar cycle of appr. 11 years, or why the "bottom" of a sunspot is cooler than the surface.

But, as far as these phenomena are concerned, the fusion model is irrelevant.

Not true, any model should explain all phenomena, if there things outside the model than we need new models, that incorporate these phenomena.

Cheers.

[TheThorn]

Originally posted by VanderL@Mar 22 2004, 11:07 PM

But, as far as these phenomena are concerned, the fusion model is irrelevant.

Not true, any model should explain all phenomena, if there things outside the model than we need new models, that incorporate these phenomena.

But, VarndeL, that's just silly.

The Natural Selection model of Evolution doesn't try to explain the weather in China next Thursday. Doesn't have to even try. The two phenomena are disjoint.

The source of the energy in the sun (be it fusion, gravitational collapse, electricity, or hamster power) is disjoint from the magnetic effects on the surface of the sun, which are also disjoint from the change in allele frequency through generations within a population of organisms. We can deal with the three phenomena with three different theories - we don't need one collossal theory to explain it all.

[Tim Thompson]

Of course the standard model does not "explain it all", but that's not the point. This is the point ...

There is a problem though in the radiation of heat outwards, layering is needed (and all kinds of zones are postulated, even a neutrino oscillation zone must be there inside our Sun somewhere) and all the equations that explain what is happening inside the Sun are totally disconnected from the Solar surface.

Everything you have said here is wrong, all of it. You can't generate a reasonable criticism of the standard model for the simple reason that you don't know what the standard model is. None of the "layers" you talk about are postulated anywhere in any standard theory. And the equations that define the physical state of the interior are in fact intimately connected to the surface of the star.

I suggest you take some time to find out what the solar models really look like. One good way to start is to visit the standard solar models webpage from John Bahcall. These are the technical papers that describe the solar models in some detail, and will give you a much better feel for what's going on.

There is no reason for magnetism to be important in stars

As a physicist, all I can say is that this is absurd. There is every reason for mangetism to be not just "important", but critical to the behavior of the stellar photosphere & atmosphere. It is less critical to the state of the stellar interior, though certainly not negligible. It is least important below the convective zone, where the magnetic field has a hard time getting in.

... any model should explain all phenomena ...

And this too is quite literally unbelievable. No model should ever be expected to explain "everything". Any model should be expected to explain what it is designed to explain, and anything more than that is, as they say, "gravey".

For instance, the nuclear fusion model is intended to explain where the star gets its energy. But nucelar fusion only happens in the deep interior, maybe in the central 1/3 of the sun, but more so deeper in. The photons generated as gamma rays in the nuclear reactions are completely thermalized, fairly rapidly. By the time they reach the outer regions (about 1,000,000 years later), all connection between the radiant energy and how it was generated is lost, and that is independent of the model for generating the energy. Any source of energy that is interior to the star will behave in the same manner, because the interior plasma is too dense. So there is no connection between the model and the surface, because the energy that reaches the surface, does not "know" how it was created. It only matters that the energy is there.

We all know full well that there are as yet unexplained phenomena in, on & around the sun. But you seem to think that the mere fact that an explanation is not now on the table is proof that there cannot ever be one, and I find that a rather bizarre approach to understanding nature.

That the interior energy of the sun & stars is generated by fusion reactions is, as far as i am concerned, a simple fact of observation. It is consistent in every way with what we know must be happening physically inside the star, and it is consistent with the number and energy spectrum of neutrinos observed coming from the sun, which can only be created (so far as we know) by nuclear reactions. There are plenty of un-obvious thing to study in science, and it seems to me a useless exercise to worry so much over something that is really just too obvious.

[damienpaul]

Very interesting stuff, now if I am understanding correctly, Jupiter would have to be seriously beefed up to get any kind of Arthur C Clarkes 2010 action happening.

The amount of energy produced by Jupiter, what proportion is it compared to the sun, I know the amount will be far less than the sun's but by how much?

[Planetwatcher]

Guys, guys;

Don't be rediculas. You were already told that Jupiter would have to have 75 times more mass then it does now.

That means you can add Saturn, Uranus, Neptune, all the other planets, asteroids, moons, comets, and Kupier objects, and still come up needing over 70 times more mass.

You could do all that combining and throw a bunch of solar flares at it and it still will not begin a fussion reaction. It likely will react, but not with fussion.

[Tim Thompson]

The amount of energy produced by Jupiter, what proportion is it compared to the sun, I know the amount will be far less than the sun's but by how much?

Easy. The effective temperature of Jupiter is about 134 Kelvins, and for the sun it's about 5777 K. From the Stefan-Boltzmann law, we know that the total thermal energy emitted by a body at any give temperature is proportional to the temperature to the 4th power. So the answer to your question is just the ratio of the 4th power of the temperatures.

(5777/134)^4 = 3,454,540

That's ignoring non-thermal sources of energy, which can be significant in both cases. Jupiter has a highly variable radio emission due to electrons trapped in the magnetic field. The sun has a highly variable X-ray emission for the same reason, but the electrons trapped in the solar magnetic field are far more energetic than those around Jupiter. Add in the non-thermal sources, and I'm sure the number will be a bit larger in favor of the sun.

[TheThorn]

Uhh, Tim, I think you may have missed a factor there, unless I'm mistaken, which wouldn't be the first time.

The sun's diameter is approximately 10 times Jupiters. So its surface area is 100 times as big. So, even if they were at the same temperature, the sun would have to generate 100 times as much energy as Jupiter.

So, I think your answer should have been 10^2*(5777/134)^4 = 345,454,000

No?

[Tim Thompson]

Oops. I had quite forgotten, in my haste to look brilliant, that the Stefan-Boltzmann constant has a unit surface area in it. I am appropriately apologetic.

[damienpaul]

ah you still look brilliant Dr. T!

[Faulkner]

So Jupiter can still blow up?

Maybe Jupiter is our binary star yet to FUSE!!!!!!