Detected Radio Signal from Proxima Centauri:
If there is one thing that we've learnt during these days is that
astronomers are not able to keep secrets. In fact, news of an enigmatic radio signal
from the direction of Proxima Centauri, the Sun's nearest stellar neighbour,
is plastering the headlines. The discovery was leaked to
the British newspaper The Guardian, which reported the story December 18.
Researchers subsequently granted interviews to Scientific American and National Geographic.
Since then, however, the discovery team has remained tight-lipped about the signal.
Have we just detected a radio communication from aliens?
Well, I really wish we had: unfortunately, there are some clues that it might be a radio signal
this will help us to take stock of the situation.
The Proxima Centauri radio signal detection recalls the “Wow!” signal detection: on august 15,
1977, the Big Ear Radio Telescope in Delaware, Ohio, received the most powerful signal it would
ever detect during its decades of observations. The signal lasted just 72 seconds,
but when an astronomer spotted it on a computer printout days later,
he was so impressed that he quickly scrawled “Wow!” in red pen across the page. The data
looked much like what SETI astronomers expected to see from an alien intelligence. However,
despite many attempts to follow up on the find, the so-called “Wow! Signal” has never reappeared.
“Was that E.T. or was it not E.T.? Nobody knows,” Seth Shostak, said senior astronomer
at the SETI Institute “Nobody has ever found another explanation for what that might have
been. It's like you hear chains rattling in your attic and you think ‘My god ghosts are real.’
But then you never hear them again, so what do you think?”
However, our signal is profoundly different from the Wow! Signal.
In fact, it lasted about three hours, instead of 72 seconds.
Also, the detection was made possible by the Parks Radio Telescope in Australia-
It was picked up around may 2019, but it wasn't noticed by the team until
October this year when one of the project's interns Shane Smith noticed it in the data.
But let's go deeper: what made this signal so intriguing? What's interesting in it?
Well, we'll start saying that there is no official paper about this signal out yet because scientists
involved are still working on the analysis. What happened is that someone leaked the story
to The Guardian newspaper, and since then, media have been chewing this up.
This is why one could think this was just a sort of trying to ride the wave, exploiting the
public's curiosity to make some audience. And that's what we were thinking, too.
But during these days we have gleaned various bits of information from the Astronomers' team,
so that we can add pieces to the puzzle, leaving the publicity topic behind.
What we know is that blc1 (yes, this is the name of the signal, and everybody knows that
astronomers are no good in giving names as well as they are not good in keeping secrets)
is a very narrowband signal at a frequency of 982.0 MHz.
In case you don't know, a Narrowband Signal is an optical signal or an electronic signal,
that has a spectral composition, i.e., a frequency spectrum, that is limited to a narrow band.
In the audio spectrum, narrowband sounds are sounds that occupy a narrow range of frequencies.
In telephony, narrowband is usually considered to cover frequencies 300–3400 Hz.
Now we don't know how narrowband it is but, to have passed the various standard tests
it is likely of order of one part in a hundred million (or better!).
The interesting thing here is that as far as we are aware, there is no astrophysical radio source
that can produce such narrowband radio signal. Do you know what does this mean?
That this signal is almost certainly artificial! Also, as a standard check in order to be sure
that the signal wasn't detected due to a flaw in the telescope, they moved it on and off-target
repeatedly. This technique is known as nodding. Now if the signal is persistent when pointing away
from the target that tells you that it's almost certainly just a flaw in your telescope and not
aliens. The breakthrough team reportedly observed this stuff for 26 hours during the campaign,
spanning multiple days and it was during one of these three-hour blocks that they
detected the 982 megahertz signal that passed this nodding test. Now, this is very interesting but
it doesn't definitively prove that the signal is astrophysical in nature after all it could
still be an orbiting satellite around the earth. But the fact that the signal persisted for three
hours is very interesting Now.
We know also that Proxima Centauri is a small, low-mass star located at 4.2465
light-years away from the Sun, and it has two confirmed exoplanets: Proxima Centauri
b and Proxima Centauri c. Proxima Centauri b orbits the star at a distance of roughly
0.05 AU (7.5 million km) with an orbital period of approximately 11.2 Earth days. Its estimated
mass is at least 1.17 times that of Earth. Proxima b is orbiting within Proxima Centauri's habitable
zone—the range where temperatures are right for liquid water to exist on its surface—but
because Proxima Centauri is a red dwarf and a flare star, its habitability is disputed.
So one could end up thinking that the blc1 signal may be
actually an artificial signal sent by the inhabitant of Proxima b. Wishful thinking!
Could this be the truth?
Unfortunately, I have to tell you that 982 megahertz frequency is indeed one
of the frequencies commonly used in telecommunications.
A radio telescope has to deal with spurious artificial signals all the time,
and that's one of the main reasons we often speak of wishing to put one on the far side of the moon,
where this wouldn't be such a problem. Since 982 MHz is a frequency used in
telecommunications, we could try to explain the signal supposing that it came from a satellite
in the so-called Leo Orbit, which whips around the Earth once every couple of hours.
In other words, they don't stay in the same position long enough to explain blc1.
So perhaps the signal is caused by a satellite in a higher orbit: one with a long slow period that
would stay stationary long enough. One possibility is the
so-called Molnija orbit satellite. The name Molnija derives from the name of the
first Soviet satellites that were positioned on orbits of this type during the sixties;
it was a constellation of three satellites capable of offering continuous coverage of
the Soviet territory, similar to that which a satellite in geostationary orbit would have had,
but centred on regions located at very high latitudes, not reachable otherwise.
These orbits aim to observe high latitude regions of the earth continuously for
surveillance or communication purposes A Molnija orbit is a highly elliptical orbit,
with an inclination of about 60°. and...Guess what?
Proxima Centauri is located at an angle some 60 degrees below the ecliptic plane.
Then these orbits are one of the rare types of satellites that would have the right inclination
to potentially pass in front of the Park's Telescope during one of these observations.
Another interesting thing about our mysterious signal is that, whenever an object that emits
an electromagnetic signal is moving relative to us, we detect a variation in its frequency.
This is due to the Doppler Effect. If the object is moving away from us,
the frequency diminishes, and if the object moves closer, its frequency increases.
This frequency variation is another interesting thing that will be analyzed in the next weeks:
it could give us information about the movement of the source (or our movement
relative to the source). But here things get complicated, and we don't know much yet.
In short, we will see how this will end in the first moths of 2021,
and we will be really happy if there will be some evidence of alien radio communication!
Anyway, just to give you an example, this is the sort of thing they’re looking for:
(IMAGE LINK:
https://sites.psu.edu/astrowright/files/2020/12/Screen-Shot-2020-12-20-at-8.49.05-AM-768x721.png)
This plot, from Howard Isaacson’s paper on the topic, shows the actual signal of extraterrestrial
technology beaming a radio signal to the Earth. In this case, it’s not aliens: it’s Voyager II.
The vertical axis is time, going up. Each bin is 10 seconds or so. The horizontal
axis is frequency, and each bin is a few Hz. Note a few things about this signal:
1. At any given moment, almost all of the power is concentrated into a single frequency bin. This is
how we know the signal must be artificial. 2. The signal’s frequency is shifting
towards lower frequencies as time increases (upwards). This is how we know the signal is
not from Earth: the telescope is on the Earth, which is rotating. As this happens the telescope
is first moving towards the source (as the source rises), then moving away (as the source sets).
Meanwhile, we just have to wait and keep dreaming! On the SETI institute website we can read:
“Yes, as long as we still don’t know, we should continue to consider the alien hypothesis viable.
After all, any SETI detection is going to be dicey when we first make it … there will be
plenty of calls for restraint intended to pacify the all-too-eager. But it’s reasonable to expect
that someday one of these suspicious signals will, indeed, be the sought-after proof of
intelligence on another world. Caution is often a good idea, but one must be careful not to toss
the baby with the bathwater. After all, this baby could change our concept of the cosmos.”
We would like to end this video recalling the famous story of Fermi Paradox.
The story goes that in 1950 Enrico Fermi and his colleagues were discussing the existence
of alien life over lunch. The question that Fermi asked the table became infamous in its simplicity:
“Where is everybody?” The room fell silent because, well, nobody had an answer.
In fact, the Milky Way is about 10 billion years old and 100,000
light-years across. If aliens had spaceships that could travel at 1 per cent of the speed of light,
the galaxy could have already been colonized 1,000 times. Why haven’t we heard from any other life?