Did we receive an extraterrestrial signal in 1977?

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Did we receive an extraterrestrial signal in 1977?
4 months ago


In 1977 a scientist listening to a SETI radiotelescope trying to find out alien civilizations noticed a strong signal at 1420.35 MHz coming from near the direction of the Tau Sagittarii star (Tau Sgr for short). The signal was thirty times more powerful than any other radio emission at that time. It lasted for the maximum duration our radiotelescope could record it, for 72 seconds (maybe it lasted more but we can't know).

He tried to find the signal again but it wasn't repeated. Others also tried unsuccessfully to find a repetition of the signal. Never again we heard something similar from the direction of the Tau Sgr star.

The frequency of the signal isn't random, it is near the hydrogen line which is a special frequency for the whole universe. Scientists believe that this frequency would be a good choice for an alien civilization wishing to send interstellar signals. But for 50 years the SETI research has failed to find other signals in the hydrogen line.

The 1977 signal, now known as the "wow signal", is currently the only radio signal we have received which could have been produced by an extraterrestrial civilization. Two other signals thought of being of alien origin have since been identified as natural phenomena, but the 1977 signal is still unexplained. Nothing rules out the possibility of being a "hello" message by an extraterrestrial civilization.

The Tau Sgr star is 122 light years away, which means the signal wasn't emitted at the same time we received it. If the alien civilization that beamed this signal is on a planet in orbit the Tau Sgr star, then they probably emitted the signal in 1855. http://en.wikipedia.org/wiki/1855

Since light needs 122 years to travel between Earth and Tau Sgr, if the aliens noticed something strange in our atmosphere that made them beam what might have been a "hello" signal then we can conclude that when they beamed it our Earth was visible to them as it was in 1733. http://en.wikipedia.org/wiki/1733 So if the signal was the response to something we humans did then it was something we did in either the late 17th century or the early 18th century. http://en.wikipedia.org/wiki/17th_century or http://en.wikipedia.org/wiki/18th_century

Attempts to find again the same signal continued at least until 1999, so we know the aliens didn't beamed another signal until at least 1877. If they had sent another signal in 1892 then we should hear it now in 2014.

In 2012, scientists sent a reply towards the direction of the Tau Sgr star. Because the Tau Sgr star is 122 light years away, the alien civilization that may exist near there will receive the signal in 2134, if they are tuned to the correct frequency at the right time to hear it.

We started polluting the space with radio programs since a hundred years ago and with television programs since fifty years ago, therefore the extraterrestrial civilization at Tau Sgr will hear our earlier radio broadcasts around 2030-2040 and our first television broadcasts around 2080-2090. If they send a reply to our radio broadcasts we will receive it in 2152, whereas a reply to our television broadcasts could be received by 2202.

The only thing we know about the 1977 signal is that it was very powerful. This means that the alien civilization that generated this signal should be an extremely advanced technological civilization because such a signal would require a 2.2 GW transmitter, whereas our most powerful transmitters are only 2.5 MW!

So, if the signal was alien, we have a very powerful civilization in our neighborhood. If we assume their spaceships can travel at 10% of the speed of light and they launched a probe now, then they could land on Earth in the year 3234, whereas if they launched their probe in 1855 then it would land on Earth in 3075. If they can travel at the speed of light and they launch their spacecraft now then it could reach us in 2136, whereas if they launched their probe together with their emitted signal in 1855 then the alien spacecraft if it travels at the speed of light should have already been here. Since we haven't seen any spacecraft approaching, it's safe to assume that their spacecraft can't travel at the speed of light. But if they travel at 50% the speed of light and they launched their probe in 1855 then they could land on our planet in 2099.

Our fastest spacecraft is the New Horizons which has a speed of 59,000 km/h whereas the speed of light is 1.08 million km/h. This means if we launched a spacecraft towards the aliens this year, we would land on their planet after two millennia in the year 4246 assuming our spacecraft had a constant speed of 59,000 km/h if my calculations are correct and I didn't screwed it up.

What do you think? Did we receive an alien signal in 1977? It had all the expected characteristics of an extraterrestrial civilization's contact attempts, it was powerful (much more powerful than our own transmitters) and it was emitted at the special frequency of 1.4 GHz. The only problem is that we never heard the same signal or anything similar again. It was an one-off event. Why did the aliens chose not to repeat the signal?

We know that the Tau Sgr star has 2 times the mass of our Sun and 16 times our Sun's radius. It is a big star, but scientists suspect it is actually two stars that travel together as a pair. However, we don't know for sure whether it's one or two stars. Scientists also think that Tau Sgr has probably an orange color and has less metallic content (iron and other metals) than our Sun. This could suggest that the alien civilization may face a shortage of industrial metals like iron, whereas our solar system probably has more iron than theirs. Could we expect them to want to trade their scientific knowledge for our iron? Scientists also believe Tau Sgr traveled there from another part of the galaxy, but I don't know what this might mean about the aliens.

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