Sun question.

science_man · Jun 14, 2007

Does the sun revolve around its own axis or is it relatively stable? In other words does the sun make little circles around a certain axis ; and also does the sun spin in it's own axis?

MeteorWayne · Jun 14, 2007

Yes the sun spins on it's axis. However, since it is a gas, the equator and the poles rotate at different speeds; about 27 days at the equator. And actually the sun's position does make a positional wobble as the barycenter of the solar system shifts due to the mass and position of Jupiter, Saturn, Uranus, and Neptune. I'll pull up a post with the details. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

docm · Jun 14, 2007

Sol rotates on its axis once every 25.38 days (25 days 9 hrs 7 min 13 sec) at the equator and its axis is at an angle of 7.25 degrees relative to Earths orbital plane. I've not seen any numbers for its axis preceding. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Jun 14, 2007

Yes I did not mean precession, I meant cycles around the barycenter. It's unclear in the OP which is being refrerred to, but your interpretation is probably correct. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

why06 · Jun 14, 2007

"However, since it is a gas, the equator and the poles rotate at different speeds; about 27 days at the equator.... " It is a gas?... I thought it was made up by some sort of degenerate matter... like metallic hydrogen... <div class="Discussion_UserSignature"> <div>________________________________________ </div><div><ul><li>your move...</li></ul></div> </div>

enigma10 · Jun 15, 2007

Hydrogen 91.2 % Helium 8.7 % Oxygen 0.078 % Carbon 0.043 % Nitrogen 0.0088 % Silicon 0.0045 % Magnesium 0.0038 % Neon 0.0035% Iron 0.0030 % Sulfur 0.0015% Though some of the matter at the center of the sun may be in a form of degenerated matter, for the most part it is still in Nuclear Fusion, with the occasional rogue collection of positively charged ions, largely made up of helium and carbon nuclei, surrounded by unbound electrons. <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

derekmcd · Jun 15, 2007

Metallic hydrogen is a form of degenerate matter found in the interior of planets such as jupiter and saturn. Referring to the sun as gas is not technically wrong. Plasma is really nothing more than superheated gas that is ionized. Degenerate matter is when that plasma becomes a solid again under enormous pressures. I could be wrong, but I don't believe the sun is in a state of degenerate matter at the core. Only the core of massive stars will be in a degenerate state along with white dwarves, neutron stars and black holes. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

docm · Jun 15, 2007

Interesting Sun core factoids; Density: 150x that of water Output/volume: 6 Î¼W/kg (human body = 1.2 W/kg) It's high total output is all in the economics of scale. <div class="Discussion_UserSignature"> </div>

emperor_of_localgroup · Jun 15, 2007

Forgive my ignorance about our own solar system. A few apparently dumb questions about our solar system have always bugged me. An inquiring mind wants to know. 1) Why doesn't the sun explode? If explosive materials are kept close together, one explosion should cause the entire sun to explode in seconds. Isn't it some type of controlled reaction? Or do the materials replenish themselves which made the nuclear reactions possible for billions of years without significant abatement? 2) This is not about the sun. Why are the planets Jupiter and Saturn gas? If gravity can make incredible things like black holes , shouldn't billions of years of gravitational pull , doesn't matter how weak and slow, make the planets solid now? Too much spin? I know astronomers have explanations for these silly questions. <div class="Discussion_UserSignature"> Earth is Boring </div>

MeteorWayne · Jun 15, 2007

"1) Why doesn't the sun explode? If explosive materials are kept close together, one explosion should cause the entire sun to explode in seconds. Isn't it some type of controlled reaction? Or do the materials replenish themselves which made the nuclear reactions possible for billions of years without significant abatement? " The simple answer is gravity. It's stronger than the energy from the fusion. In fact these two forces are in balance, that's what makes a star work. "2) This is not about the sun. Why are the planets Jupiter and Saturn gas? If gravity can make incredible things like black holes , shouldn't billions of years of gravitational pull , doesn't matter how weak and slow, make the planets solid now? Too much spin" The simple answer is: gravity is not strong enough to overcome the resistance of nuclear and gas pressure forces. The sun is very massive (over 99% of the mass of the entire solar system) By comparison Jupiter and Saturn are very lightweight. Uranus and Neptune, much smaller still. And all the rest; mere dust in the wind <img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

docm · Jun 15, 2007

1. the sun is like a continuously exploding H-Bomb. Its heat tries to make it blow apart, but its intense gravity holds it together. The equilibrium of these forces give it a stability that should last another few billion years, though its temperature will rise sooner than that. 2. As with the sun there is an equilibrium at work with the gas planets. None have enough mass to collapse and ignite as a star or brown dwarf but neither do they have enough internal heat to expand, even though they are quite hot internally; 7,000K for Uranus & Neptune to />20,000K for Jupiter. They may even have a rocky or metallic core, so IMO if that is the case one could think of them as solid planets with very deep & thick, or even partially liquefied, atmospheres. <div class="Discussion_UserSignature"> </div>

emperor_of_localgroup · Jun 15, 2007

Hope you and Meteor are correct on this explanation, not just theoretical cover ups. Explanation for the sun seems very reasonable, 99% of mass of the solar system is in the sun. But explanations for the gas planets appear to be on a little shaky ground. We here are talking about billions of years. Gas can move around, flows from one point to another causing change in pressure, there is no explosion like on the sun, gravity should gradually in billion years win over the pressure and temperature. Earth core is also extremely hot, its temperature couldn't prevent it from becoming a solid. Anyway, thanks for spreading the knowledge. <div class="Discussion_UserSignature"> Earth is Boring </div>

docm · Jun 15, 2007

FYI just because millions of years pass doesn't mean a body will keep on shrinking from gravity induced compression. Ever try to squeeze a billiard ball to make it shrink? Well, your hands are thousands of times stronger than the force of gravity and still neither is up to the task. Gravity is really a very weak force except at large scales, and even then the mutual repulsion of the electron shells in an objects atoms is far more than enough to balance gravity in objects like planets and billiard balls. This electron shell repulsion is what stops gravity from pulling you through the floor and on down through the Earth to its core. How much mass would it take for gravity to become strong enough to override matters resistance and create a black hole? Several solar masses, and even then only once the stars fuel has run out and it can't generate enough heat to prevent collapse to a critical density. Here it will either become a black hole or rebounding shock waves blow off enough mass for it to become a white dwarf, neutron star or quark star. <div class="Discussion_UserSignature"> </div>

tony873004 · Jun 19, 2007

Here's an image of the path the Sun makes over the course of about 1 century. http://orbitsimulator.com/BA/ssBarycenter.GIF

MeteorWayne · Jun 19, 2007

Hey thanx tony. I've talked about the barycenter in a few threads before, it's great to see an image. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

Saiph · Jun 19, 2007

in both cases emperor, it's a matter of equilibrium. The sun is contained by gravity, and it's fusion tries to cause the sun to expand. However, the strenght of the fusion reaction in the core (or rather it's intensity) is determined by how dense the core is. If the fusion reaction increases, the sun will expand (fusion overpowers gravity). Unfortunately, that also spreads the energy out, allowing the sun to cool, and the fusion reaction slows...allowing gravity to take over and collapse the star. Our sun is currently in a state of equilibrium, these expansion and contraction phases are very very small. However, this will not always be the case (and hasn't always been either). At some point our star will become unballanced, due to the presence of fusion waste products in the core. The result will be one of many types of variable stars. With gas giant planets, it isn't fusion that's resisting gravity, but just the pressure of the particles against eachother. Slight correction, the sun's gravity is also resisted by the pressure of the particles, however without the central fusion reaction, the particles aren't energetic enough to provide sufficient pressure. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

3488 · Jun 20, 2007

Another interesting point is that the Sun is almost like Uranus, with respect to its axial tilt. It is tilted by about 78 degrees. With respect to the galactic centre, the Sun is having late 'September' at the moment with the Sun's nothern hemisphere close to its 'Autumn equinox' with respect to the centre of the Milky Way. It was close to 'mid Summer' when the dinosaurs became extinct at the KT boundary!!!!!!!!! Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

emperor_of_localgroup · Jun 20, 2007

The question I raised has come from our everyday observations of explosions. Usually one explosion triggers another if explosive materials are present within the boundary of the first explosion. From the sun's age we can somehow conclude: 1) Some type of controlled fusion reactions are taking place on the sun. Because uncontrolled reactions may lead to an explosion (or a burn up) in a very short time. or 2) One reaction (or a group of reactions) is taking place far outside the boundary of another reaction (another group of reactions). Here are a couple of questions to all. 1) Has any one calculated how many fusion reactions are taking place on the sun per sec or per min or per cubic kilometer, etc? This calculation wont be difficult given the amount of radiation energy received here on earth. 2) What are the conditions that must be met to start a fusion reaction on the sun? Is it only gravity? Now, one more thought about gas planets. In all these explanations of gas planets, I haven't heard of the role of a planet's distance from the sun. The planets near the sun are clearly solids, but planets beyond Mars tend to be gas. Doesn't sun light play a role in making 'ice planets'? <div class="Discussion_UserSignature"> Earth is Boring </div>

MeteorWayne · Jun 20, 2007

1) Has any one calculated how many fusion reactions are taking place on the sun per sec or per min or per cubic kilometer, etc? This calculation wont be difficult given the amount of radiation energy received here on earth. Yes it has been calculated, I don't have have the figures here. 2) What are the conditions that must be met to start a fusion reaction on the sun? Is it only gravity? More or less. It's gravity that raises the temperature, the combination is what permits fusion. Now, one more thought about gas planets. In all these explanations of gas planets, I haven't heard of the role of a planet's distance from the sun. The planets near the sun are clearly solids, but planets beyond Mars tend to be gas. Doesn't sun light play a role in making 'ice planets'? Not now, but 4 1/2 billion years ago when the planets were forming, it did make a difference. It was much hotter in the inner solar system, and colder further out. So it seems likely that gases were easily blown away close to the sun, and more likely to condense further out. MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

heyscottie · Jun 21, 2007

emperor: Having a "runaway" fusion reaction like you suggest is actually quite difficult. The only thing that allows fusion to occur is extremely high temperatures or pressures. But the reaction tends to counteract any high pressures by blowing the matter apart with its own energy...

observer7 · Jun 21, 2007

From Wikipedia (and these are very close to what I remember from my Masters program) About 3.4Ã—1038 protons (hydrogen nuclei) are converted into helium nuclei every second (out of about ~8.9Ã—1056 total amount of free protons in Sun), releasing energy at the matter-energy conversion rate of 4.26 million tonnes per second, 383 yottawatts (383Ã—1024 W) or 9.15Ã—1010 megatons of TNT per second. The fusion reaction starts due the heating of the primordial cloud caused by pressure from gravitaional collapse. As the primoedial cloud continues to grow and acquire mass, the temperature at the core rises. When it reaches several million degrees the process of fusion begins. The force of gravity is then counterbalanced by the outward pressure of the heat from the fusion reaction. Also, one thing that always gets me is the rate of conversion (4.26 million tons per second!!) of hydrogen to energy. The amount of matter that makes up our Sun is just mind boggling. (Because that rate has been fairly constant for about 4 BILLION years!) http://en.wikipedia.org/wiki/Sun -- <div class="Discussion_UserSignature"> "Time exists so that everything doesn't happen at once" Albert Einstein </div>

emperor_of_localgroup · Jun 22, 2007

Your numbers seem correct. At this rate of 3.4x10^38 per sec it will take another 80 billion years to spend up all of 8.9x10^56 protons. Here is another interesting number: in the last 4 billion years , at the above rate, the sun used up almost 4.3x10^54 protons, which is almost 1/20 th of the current number of protons. Does it mean the sun was 1/20th times larger (or smaller?) of its current size 4 billion years ago? Because astronomers are saying the sun will expand in its dieing times due to loss of gravity. The amount of matter that makes up our Sun is just mind boggling. (Because that rate has been fairly constant for about 4 BILLION years!) It's not the amount of matter that bugs me it's the unbelievable 'constancy' of astronomical objects over such a long long period of time. There is no record, in last 5000 years some one noticed and said, 'the sun suddenly went dim for a few hours' (ignore the clouds and eclipses). I understand mathematically they can be clearly explained, but he sun, motions and rotations of the planets are so perfect one has to wonder 'is there something else than what we see'? One possibility may be fusion materials somehow recycle in the sun, just as our earth atmosphere recycles. The same can be said about the gases of gas planets. <div class="Discussion_UserSignature"> Earth is Boring </div>

nexium · Jun 22, 2007

The sun was likely bigger, more massive and hotter about the time it made the transition from protostar to main sequence. In a few million years it settled down to more massive than now, but a bit smaller, because the average temperature decreased. For the past 4.5 billion years, we think the sun has slowly become hotter, thus slightly bigger inspite of losing 5% of it's mass as energy. My guess is only 1% of the suns present mass has been coverted to energy. Perhaps another 1% as solar wind. Please comment , refute and/or embellish. Neil

vandivx · Jun 22, 2007

point is the Solar system is mainly just the Sun with few negligible little chunks (planets) flying about it in the huge wastness of space and the Sun is humungous, beyond human imagination really as all cosmic measures are if you look up the numbers and think about them for a bit you'll get humble and don't even need to be christian for that <img src="/images/icons/wink.gif" /> vanDivX <div class="Discussion_UserSignature"> </div>

Saiph · Jun 24, 2007

The sun was far larger (radius wise), slightly more massive, and much, much brighter as a protostar before it hit the main sequence. It was cooler however (think red giants). As the protostar collapsed, it grew hotter so there tends to be little change in luminosity. Then the core ignites, and hydrostatic equilibrium is obtained, and the star is on the main sequence (bottom edge of the broad band to be precise). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

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