Where are we actually looking for signals?


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Message boards : SETI@home Science : Where are we actually looking for signals?

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Cheopis
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Message 1007041 - Posted: 21 Jun 2010, 20:12:11 UTC

My impression is that we are basically riding on the coattails of whatever astronomy is being done at Arecibo.

Does that research also include occasional looks above or below the rotational plane of our galaxy?

If I were some sort of highly developed space civilization in the Milky Way and wanted to advertise my presence, if possible I would place emitters above or below the plane of rotation of the Milky Way. This would reduce interference, and reduce the required volume of space that one would need to transmit to. It would also reduce the possibility of literally intergalactic detection. A Galactic civilization might wish to not actively advertise it's presence to possible intergalactic civilizations, for all of the same reasons why some people believe we would be foolish to actively attempt to signal our presence more strongly than we do simply by existing.

My understanding is that there are a few stars out there above and below the disk that could be used for powering large emitters.

Has anyone looked at stars above or below the galactic disk?

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Message 1007096 - Posted: 21 Jun 2010, 23:12:20 UTC - in response to Message 1007041.

Hi Cheopis,
Your correct, SETI@home is just piggy-backing on the Arecibo telescope. They don't have any say in what the telescope is looking at.

I believe the Arecibo telescope has roughly about 70% sky coverage and astronomers use it for lots of different studies. So over the last 10 years, they have well covered the whole Arecibo field of view several times.

John.
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Message 1007151 - Posted: 22 Jun 2010, 3:24:41 UTC - in response to Message 1007041.

My impression is that we are basically riding on the coattails of whatever astronomy is being done at Arecibo.

Does that research also include occasional looks above or below the rotational plane of our galaxy?

If I were some sort of highly developed space civilization in the Milky Way and wanted to advertise my presence, if possible I would place emitters above or below the plane of rotation of the Milky Way. This would reduce interference, and reduce the required volume of space that one would need to transmit to. It would also reduce the possibility of literally intergalactic detection. A Galactic civilization might wish to not actively advertise it's presence to possible intergalactic civilizations, for all of the same reasons why some people believe we would be foolish to actively attempt to signal our presence more strongly than we do simply by existing.

My understanding is that there are a few stars out there above and below the disk that could be used for powering large emitters.

Has anyone looked at stars above or below the galactic disk?

Arecibo does see areas both above and below the plane of the Milky Way, because Earth's equatorial plane is significantly tilted relative to the galactic plane. The sky maps accessible from http://seticlassic.ssl.berkeley.edu/process_page/data_collection.html give a good idea of the specific regions. Arecibo sees about 31% of the full sky, though those maps use Cylindrical projection which makes the coverage appear less. There are two observing projects intending to cover all of the sky Arecibo sees using different observing strategies, so data from almost all that area will be processed by S@H.

There are also various other SETI searches. Quite a few are like S@H, just gathering data while other projects are controlling pointing. There have also been specific SETI controlled searches using various ideas on where and how best to look, though I don't know of any which specifically concentrate on looking above and below the galactic plane.
Joe

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Message 1009898 - Posted: 30 Jun 2010, 6:50:12 UTC

Thanks for the info, I wasn't aware of the coverage that Arecibo acually allows, or what parts of the galaxy that would equate to!

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Message 1010007 - Posted: 30 Jun 2010, 15:06:18 UTC - in response to Message 1009898.

I would assume that the new system that S@H is using would be looking further above and below where the telescope is being pointed at. I assume this because it would seem silly to have all 7 pointed in the same direction
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Message 1010087 - Posted: 30 Jun 2010, 20:36:55 UTC - in response to Message 1010007.

I would assume that the new system that S@H is using would be looking further above and below where the telescope is being pointed at. I assume this because it would seem silly to have all 7 pointed in the same direction

You're right, but since each of the 7 beams only covers 0.05 degrees the offset between beams is less than 3 times that. In addition, an observing project which uses the data from all 7 beams wouldn't want any of the beams losing too much sensitivity by using an area of the prime reflector dish too near the edge. In practice, survey projects will avoid the extremes of pointing. Perehaps only a project targeting a specific astronomical object would go really near the limits since the only alternative might be observing from some other radiotelescope.

The effects near the edges are complex, involving distortion of the beam shape, increased noise, less received signal, etc.
Joe

Message boards : SETI@home Science : Where are we actually looking for signals?

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