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Fraser
2005-Apr-11, 06:29 PM
SUMMARY: Since the beginning of astronomical observation, science has been viewing light on a curve. In a galaxy filled with thousands of eclipsing binary stars, we've refined our skills by measuring the brightness or intensity of so-called variable star as a function of time. The result is known as a "light curve". Through this type of study, we've discovered size, distance and orbital speed of stellar bodies and refined our ability to detect planetary bodies orbiting distant suns. Here on Earth, most of the time it's impossible for us to resolve such small objects even with the most powerful of telescopes, because their size is less than one pixel in the detector. But new research should let us determine the shape of an object... like a ringed planet, or an orbiting alien space station.

View full article (http://www.universetoday.com/am/publish/alien_space_stations.html)

What do you think about this story? Post your comments below.

piersdad
2005-Apr-11, 07:38 PM
planets and how to find them.
they are really getting down to the nitty gritty with analyising single pixels for artificial variations.


As Luc points out, this type of research may well be within the realm of the contributing amateur astronomer. Currently the search for signs of extra-terrestrial intelligence are limited to radio and the search for laser pulse which demands specialized equipment. "For the moment, there is no project to apply this idea. If it the idea turns into a specific (SETI) observing program, a number of collaborations would be welcome!"


A collection of artificial bodies would produce light curves easily distinguishable from natural ones.

so i wait with bated breath for the next bright idea from the boffins

The Near-Sighted Astronomer
2005-Apr-11, 07:53 PM
Two things come to mind...

First: Detecting an irregularly shaped highly-absorptive object is most likely to occur as it enters or exits the limb of a star - while in transit across a point source of light shape would have little influence.

Second, very large structures of this type are more likely to be developed primarily as solar-energy collectors. In this case a materially-endowed techno-advanced, but energy-limited culture might place such humongous structures in space for reasons other than as a means to signal line-of-sight planetary systems of their presence in the scheme of things...

I applaud Luc's pluck in developing this idea BUT i would say that should such devices exist AND have irregular shapes, they would probably be discovered during routine sweeps for transiting planets and flagged once their peculiariarities in shape were noted in the course of followup.

lswinford
2005-Apr-11, 08:20 PM
shhh...secret message obtained..."Agent X33 on Earth to Zorkon high command: application of new technology leads me to recommend that orbiting fortresses and observation posts be converted to spherical shape, our pyramid structures may be detectable soon"

Don't tell anyone.

PS: to Fraser, thanks for the article.

antoniseb
2005-Apr-11, 08:26 PM
This was an entertaining article. It's fun to think about detecting aliens who are doing really big obvious things.

Don Alexander
2005-Apr-11, 10:09 PM
One should think that an alien civilization capable of constructing artifacts large enough to be detectable when transiting their host star (approximately a Type 1.5 civilization on the Kardashev scale) would also pour out so much electromagnetic noise that we could detect them from thousands of light years away, even if they are not trying to communicate directly.

Furthermore, I have a problem with this sentence:
"Since they would always pass in front of their parent star for a given remote observer..."
A transit is only visible if we are viewing the system edge-on, so, to actually signal in all directions, a lot of satellites in orbits from equatorial to polar must be implemented (the density could be reduced toward the Galactic poles).


First: Detecting an irregularly shaped highly-absorptive object is most likely to occur as it enters or exits the limb of a star - while in transit across a point source of light shape would have little influence.

Viewed from the alien artifact itself, the star will have a visible disk, of course. The transit we observe is resolved in time, but not in space.

But the idea of solar power stations is a good one, though not original, of course.

David Alexander Kann
Thueringer Landessternwarte Tautenburg

PS.: If this interests you, check out Dyson spheres.

wstevenbrown
2005-Apr-12, 12:24 AM
Ringworld signature = TEST PATTERN. :P S

mcsejung
2005-Apr-12, 12:52 PM
Wouldn't sun-spots on those distant stars cause false positives?

antoniseb
2005-Apr-12, 03:38 PM
Originally posted by mcsejung@Apr 12 2005, 12:52 PM
Wouldn't sun-spots on those distant stars cause false positives?
They would have to be very large unusually shaped sunspots. The idea is that these objects are far from round, and have some very regular shape, leading to some strange dimming curves.

antoniseb
2005-Apr-12, 08:26 PM
There is a New Scientist Article:
Look out for giant triangles in space
12 April 2005
Exclusive from New Scientist Print Edition
Marcus Chown
http://www.newscientist.com/article.ns?id=...=mg18624944.800 (http://www.newscientist.com/article.ns?id=mg18624944.800)

I wonder where they go the idea?

wstevenbrown
2005-Apr-14, 05:33 AM
They would have to be very large unusually shaped sunspots.

Large and unusual starspots do exist. They are routinely tracked in stars of the Chi Lupi type, and in FG Sagittae stars, mercury-manganese stars, and so forth. These stars are typically spectral type Am or Fm, where the m designates apparent extreme metal enhancement. Also typically, they are slow-rotating, non-convective stars. Rare metals and high atomic weight metals are enhanced in the spectrum showing apparent abundances thousands to millions of times solar. I say apparent, because, IMHO, the combination of light pressure and surface magnetic field of the star has 'combed' these elements to the surface and segregated them into the photosphere of the star, where they are disproportianately represented in the absorption spectrum. The elements selectively enhanced are typically the ones having the most extreme properties magnetically-- especially if one looks at the particular rare earths of the Lanthanide series that are enhanced.

The devilish thing about these is that they are very difficult to study, for several reasons (The spots themselves are very durable, apparently lasting for decades and centuries.) First, rotation period varies with latitude, and the spots shift in latitude also, while maintaining their integrity. Second, as The Nearsighted Astronomer has noted, limb effects come into play. For the uninitiate, limb darkening is a whole grab-bag of effects which happen when you try to examine a light-emitting sphere with an atmosphere = star. The nearer the limb (edge) of the star, the more atmosphere you must look through to see the light-emitting region. This makes observations near the limb depend sensitively on the model of the star's atmosphere. Just try to find consensus on the atmospheric composition/structure of these unusual objects!

I had a point here somewhere, now what did I do with it? Oh, yeah. When the starspots rotate out of view, their spectral contribution, which is different from that of the star as a whole, disappears. The spectrum itself alters, as the high-metal contribution disappears. This is what will distinguish starspots from opaque transiting objects, which only change the intensity (across the entire spectrum) of the light curve. This, and the fact that starspots migrate in latitude, which changes their apparent rotation period. An orbiting opaque object cannot simulate this.

The poor guy has got his work cut out for him. Steve

GOURDHEAD
2005-Apr-14, 07:16 PM
This, and the fact that starspots migrate in latitude, which changes their apparent rotation period. An orbiting opaque object cannot simulate this. Ah-h-h! but an orbiting opaque object under the control of technologically competent critters could move in this and other distinguishable ways.

wstevenbrown
2005-Apr-14, 08:21 PM
Powered orbits are only legal for Type II and above civilizations. See Galactic Code Article 314159. :P S

Guest
2005-Apr-16, 12:56 PM
I have made some images ov various plausible megastructures using Celestia to show the kinds of signatures that might be visable from far away;

Dyson Statites; lightweight structures supported against gravity by
light pressure, collecting solar energy for conversion into stored and
beamed energy...
http://tinypic.com/4huo0p

a Dyson Swarm, a collection of independently orbiting elements which collect as much starlight as possible; as Freeman Dyson himself pointed out, the most easily detectable signature of such a swarm might be the infrared waste heat surrounding the star in a halo (although there would be some dimming of the central star as well)...
http://tinypic.com/4huo8j

a Bishop ring , a structure made from Carbon bucky fibre several thousand kilometers across (any bigger and the structure would rip itself apart by centrifugal force)
http://tinypic.com/4huo9y

any such structures should be detectable in the near future if any
advanced civilisation exists any where in the galaxy; conversely, any
distant civilisation would be able to see us if and when we build such
structures.

eburacum45
2005-Apr-16, 03:43 PM
Logs in to claim previous post...

Sean McCrohan
2005-Apr-19, 02:31 AM
I beleive that aliens are aggressive in nature and that they have visited Earth nad are seeing wether we are woth destroy :blink: ing

Fraser
2005-Apr-19, 03:48 PM
Very cool pictures eburacum45. Celestica is an amazing program. We should have a Celestica contest...