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imported_Draco
2003-Sep-06, 06:38 AM
Of our solar system?! ;)
Or at least half the size of our solar system? In a galaxy far away!

Planetwatcher
2003-Sep-07, 04:25 AM
Not likely anywhere that big. Our whole solar system is over 20 billion miles accross, by the time you go the the edge of the Kupier belt to the other side.

The biggest discovered so far was like 15 times or so the size of Jupiter.
Much larger, and it's own gravity, and friction would likely start a nuclear fusion reaction which is what powers our Sun.

Now some stars can become as big as Saturn's orbit, which is nearly a billion miles accross. Consider Betlegese a red supergiant more then 500 light years away.
It is a varible star meaning it varies in size, (current theories conclude it may be close to exploding into a supernova)
It gets as big as Jupiter's orbit.

There are larger objects yet, known as quazi steller objects, usually called quazars,
are believed to be as big as many galaxies. They release enough energy to make our largest local stars look like AA Energiser batteries. And these quazers do keep going and going.

So the short simple anwser is planets? No. Other objects? Yes.

imported_Draco
2003-Sep-07, 10:57 AM
Thank you for that:)
Highly interesting!
A sun that big? whoa! Imagine all the radiation that is being emitted!

Josh
2003-Sep-07, 04:08 PM
A Dyson sphere, while not a naturally formed planet nor anything that has been observed as yet, would be, by definition, a comparable size to the solar system.

So maybe it's not really a planet but it has planet like qualities...or inverted planet like qualities...




(I am back from overseas and will resume posting. I got to see big ol' Mars from Australia, France and Italy! ... beautiful wherever I looked at it.)

imported_Draco
2003-Sep-08, 05:59 AM
I never knew that too!
Cool, must have had fun in those places?:)

Josh
2003-Sep-08, 11:36 AM
A Dyson sphere is only theoretical ... I don't know if i made that clear.

Planetwatcher
2003-Sep-09, 11:05 PM
I was going to say that about the Dyson sphere but didn't want to confuse the young man.
Dyson's sphere is a sci fi theory at that. It was propounded in Star Trek The Next Generation, in the episode in
which Scotty is retrieved by the Enterprise crew in the 24th century.

Anyway, in it's theory, it is supposed to be possible to build a giant metal sphere around a star at the distance it
would take for life to survive. All the stars energy would provide life and the people would actually live on the
inside wall of the sphere where the star never rises or sets, but provides energy all the time.

Anyone outside would not be able to see the star or detect the sphere until they almost crashed into it.

But there are a whole set of other problems which would go with it if it were actually possible to construct a man
made sphere which is more then 200 million miles accross. Or hundreds of thousands times larger then Earth.
This is nothing but a theory within a fictious story.

Vince Fukes
2003-Sep-09, 11:34 PM
Larry Niven wrote the "Ringworld" book which he created a ribbon orbiting a star, In the second book he thanked all the fans that had contacted him with the various technical problems and specifications of the ring.

But the real issue I have with Dyson spheres is not the difficulty in getting a bazillion tons of material formed into a hollow ball, but hee central star would be constantly pumping out various radiation into an enclosed space. In the ringworld there were shadow squares that blocked the "sun", but inside a sphere such devices would have nowhere to radiate thier captured heat.

It would be like when the clothes dryer is on in the laundry. If the door is closed so we can hear the tv, then the laundry room rapidly heats up and fills with condensation. THe dyson sphere would need a BIG door to be left open or the heat would build up until it burst.

SO Mr. Niven was probably correct in sticking to a strip in orbit then the remaining heat/light/radiaition could safely escape the system.

just my 2 cents worth ( that AUssie cents so only 1US and barely a penny UK :)

v

Josh
2003-Sep-10, 04:57 AM
A Dyson Sphere was used in star trek, but the original idea comes from a Brit named Freeman Dyson who postulated their existence in 1959. I have no idea if he was the first but he got the name.

What's more...I figure that if a civilization were able to create a Dyson Sphere then they'd also have figured out a way to block or dissipate the radiation. Originally, the idea was that the dyson sphere wouldn't be continuous but rather only have enough area to capture the desired amount of sunlight and therefore, energy.

That's a lot of brickies needed for that job. I know here in australia brick layers are paid $1 per brick. someone could make a lot of money! Now ... where to get the bricks from is another problem.


...to add another idea in there, if you wanted to live there it would probably be more practicable to create a shell around Jupiter at some distance where the gravity would be earth-like and then tap energy from the planet. I think that's called Super (or Supra) Jupiter theory (?).

QJones
2003-Sep-13, 12:37 AM
The one problem with putting people on a Ringworld or whatever is that they have trouble producing resources. The only resource they could develop is either manufacturing outside resources (ie. making cars outta imported steel) or scientific discoveries.

People wouldn't be as productive as if you put them on a planet and told them to start working on civilization





Live long enough to see Space! (http://www.longevitymeme.com)

Deep_Eye
2003-Sep-13, 01:08 AM
Sorry, I'm replying sort of late, but isnt it quasars? (with an s not a z) or are they two different things?

zephyr46
2003-Oct-17, 06:03 AM
The Pistol star (http://www.solstation.com/x-objects/pistol.htm) is to my knowlege the largest star. I think the motivation for a dyson sphere would be around a red white or brown dwarf to an advanced civilisation that could not reach another star and their star were dying, the point being to capture as much energy as possible, certainly an answer to urban sprawl.

Matthew
2003-Oct-17, 07:08 AM
You could mine metal off various planets, only a few thousand or so would need to be mined of metal to build a Dyson sphere.

Haglund
2003-Oct-17, 07:25 AM
One would think that a civilization advanced enough to successfully build a Dyson sphere (something that makes our largest and proudest buildings and constructions look like child's play) would have the technology for interstellar travel as well, even if they would reach only a few percent of c they could build generationships or perhaps use cryogenics or something.

Matthew
2003-Oct-17, 07:57 AM
If a civilisation had the ability to build a Dyson sphere, wouldn't they be technologically advanced for interstellar travel? If so, wouldn't it almost be esier to send most, if not all to another planet which you could inhabit?

Dium
2003-Oct-17, 10:24 AM
Originally posted by Planetwatcher@Sep 7 2003, 04:25 AM
There are larger objects yet, known as quazi steller objects, usually called quazars,
are believed to be as big as many galaxies. They release enough energy to make our largest local stars look like AA Energiser batteries. And these quazers do keep going and going.

Yes, but if I remember correctly, quasars are galaxies. They are galaxies with very active nucleus. They are just so far away that they appear point-like (star-like). So, indeed, stars would seem like AA batteries compared to them, but wouldn't the same be with any galaxy. :)


Parker wrote:
"would have the technology for interstellar travel as well, even if they would reach only a few percent of c they could build generationships or perhaps use cryogenics or something."

Interstellar travel would be needed to get enough materials. A civilization capable to make a Dyson's sphere would probably have longer life-span for its citizens, though. So traveling might not be a big problem. Speed might not be either. If you are going to build something as large as a Dyson's sphere, you are probably not in a hurry to do so. Stars last for billions of years so that's how long you'll be using that sphere. You could just send thousands of ships to thousands other solar systems and wait for them to return with the materials in 1000 years or maybe in 10000 years. Or maybe even more. Once returned you can start building it and even that could take thousands of years to do. If the civilization is patient enough, the whole process might take 100,000 years or more, maybe millions. The point is that when it's build you can enjoy it for billions of years until the home star becomes unstable. And even after that you could just dismantle it and transfer to another star. So even a million years is nothing compared to all those billions and billions of years you'll be using it.

starrman
2003-Oct-17, 09:41 PM
Keep in mind as well that a Dyson Sphere, in order to perfom its intended function of "mining energy" from the parent star, need be no more substantial than spiderweb. A fine net, with a weave measured in hundreds of thousands of miles and orbiting at a distance of, say, the asteroid belt, would still result in surface area sufficient to capture a substantial percentage of a star's energy output. This could be accomplished with a (relatively) minor investment of raw material, very likey without the necessity of requiring interstellar travel to obtain those "brickies."

John

Planetwatcher
2003-Oct-20, 02:56 AM
Yes, but if I remember correctly, quasars are galaxies. They are galaxies with very active nucleus. They are just so far away that they appear point-like (star-like).

I disaggree. A quasar (quasi-steller object) is a single celstrial body, unlike a galaxy which is many many individual stars within a very large cluster

You can almost think of a galaxy as a super solar system, except it is made up of the stars and everything in all the star systems, all orbiting a central point of gravity.
A quasar contains no stars, no planets, no moons, no asteroids, no comets, no black holes, or nebula remains. It is a single extra-ultra-super-super-super star.

starrman
2003-Oct-20, 03:25 AM
I would be very eager to learn your sources for the assertion that a quasar is "a single celestial body." As far as I am aware, the structural nature of quasars remains unknown, but I'd be delighted to learn otherwise.

John

imported_Draco
2003-Oct-20, 03:35 AM
This probably isn't related...but isn't the sun going to expand 2000 times its normal size when it is nearing its death?

starrman
2003-Oct-20, 03:59 AM
If memory serves, the prediction is that Old Sol, when it evolves to its red giant phase, will reach out to about the orbit of mars.

John

Dave Mitsky
2003-Oct-20, 08:37 AM
"It is a single extra-ultra-super-super-super star."

That is not the commonly accepted explanation.

http://kurp-www.hut.fi/edu/merja-AGN/AGN-l...des/slide4.html (http://kurp-www.hut.fi/edu/merja-AGN/AGN-lecture1-slides/slide4.html)

http://www.astr.ua.edu/keel/agn/quasar40.html

http://www.tufts.edu/as/wright_center/cosm...text_gal_5.html (http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_gal_5.html)

Dave Mitsky

starrman
2003-Oct-20, 08:45 AM
Thanks for the useful links.

zephyr46
2003-Oct-22, 02:46 AM
If a civilisation had the ability to build a Dyson sphere, wouldn't they be technologically advanced for interstellar travel?, I don't see the connection? I could see us building a dyson sphere before we get anywhere near even proxima :D

I wonder whether a dyson shpere at the asteroid belt need be more than a ring, held in position and drawing energy from magnetic induction off the suns magnetic feild? does it extend that far out ? anyone ?

Haglund
2003-Oct-22, 09:48 AM
Well I doubt there's enough matter in the solar system to build a solid closed dyson sphere. But then we could build an open sphere consisting of independently orbiting parts forming a sphere, which would be much easier to build. Still it would be a project of incredible proportions, to build such a sphere to cover most of the star at, say 1 or 1.5 AU or something. My personal guess is that before we have finished that, we will have gone to Proxima and maybe other stars too. But who knows? Maybe with nanotechnology one could begin by transforming the asteroidbelt into a ring, as you say. But I think that a first step towards truly harvesting our star is to build a ring of independently orbiting solar powerplants in geostationary orbit. This could happen within a hundred years.

Planetwatcher
2003-Oct-22, 04:33 PM
Thankyou David for the links as well.

Okay Starman, I stand corrected. :ph34r:
At least I got right that quasars put out enormus amounts of energy. Especially radio energy and light and with the variations noted in David's links.

Mercator
2003-Oct-23, 02:58 AM
I dont see the problem with Dyson's spheres .... shouldn't they be able to just heat up until they reach equilibrium, and then not get any hotter? The outside of the sphere would just look like an extremely large, extremely cold star to the outside universe.

I'm not very well educated on astronomy ... I'm a meteorology student, but I do hope this idea works so I can use it in a science fiction story. Am I right about the lack of a problem with the radiation coming from the sun?

zephyr46
2003-Oct-23, 05:23 AM
Okay Starman, I stand corrected.

I wasn't going to say anything planetwatcher (love your favorite object string :) )
but I wonder how big a star could get ? The Pistol Star (http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?The+pistol+star) seems to suggest that it reaches a limit and throws it's weight off, I thought current thinking was that it would start collapsing under it's own weight and for a black hole or go super nova, I think planet watchers line of thought is interesting, I think of galaxys as cyclones with an eyes or black holes. Quasars or AGN maybe represent somthing of a black hole limit of loading, thus you have a neutron star packing a galactic size gravity and a corona of electrons, positrons and proton emiting energy as the provide a shifting feild preventing each other from entering. So the black hole, neutron star or pulsar core could be the largest star possible ?

Matthew
2003-Oct-23, 07:26 AM
zephyr46, when you say largest do you mean in size, density, mass?

A black hole has the greatest density, certain black holes have the greatest mass, and certain black holes have the greatest size. But the average star would be larger (in size) than a black hole.