Candidate: 920891 (RA: 2.645508 Dec: 26.547533)


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Message 930681 - Posted: 3 Sep 2009, 20:54:09 UTC
Last modified: 3 Sep 2009, 20:54:09 UTC

This is a discussion thread for SETI@home candidate # 920891 (located at RA: 2.645508 Dec: 26.547533)
Please feel to exchange thoughts, comments, questions and answers regarding this particular candidate.
For more information, please read the NTPCkr Frequently Asked Questions (FAQ).

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Message 938455 - Posted: 8 Oct 2009, 22:31:46 UTC

Now that the NTPCkr also shows pixel-boundaries (when you zoom in), it is easier to see that candidate 920891 includes a relatively bright star of magnitude 9.3 or so. I think this star is "TYC 1775-1429-1" (from the Tycho-2 catalogue), but it does not have a corresponding Hipparcos entry; Can anybody make an educated guess about the distance to this K0-type star?

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Message 938602 - Posted: 9 Oct 2009, 10:41:13 UTC

Well, good question.

I would be nice to get some discuss with the scientists here. They can explain, how far is the distance, what shows the graphics, etc.


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Message 938809 - Posted: 10 Oct 2009, 1:00:21 UTC
Last modified: 10 Oct 2009, 1:18:07 UTC

It seem there are two objects at this position:

Cat: DSLN DSL DSL HIP GVC BSC SKY TY2 SAC

- 2h38m43.71s +26°32'05.5" * SAO 75492 BD+25 431 mV: 9.33 B-V: 1.20 sp:K0 pm: 0.018 -0.016
- 2h38m43.71s +26°32'05.5" * TYC1775-01429-1 Bt:10.94 Vt: 9.44 mV: 9.30 b-v: 1.28 pm: 0.013 -0.019

Ce champ contient 2 objets

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Message 938928 - Posted: 10 Oct 2009, 5:53:49 UTC - in response to Message 938809.

Well, I believe "SAO 75492" and "BD+25 431" are actually just alternative identifiers from other catalogues for TYC 1775-1429-1. SIMBAD also lists these additional identifiers for the same object: AG+26 260, GSC 01775-01429, PPM 91859, YZ 26 1395 and 2MASS J02384371+2632055. And according to the "proximity indicator" value of "999" in the Tycho-2 Catalogue, there doesn't seem to be other objects that are very close to it.
Check out...
http://simbad.u-strasbg.fr/simbad/sim-id?Ident=TYC+1775-1429-1&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id
and
http://vizier.u-strasbg.fr/viz-bin/VizieR-S?TYC%201775-1429-1

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Message 938960 - Posted: 10 Oct 2009, 12:07:11 UTC
Last modified: 10 Oct 2009, 12:16:57 UTC

Here is another picture of it from the digital sky survey;



And another one;



The SIMBAD query is here.

The stars in the image are in several sky surveys.

John.
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Message 939037 - Posted: 10 Oct 2009, 19:19:08 UTC - in response to Message 938960.

John, your SIMBAD query is for a large radius of 10 arcmin (or a 20 arcmin diameter), while the widths of your images are only about 4 arcmin across (and SETI's telescope "beam" has a radius of only about 3 arcmin, I think). Apart from the BD+25 431 result of your query (which is an alternative ID of TYC 1775-1429-1), the other three results (1RXS J023835.5+262530, TYC 1775-890-1 and 2MASX J02384524+2641201) are not for any objects in your images but are actually several NTPCkr pixels away. Regarding the Tycho-2 catalogue's proximity indicator value of 999, this just tells us that the Hipparcos satellite did not detect other objects within a radius of 99.9 arcsec (or 1.665 arcmin) from TYC 1775-1429-1. Obviously we can see more objects in those images than Hipparcos/Tycho-2, and several sky surveys have catalogued them, yes, as is evident from other queries through VizieR. However, among the 62 catalogues that VizieR queries around the coordinates of TYC 1775-1429-1, only one catalogue (I/154/ac1950) returns two results that are extremely close to that location (within 2.6 arcsec, which are likely duplicate entries, given the apparent diameter of TYC 1775-1429-1 and the knowledge that I/154/ac1950 was compiled from "photographic plates taken by the normal astrographs which are installed in observatories"). For all of the other 11 or so catalogues that return multiple entries around that location, the second entry is at least about 13 arcsec away, which I think is that blue/purple dot (almost) touching the big orange blob on its left side. So I still think the big orange blob at the location of TYC 1775-1429-1 is just one star, and it is that star's distance I am asking about.

But, of course, this forum thread is about pixel # 920891 as a candidate in general, and the discussions can also include some of the other objects like the ones immediately to the left and right of TYC 1775-1429-1, or, I would presume, even about objects within 3 to 6 arcmin or so outside the indicated pixel region, which should cover most of the possible detection errors that SETI might make.

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Message 939171 - Posted: 11 Oct 2009, 14:57:09 UTC - in response to Message 938455.
Last modified: 11 Oct 2009, 15:51:19 UTC

@Tiaan
I'm not an astronomer, but a Google search came up with two articles that, together, might permit an estimate of the distance to this star.

1) The astronomy lecture notes on magnitude-distance, by Hans Krimm http://ceres.hsc.edu/homepages/classes/astronomy/spring99/Mathematics/sec19.html
state that the distance to a star can be calculated from a knowledge of its absolute magnitude (M) and its apparent magnitude (m).

The equation is: distance in parsecs = 10^((m-M +5)/5)


2) In the paper by Martin, E.G. (1945) "The absolute magnitudes of the stars of type K0" The Observatory, Vol. 66, p. 82-87.
http://articles.adsabs.harvard.edu//full/1945Obs....66...82M/0000087.000.html
Table III shows the absolute magnitudes of several K0 type stars. The spectroscopic values are surprisingly reproducible, with an average absolute magnitude of 2.3

3) From what I can understand of the stellar catalog codes for this star, it has an apparent magnitude (Bt) of 10.94

4) Putting all of this together:
(10.94-2.3+5)/5 = 2.728
10^2.728 = 534.56 parsecs = 1744 light years.

I have no idea if this is correct.
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Message 939200 - Posted: 11 Oct 2009, 18:09:53 UTC - in response to Message 939171.

@Jon: Thanks for giving it a try. I also don't know if the answer is correct, but I suspect your estimate might be on the low end. However, I think the method you're referring to is the right one to be used: calculating a "spectroscopic distance" for the star. To get a better estimate of the absolute magnitude, one would probably need to figure out what "luminosity class" the star is classified under (such as Ia, Ib, II, III, IV or V; someone might even be able to measure this). This classification could make a really big difference to the distance estimate. I doubt that TYC 1775-1429-1 would be a main-sequence star (class V), or else it would have been close enough for a parallax distance to be known; I suspect it is more likely to be one of the giant-type classes. Also, regarding the apparent magnitude, I am not sure if one should use the Johnson visual magnitude of 9.3, the V-band magnitude of 9.4, or the B-band of about 10.9 (the one you used), but this choice would roughly only double (or half) the estimate. Using your formula, if the star is a class-III giant with an absolute magnitude of about 0, then the distance could be around 3000 light-years. If it is a class-Ia supergiant with an absolute magnitude of about -7, the distance could even be 200000 light-years. But I am also not an astronomer, just find this stuff interesting. :)

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Message 939215 - Posted: 11 Oct 2009, 18:59:21 UTC - in response to Message 939200.

I also find this fascinating.
Many thanks for all the additional stellar-type info, which certainly increases the probable distance to this star.
However, although this is the first example the NTPCKr has produced of a candidate with a star in the field of view, the pulse data looks like RFI. I have no comment about the Gaussian, spike, and triplet data, which (without further analysis) may be "real". Nevertheless, it's interesting to consider just how powerful any transmitter would have to be for us to pick it up at over 1700 light years! I guess it could have been deliberately broadcast at us, if the sender had realised that our atmosphere signature indicated life (just as we're planning to do with the upcoming generation of space telescopes). Even so, it would have to be one heck of a transmitter.

Off topic: it would be really useful if the waterfall plots were colour-coded according to signal strength, as they are in the old newsletter about waterfall plots http://setiathome.berkeley.edu/sah_sci_newsletters.php?frag=news-6.inc
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Message 939249 - Posted: 11 Oct 2009, 22:18:23 UTC - in response to Message 939215.

@Jon: Yes, determining the origin of a signal is probably much more difficult than estimating distances to stars. And whether it would be wise for us as humans, with a civilization that is extremely young in terms of cosmological timeframes, to broadcast our existence to potentially hostile and super-advanced extraterrestrials (if any exist), is a philosophical debate for another forum. Perhaps we should first work on a unified global civilization and then let the citizens of the world have a referendum on that one. :)

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Message 939689 - Posted: 14 Oct 2009, 1:46:55 UTC - in response to Message 939215.
Last modified: 14 Oct 2009, 2:12:42 UTC

I guess it could have been deliberately broadcast at us, if the sender had realised that our atmosphere signature indicated life (just as we're planning to do with the upcoming generation of space telescopes). Even so, it would have to be one heck of a transmitter.

Thats a really good point there Jon!

As you say, after the Kepler telescope detects planets, next we will be looking closer to look for signatures of life. If ET's have been doing this, and thousands of years ago they detected atmospheric signatures of Life around our Sun, maybe they transmitted some directional signal or beacon in our direction. Its one possible scenario, maybe they detected biological life signatures and just transmitted an;
"Hello, we're here guys. If your an advanced civilisation, say hello back!".

Remember that if Einstein was correct, and the speed of light is the definitive universal speed limiter, then we can never travel hugh distances across space. So transmitting "hello" signals would be safe as we could never meet the Alien's in person. We could only ever send messages back and forth with the massive "distance/light years" time lag between messages.

John.
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Message 939776 - Posted: 14 Oct 2009, 8:26:04 UTC - in response to Message 939689.

Hi John & Tiaan

In answer to my own question, this link http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html
was posted in another thread and indicates the detection distance limits for various frequency ranges and types of signal.
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Message 939849 - Posted: 14 Oct 2009, 15:21:55 UTC - in response to Message 939776.

Nice link, Jon -- very detailed analysis. So it seems that detecting any signal from beyond 1000 light-years is very unlikely, which also gives some credibility to the zero value in the star-count column of NTPCkr for this candidate. (Goodbye, TYC 1775-1429-1.) Anyway, I think NTPCkr provides a great learn-through-example experience, and hopefully it would get unstuck from the top-10-candidates-as-of-3-September-2009 state soon (wonder what's up with that).

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Message 939856 - Posted: 14 Oct 2009, 15:48:26 UTC - in response to Message 939849.

Hi Tiaan

From Matt's posts, it seems that the database takes quite a pounding each time they run the NTPCKr. So, I don't expect an updated candidate list until things have calmed down with the current server problems. Also, Eric was apparently testing some RFI rejection software, so maybe they want to combine that with the NTPCKr to make the next run more meaningful.
According to that calculation page, it seems that a 120 terawatt transmission (2.3Ghz, 0.1Hz bandwidth) from 1700 Lyr away, could be detected by Aricebo. No idea how feasible that technology would be.
Anyway, we're pretty much all decided that this one is just random noise.
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Message 940740 - Posted: 17 Oct 2009, 10:40:46 UTC
Last modified: 17 Oct 2009, 10:47:01 UTC

Guys there is one thing we are learning about nitpicker, its a very valuable tool that is only going to get better as time goes on. Anyone that has posted to this thread has been following SETI@home for several years and knows that science takes time. Matt and the guys are working very hard on this thing, its going to be an incredible tool in the coming months.

This is science, this is what brought all of us here in the first place. Its great to be able to see this incredible science progress in the making.

John.
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Message 940767 - Posted: 17 Oct 2009, 13:21:19 UTC - in response to Message 940740.

Guys there is one thing we are learning about nitpicker, its a very valuable tool that is only going to get better as time goes on. Anyone that has posted to this thread has been following SETI@home for several years and knows that science takes time. Matt and the guys are working very hard on this thing, its going to be an incredible tool in the coming months.

This is science, this is what brought all of us here in the first place. Its great to be able to see this incredible science progress in the making.

John.



Well said Johnney.
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Message 941009 - Posted: 18 Oct 2009, 4:17:28 UTC - in response to Message 939856.

Hi Tiaan

From Matt's posts, it seems that the database takes quite a pounding each time they run the NTPCKr. So, I don't expect an updated candidate list until things have calmed down with the current server problems. Also, Eric was apparently testing some RFI rejection software, so maybe they want to combine that with the NTPCKr to make the next run more meaningful.
According to that calculation page, it seems that a 120 terawatt transmission (2.3Ghz, 0.1Hz bandwidth) from 1700 Lyr away, could be detected by Aricebo. No idea how feasible that technology would be.
Anyway, we're pretty much all decided that this one is just random noise.

And that is the issue. We don't seem to have a spare 120 terawatts to send out a signal beacon. How does that fit into the Drake equation? It could be the galaxy is teeming but no one has the spare power for a 24/7 signal beacon. Rather depressing thought.

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Message 941049 - Posted: 18 Oct 2009, 8:45:43 UTC - in response to Message 941009.

For a really advanced civilization, 120 terawatts may not be a big deal: remember that E=m.c^2, so it is only slightly more than one single gram of stuff per second you need to turn into pure energy. For all we know there might be one of these generators in every efficient time-space folding machine that might allow "faster than light" travel. Given a few more decades, centuries or millennia, even mere humans might be able to do it. Think big -- no rush, and stick to listening for now... :)

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Message 941050 - Posted: 18 Oct 2009, 8:52:39 UTC - in response to Message 941009.
Last modified: 18 Oct 2009, 9:20:06 UTC

Agreed!
One popular idea out there on the message boards is that SETI will pick up signals from a civilisation just going about its normal business - we'll be eavesdropping on their TV, radio, or radar.

However, using our own TV/Radio/radar transmissions as a guide (see http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html), human transmissions could not be detected with an Aricebo-sized dish at a light year distance. So, we're only likely to "eavesdrop" on ET if their civilisation extends over a few planets/solar systems - something that might require them to increase the power of their transmissions above that for "standard" terrestrial point-to-point communication.
It seems more likely that any signal we pick up will have been deliberately pointed at us (possibly on the basis of a "life" signature in our atmosphere). No-one knows how aliens think, but humans certainly wouldn't spend years and years blasting a (very expensive) signal towards a planet that may or may not harbour a life-form that could receive it.

[edit]
BTW, I'm not saying we shouldn't be looking for these signals - Quite the opposite. We ought to be using a receiver that could detect much weaker transmissions (e.g. an antenna size that could detect our own radio transmissions at over 10 Lyr).
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