Русский New site

Advanced search

[ New messages · Forum rules · Members ]
Page 2 of 3«123»
Forum » SpaceEngine » Science and Astronomy Discussions » Main Sequence Star Surrounded by Material Closely Orbiting (Normally only found around young stars)
Main Sequence Star Surrounded by Material Closely Orbiting
WatsisnameDate: Sunday, 18.10.2015, 19:06 | Message # 16
Galaxy Architect
Group: Global Moderators
United States
Messages: 2607
Status: Offline
Quote leoskini ()
haven't Newtown theorized that a empty shell would not stay in orbit around a center of mass anyway?


Basically, yeah, if you're talking of a solid shell. The sum of gravitational force vectors on all points on the spherical shell (if the shell is uniform) is zero (i.e. they all cancel). This is true even if the central mass (the star) is not at the exact center of the shell. Therefore if the shell is originally centered around the star, but given some small push, then there will not be any restoring force to bring it back to center. It will continue to drift, until part of the shell passes through the star (oops).

Of course, any drift would be small and easy to compensate. Thinking of the sphere as stationary but measuring drift in the star relative to it, just open a hole in the side of the sphere that the star is approaching. This asymmetrical release of light will push the star in the other direction, acting as your restoring force. :)

In a Dyson swarm of disconnected objects, each object instead follows its own orbit around the star, and you could have a stable ring or spherical shell of them. Just be careful that no orbits intersect for a collision.





 
midtskogenDate: Sunday, 18.10.2015, 21:04 | Message # 17
Star Engineer
Group: Users
Norway
Messages: 1668
Status: Online
Pardon the question, but why would anyone build a Dyson sphere? Given the resources it takes it seems a pretty dumb thing to do. Just because they can?

If we possessed the required technology, how would we build a Dyson sphere anyway? Converting Jupiter into building materials? Removing it would cause other problems. And if the whole purpose is to get energy, it sounds more feasible to convert the mass of Jupiter into energy if we're comfortable with spending Jupiter, anyway. That could give more power output than the sun until we can begin spending other solar systems.

And I don't quite get what the sphere builders would need all this energy for. Storing it - by converting the energy back to matter and putting it back into the sun?





NIL DIFFICILE VOLENTI
 
DoctorOfSpaceDate: Sunday, 18.10.2015, 21:21 | Message # 18
Galaxy Architect
Group: Global Moderators
Pirate
Messages: 3595
Status: Offline
Quote midtskogen ()
Storing it - by converting the energy back to matter and putting it back into the sun?


You not only get light energy from the star, you also get antimatter and stray hydrogen/helium. It seems likely such a civilization could potentially extend the life of their star through controlled feeding.

Quote midtskogen ()
And I don't quite get what the sphere builders would need all this energy for.


Simulating entire universes within supercomputer complexes in the ring or sphere. To me the most logical long term outcome for intelligent life would be to find a very young low mass red dwarf star, build a swarm around it, and just live in VR for the next 10 to 20 trillion years. Seems unlikely any civilization would spread around a galaxy or the universe.





Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
WatsisnameDate: Sunday, 18.10.2015, 23:42 | Message # 19
Galaxy Architect
Group: Global Moderators
United States
Messages: 2607
Status: Offline
The gravitational binding energy of a gas giant makes it a highly implausible source for building materials. The work required to remove a small piece of it is enormous. Better to use small solid bodies, like asteroids and moons. You'll need the heavy elements, anyway. If you want tons of volatiles, e.g. for propulsion or fusion reactors, then slowly harvesting gas giants would make more sense, e.g. by suborbital skimmers.

Also, a Dyson sphere is probably not as expensive resource-wise as it sounds. You don't need a Jupiter mass to build one. Remember volume is proportional to r3, while area is proportional to r2. So for a thin shell (or many thin spherical segments in a swarm) a few small spherical bodies can be converted into a lot of surface area on a large sphere. A complete spherical shell with radius 0.5AU and average thickness 1cm has a volume less than Earth. Maybe even sub-millimeter is doable, in which case a few moon-sized bodies would work. What if it is micron-thickness? Then it takes a few large belt asteroids. That's not very unreasonable at all.

There are still a lot of problems with the classical Dyson sphere, however. A swarm makes much more sense from an engineering perspective.

The hardest part, I think, would be maintaining the structure, against high velocity impacts from comets and whatnot. This wouldn't be an immediate cause of failure, but rather very slowly diminish your capture efficiency. So you'd want some sort of system to detect and repair damage over time.





 
HandbananaDate: Monday, 19.10.2015, 01:42 | Message # 20
Astronaut
Group: Users
United States
Messages: 70
Status: Offline
I very relevant picture I made a while back:



In all seriousness though, Wikipedia states:

Quote
The star's large irregular changes in brightness are consistent with a large mass (or many small masses together) orbiting the star in "tight formation".[7] Several hypotheses have been proposed to explain the star's unusual light profile. Researchers currently think a possible explanation for the star's odd reduction in light may be a result of disintegrated comets orbiting the star elliptically.





Tonight... you.

Edited by Handbanana - Monday, 19.10.2015, 01:49
 
parameciumkidDate: Monday, 19.10.2015, 19:36 | Message # 21
Explorer
Group: Users
United States
Messages: 277
Status: Offline
According to today's Facebook news ticker, NASA's pointing the Allen Telescope Array at it now to look for stray radio transmissions.
Given the purported civilization's advancement, I actually don't have much hope they'll pick up much of anything, but who knows?

To elaborate:
Currently, all our transmissions are some variant of radio waves (you could maybe say microwaves aren't radio, but it's the same basic principle). But we know that's not going to work for an interplanetary civilization, let alone an interstellar one.
Say we've stranded, oh, I dunno, Matt Damon on Mars. And we want to talk to him. We could send him an email and wait a few hours for the reply, but what if something goes wrong during that time?
What we'll really be wanting is some type of FTL communication, whether that be an ingenious perversion of quantum entanglement, running an ethernet cable through a wormhole, or something else. And these, necessarily, would not propagate through "normal" space, being either directed or channeled through "subspace", "hyperspace", or whatever we call the inside of the wormhole. Long story short, aliens wouldn't be able to listen in on our chats using radio telescopes.
Turning that logic around on us, it's probable that any civilization around this mystery star is, if able to coordinate the construction of a Dyson swarm or other megastructure, using something more advanced than our equipment can pick up from here.

That said, I suppose there's reason enough to look for static from their electrical systems, etc.





Intel HD Graphics 4000 ;P
 
WatsisnameDate: Tuesday, 20.10.2015, 00:54 | Message # 22
Galaxy Architect
Group: Global Moderators
United States
Messages: 2607
Status: Offline
I am highly doubtful that we could expect ETs to be beaming radio waves at us, but not so much for FTL reasons. Spamming massive amounts of EM omnidirectionally is a very bad way to communicate unless you really want to get everyone's attention, and that's bad game theory (unless you are an Optimist like Drake and Sagan).

That said, it doesn't hurt to look at all. Little telescope time for a small chance of a huge payoff.





 
JadestarDate: Monday, 18.01.2016, 11:08 | Message # 23
Astronaut
Group: Users
United States
Messages: 70
Status: Offline
The mystery got stranger….

http://arxiv.org/pdf/1601.03256v1.pdf

The star has been dimming for over 100 years. Something you might expect if a megastructure was being constructed.

As noted in the paper linked above:

Quote
Tabby's Star, much discussed because of its mysterious periodic dimming, has a new oddity to show us. The observation records for this star, for the years 1890 to 1989 were gone over carefully. It was found that the star dimmed, in these 99 years, by a substantial 16 percent.

This sort of dimming is unprecedented in an F star, on the main sequence, as Tabby's Star is held to be.

Suppose we follow the favorite explanation for the dimming of this star, disrupted comets blocking its light. There would have to be an immense amount of dust over the course of a century. It would amount to the equivalent of about 648,000 giant comets, each crossing in front of the star, and each 200 kilometers (120 miles) in diameter. This would have to extend to our current observations, even though we see no signs of such dust.
Alternatively, we could be looking at a Dyson sphere, as it is being built, with 16 percent more light collected, and so blocked from our view, in the course of a century. Given the distance of this star, this would all really have been happening about 1500 years ago.


Edited by Jadestar - Monday, 18.01.2016, 11:12
 
parameciumkidDate: Monday, 18.01.2016, 19:32 | Message # 24
Explorer
Group: Users
United States
Messages: 277
Status: Offline
Oh good, someone finally named it. "KIC 8462852" was a mouthful, even if I did finally manage to memorize it (I think).




Intel HD Graphics 4000 ;P
 
DoctorOfSpaceDate: Monday, 18.01.2016, 20:05 | Message # 25
Galaxy Architect
Group: Global Moderators
Pirate
Messages: 3595
Status: Offline
Don't get your hopes up about aliens, that is the most unlikely scenario after Santa Claus' lost presents.




Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
JackDoleDate: Monday, 18.01.2016, 20:16 | Message # 26
Star Engineer
Group: Local Moderators
Germany
Messages: 1734
Status: Offline
Maybe it's a cloud of dark matter which moves in front of 'KIC 8462852'. The irregular fluctuations in the light curves would be caused by different density and distribution of the cloud.




Don't forget to look here.

 
WatsisnameDate: Monday, 18.01.2016, 20:41 | Message # 27
Galaxy Architect
Group: Global Moderators
United States
Messages: 2607
Status: Offline
Dark matter doesn't absorb light.




 
JackDoleDate: Monday, 18.01.2016, 20:45 | Message # 28
Star Engineer
Group: Local Moderators
Germany
Messages: 1734
Status: Offline
Quote Watsisname ()
Dark matter doesn't absorb light.

Maybe this is a still unknown type of dark matter? dry



Well, if anything light absorbed then it would probably also heat, so infrared radiation would be emitted. wink





Don't forget to look here.



Edited by JackDole - Monday, 18.01.2016, 21:14
 
DoctorOfSpaceDate: Monday, 18.01.2016, 21:44 | Message # 29
Galaxy Architect
Group: Global Moderators
Pirate
Messages: 3595
Status: Offline
Quote JackDole ()
Maybe this is a still unknown type of dark matter?


About as likely as aliens.





Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
WatsisnameDate: Monday, 18.01.2016, 22:16 | Message # 30
Galaxy Architect
Group: Global Moderators
United States
Messages: 2607
Status: Offline
Quote JackDole ()
Maybe this is a still unknown type of dark matter?


If it is, then we'd expect huge absorption of light over cosmological scales, and it would profoundly change the magnitude-redshift relation of galaxies.

I understand the temptation to invoke that mysterious thing we call 'dark matter' to explain any odd observation involving things looking dimmer than they should. But that is not what dark matter does, or what it was theorized for. Dark matter is particles that gravitate but are weakly interacting by electromagnetism. It must have this property, or else we would see it easily and the universe would look very different.





 
Forum » SpaceEngine » Science and Astronomy Discussions » Main Sequence Star Surrounded by Material Closely Orbiting (Normally only found around young stars)
Page 2 of 3«123»
Search: