A report from China's FAST radio observatory, the world's largest by a substantial margin, says that a SETI signal candidate from the red dwarf star Kepler 438 may have been detected. Kepler 438 is known to have an Earth-sized exoplanet in it's habitable zone.

The narrow-band signal was reportedly found at 1140.6 MHZ. It was noted to be stronger in one polarization plane than the other, and to be drifting slightly in frequency.

Dr. Zhang Tongjie, head of the China Extraterrestrial Civlizations Research Group cautions that the signal could easily be caused by terrestrial interference . However, known sources of Earthly interference were ruled out by carefully noting the signal's characteristics.

A differing opinion was given by Dr. Bo Peng, supervisor of operations at the FAST Telescope. He stated his conviction that the signal is 'likely' of extraterrestrial, intelligent origin.

Mmmm...

Not wishing to be downcast but...

They do have a lot of tourists visit there... All with mobile phones and whatever i-thingies...


Keep searchin'!
Martin

---

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The signal was detected in only one of the FASTtelescope's 19 directional beams, the one facing Kepler 438. It was also drifting at a rate like that which would be caused by the rotation or stellar orbiting of an exoplanet. These facts were used to rule out ground-based sources of interference.

The signal persisted for the 20 minute length of the observing session. This was used to rule out interference from aircraft, and satellites, which would have moved out of one beam and into another, in that time.

Then, too, after all the trouble the Chinese went to, to build this huge instrument, its hard to believe that they wouldn't have set up a radio quiet zone, to avoid such interference. The Greenbank radio astronomy observatory, in West Virginia, USA, for example, is rather famous for its extensive radio quite zone.

One had to laugh at Hollywood a bit, when they had Jodie Foster, in the movie 'Contact', issuing commands by mobile phone, from the field right under the VLA telescope dishes, as she sped back to the control room.

BLC-1 was another 'technosignature' that held our attention. However, closer examination ruled it out https://www.nature.com/articles/s41550-021-01508-8.
Let's hope this one from FAST is the real deal.

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The concerns about a complex radio frequency intermodulation environment, expressed in the Nature article, in relation to the BLC-1 signal, are well taken. The same sort of detective work is presumably being undertaken now, at the FAST observatory, with respect to the Kepler 438 signal.

I've read the scientific paper from the FAST team. I found the waterfall display of particular interest. It reveals a slightly sloping, nearly vertical line (figure 4, page 12) denoting a signal slowly drifting in frequency. It appears in only one of the 19 directional beams.

The paper maintains that this tends to argue against the effects of instrumental artifacts, like oscillator harmonics, from FAST itself. The paper also notes that the frequency of the signal bears no relation to the fundamental frequencies of the local oscillators at FAST.

I noted in the waterfall display, that the downward frequency drift of the signal begins at a faster rate, then gradually shifts to a slower rate. This could be caused by a transmitter on a rotating planet that is moving away from the receiver at a gradually diminishing angle.

A link to the referenced paper may be found, below:

https://assets.researchsquare.com/files/rs-1335086/v1_covered.pdf?c=1645546954

https://www.youtube.com/watch?v=x67K-Vq1KWk&t=884s

Here another opinion for only being rejected or discarded.

If the Kepler 438 signal turns out to be a real SETI 'hit', a natural assumption would be that it comes from the star's one known planet, Kepler 438b. Interestingly, this planet just happens to be the most Earth-like exoplanet known, at least on the basis of its diameter, and the fact that it resides near the inner edge of its star's habitable zone.

Unfortunately, Kepler 438 is a flare star. It outbursts could erode any atmosphere of a nearby planet, spoiling the chances for life. Since 438b is so near its star, it is likely tidally locked, always presenting the same side to it. Such slow rotation would work against the creation of a strong planetary magnetic field, which might otherwise protect the planet's atmosphere from stellar erosion.

Perhaps the signal comes from another, nearer source, which happens to lie along a line from Earth to Kepler 438. Since Kepler 438 lies some 473 light years away, there would be ample room for another star, or some other transmitting object, to happen to fall along the same line of sight.

https://www.youtube.com/watch?v=x67K-Vq1KWk&t=884s

Here another opinion for only being rejected or discarded.

The Wow Signal was and is a perfectly respectable SETI candidate signal. However, until it's received again, it must remain just that, a candidate signal-- a possible instance of extraterrestrial intelligence, not an actuality.

We can't authenticate what we can't examine in great detail, far greater detail than that provided by the records of the 'Big Ear' radio telescope. Granted, it may be a 'one shot' signal sent out by some far- off civilization, much as was done from the now-defunct Arecibo radio telescope, some years ago, but we can't really know that, as yet.

One sidelight that may be of interest-- its often said that the Wow Signal was recorded in such a way that no modulation, assuming any was present, could be discerned. That's mostly true, except . . .

I just realized something, while looking again at the famous Wow Signal computer readout. To the right of the coded sequence: 6 E Q U J 5, there are a couple of high level outliers, 70 and 140 KiloHertz higher in frequency.

These features are labeled 6 and 7, and occur in the same time bins as the 'Q' and 'U', respectively. It's perfectly possible that these are traces of frequency modulation. They occur when the signal was at its strongest, when it was in the highest gain part of the telescope's directional beam.

So is power the same as any signal strength, or did they forget hanging up after finishing transmitting?

The alphanumeric code used for the Wow Signal signifies standard deviations from constant background levels of radio noise. Zero is a blank space. Numerals 1 through 9 are obvious. A is 10 to 11 sigma. B is 11 to 12 sigma, and so on.

The lowest numerals are presumably sporadic random noise, above the noise floor. The signal was no longer detected after 6 time bins, or about 37 seconds. This is when a point source would have exited the directional beam of the telescope.

Below, please find a link to an image of the Wow Signal computer printout:

https://briankoberlein.com/post/wow

Is not the best 'guess' for identifying the "Wow!" signal that it was from the ionization [hydrogen] trail of a [nearby] comet burning up in our atmosphere?...


The receiver aerial was actually two aerials that swept their angle of view across the sky delayed by a few degrees... A real "Wow!" signal would be seen by both aerials. Except in this case, the "Wow!" signal was too fleeting a brief phenomena...

However, such a fleeting 'one-off' pulse is exactly what would be expected from a terrestrial [nearby] comet...


Keep searchin'!
Martin

[edit]Corrections[/edit]

---

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Take a look for yourself: Linux Format
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Comets are weak emitters, at best, at the hydrogen line. This was the frequency range monitored by the OSU 'Big Ear' telescope. A comet being destroyed within Earth's atmosphere, large enough to produce a substantial emission, should have been obvious at the time. I have never heard of this particular scenario being scientifically proposed as an explanation for the Wow Signal.

The Wow Signal did not happen to persist long enough to be received by both of the telescope's directional beams. Assuming that it was a real SETI signal, we have no way of saying how long it should have lasted, or why it might have been turned off when it was. Perhaps whoever sent the signal simply 'signed off' at that point.

The famous signal sent out by the Arecibo Observatory to the star cluster M13 lasted only short time, and was not repeated. If the rotation of some exoplanet happened to sweep the beam of a fixed radio telescope past Earth's position in space, it could easily have done so during the last few tens of seconds of the complete transmission. The result would be the same as what was experienced at the 'Big Ear'.

See:

Alien ‘Wow!’ signal could be explained after almost 40 years
wrote:

... He didn’t find aliens but he did find two suspicious looking comets.

Known as 266P/Christensen and 335P/Gibbs, they have never been investigated before because they were only discovered in 2006 and 2008 respectively. Paris found that they were both in the vicinity of Chi Sagittarii on the day that the ‘Wow!’ signal was detected.

This could be significant because comets are surrounded by clouds of hydrogen gas that are millions of kilometres in diameter. The ‘Wow!’ signal itself was detected by Ehman at 1420MHz, which is a radio frequency that hydrogen naturally emits...

Wow! signal explained after 40 years?
wrote:

... two comets, 266P/Christensen and P/2008 Y2 (Gibbs), were passing through the part of the sky the Big Ear Radio Observatory was surveying in 1977, when the Wow! signal was noticed. These astronomers believe the signal came from a hydrogen cloud accompanying one or the other comet. This idea would explain why the Wow! signal was not measured again: the comet that caused it moved on in its orbit.

Paris and team recently took an opportunity to survey the region of the sky around Sagittarius once again, using a 10-meter radio telescope, when Comet 266P/Christensen was again passing through this region. They determined that the signal of 266P/Christensen (and three other comets) matched the Wow! signal...

Keep searchin'!
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Prof. Paris specified a comet in open space, not one burning up in Earth's atmosphere. It would have had the slow apparent motion of such a comet, and would have been easily seen in both of the Big Ear's directional beams over a period of several minutes. It wasn't.

Please find a linked article below that goes further into the reasons that most scientists were not enthusiastic about Prof. Paris' explanation for the Wow Signal.

https://www.livescience.com/59442-astronomers-skeptical-about-wow-signal.html

Thanks for that, and there are good comments in that article.

... Including that the comet (and associated hydrogen tail) could well have only impinged on. for example, the tip of only one of the receiving lobes.


Despite looking further, nothing more has been heard since. So, certainly no beacon!

Meanwhile, there is good research for just trying some listening!!


Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

One astronomer has commented on 'suspicious' signals received by the FAST Observatory, well before the much-discussed Kepler 438 signal. He judges that they are of Earthly origin. His main reason for thinking so appears to be that each signal could be heard when the telescope was pointing in various directions.

This is a classic 'off-axis' test for a candidate SETI signal. A true signal from space should disappear when the telescope's aim is changed. An interfering signal from Earth will probably be heard at various different aimings. All well and good, so far.

However, these earlier signals seem to have become confused, by some news sources, with the later Kepler 438 signal. It was reportedly heard only when one of the 19 directional beams of the FAST instrument was pointed directly at it, and at no other time.

The blanket statement about the earlier signals being Earthly is origin appears to have been stretched out of all proportion to make it apply to the Kepler 438 signal, too. This probably happened because the reception of the earlier signals, and the later Kepler 438 signal were announced at the the same time.

The principal reason for suspecting that the Kepler 438 signal is really radio interference within the equipment of the FAST Telescope is given in the discovery paper. The reason is that the signal is notably stronger in one polarization domain than the other. This caused the observers to suspect that a harmonic of one of their local oscillators was the source of the signal. Experience had shown them that such interference had such power differences.

It is admitted, though, that no such harmonic falls at or near the observed frequency of the Kepler 438 signal. One can do the math and prove this for themselves. The local oscillator frequencies of FAST are:
33.333 MegaHertz and 125.000 MegaHertz. The frequency of the Kepler 438 signal is 1140. 604 MegaHertz. The closest oscillator harmonics are 1133.33 MHz, 1166.66 MHz, 1125.00 Mhz and 1250.00 MHz. Given the 1Hz discrimination of the receiver, none of these appear relevant.

I wondered if a mixing product of the two oscillators could be responsible. This would exist as the sum of one the harmonics of oscillator A , plus a harmonic of oscillator B. Alternately, a mixing product could be the frequency difference of a harmonic of oscillator A and one from oscillator B. I checked these possibilities, but, assuming my math is correct, no obvious mixing products appear to match the frequency of the Kepler 438 signal.

The power discrepancy in the signal, in different polarities, could be caused by something as simple as a linearly polarized signal that happened to match the polarization angle of one of the antenna elements reasonably well.

There are certain so-called 'magic frequencies' discussed in SETI circles. The most obvious of these is the transition frequency of neutral hydrogen, at 1420.405 MHz. There are several emission lines of Hydroxyl (HO) between 1612 and 1720.5MHz.

The band between the hydrogen and hydroxyl frequencies constitutes the well known 'waterhole'. It seems a logical place for senders and receivers of SETI signals to concentrate their efforts. This band has the added benefit of being in the area of the spectrum with a minimum of atmospheric absorption of radio waves, and noise.

This band of radio frequencies has been widely monitored, without conclusive result. A number of other magic frequencies have been proposed. Some may remember 'hydrogen times Pi' from the motion picture Contact. This sort of interplay between math constants and small integers and radio emission lines is typical of much of the thinking about magic frequencies.

I was interested to see if the frequency of the Kepler 438 signal would fall at or near any of the existing magic frequencies, or any new ones that might reasonably be devised. None, so far is wholly convincing; the search is ongoing.

One can at least observe that the Kepler 438 signal falls near enough the waterhole to share in most of its low absorption, low noise advantages, where interstellar communications is concerned.

Addendum to the above.: I just found a reasonably good match in the square root of two. This is also known as Pythagoras' constant. Numerically it is 1.4142. Geometrically it is the length of the diagonal of a square with one-unit-long sides. It is related to the more familiar Pythagorean Theorem.

1.4142 times the frequency of the Kepler 438 signal -- 1140.604 MHz, very nearly equals the lowest frequency hydroxyl emission line -- 1612.231 MHz. The discrepancy is only about 1 part in 2000. The figure obtained being 1613.042 MHz.

A report from China's FAST radio observatory, the world's largest by a substantial margin, says that a SETI signal candidate from the red dwarf star Kepler 438 may have been detected. Kepler 438 is known to have an Earth-sized exoplanet in it's habitable zone.

The narrow-band signal was reportedly found at 1140.6 MHZ. It was noted to be stronger in one polarization plane than the other, and to be drifting slightly in frequency.

Dr. Zhang Tongjie, head of the China Extraterrestrial Civlizations Research Group cautions that the signal could easily be caused by terrestrial interference . However, known sources of Earthly interference were ruled out by carefully noting the signal's characteristics.

A differing opinion was given by Dr. Bo Peng, supervisor of operations at the FAST Telescope. He stated his conviction that the signal is 'likely' of extraterrestrial, intelligent origin.

By way of substantiating the account of Dr. Bo Peng's remark, above, I give a link to an article on this. Its original source was 'Science and Technology Daily', a Chinese government newspaper.

Dr. Peng , besides being the overseer of operations at FAST, is a member of the Chinese Academy of Sciences, Key Laboratory of FAST, and the National Astronomical Observatories of China. Dr. Peng's remark appears in the final paragraph of the article.

https://futurism.com/chinese-scientists-extraterrestrial-intelligence-dubious

Does the power of a signal diminish only because it could be finishing?