WOW! Interstellar Spam?

June 24, 2008

It was an eerie experience for me on my first visit to a radio telescope that was  searching for signals from extraterrestrial civilizations.

Several years ago I stood under the 26-meter dish antenna at the Oak Ridge Observatory in Harvard, Massachusetts. It was being used that night to look for signals from E.T. under a program called project META (Megachannel Extra-Terrestrial Assay).

What made me feel lonely, in a spooky way,  was the silence. Myriad stars hung above the probing ear of the telescope.  In a nearby electronics shack a bank of parallel PC computers chugged away furiously at analyzing the radio spectrum.

To me the stars seemed stubbornly, capriciously silent. 

There were so many stars, and so many potential homes for intelligent life. Yet, there wasn’t a whisper on this night or any other night that the SETI (Search for Extraterrestrial Intelligence) experiment was underway.

This personal experience is in stark contrast to a strong, brief burst of radio energy received on August 15, 1977 at the Big Ear radio telescope at the Ohio State University.

The signal was narrowband, meaning that all of its energy was concentrated into a small part of the electromagnetic spectrum.  It had the trademark of what would be expected from an artificially produced interstellar broadcast.

But the burst lasted for merely 72 seconds. And, it has never reappeared again despite numerous SETI follow-up observations. This event remains as ephemeral as a ghost sighting. 

When astronomer Dr. Jerry Ehman circled the signal data on the computer printout, he wrote the comment "Wow!" on the side. This notation became the name of the signal, which has since become legendary.

But I never gave this SETI hiccup much thought until I realized that the beam came from the direction of the summer constellation Sagittarius. Of the 88 constellations on the sky Sagittarius is the Monopoly game’s “Boardwalk” and "Park Place” on the sky.

Why so special?  Because it lies in the direction of the galactic center. This is a region of the Milky Way galaxy that contains the highest density of stars because we’re looking right into the hub of our star-city. It includes some of the oldest stars in our galaxy.

Sagittarius is the first constellation I would pick to go looking for signals from E.T.

This alone convinces me that the WOW signal was probably a real transmission from an extraterrestrial civilization. What are the chances that out of all the constellations on the sky a weirdo manmade radio artifact just happens to pop up in the direction of Sagittarius?

Photos, top to bottom: Harvard University; SETI; DSS

At a recent astrobiology meeting I sheepishly approached veteran SETI astronomer Frank Drake about the WOW signal. I half expected him to say: “Oh that silly thing!”

Instead, Drake shared the same belief that it was a real interstellar message. (Dr. Ehman has cautiously addressed the same conclusion as a "definite maybe" after ruling out all Earth radio interference explanations.)

Drake speculates that the signal may have been crammed with a packet of information at too high a rate for the Big Ear telescope to resolve.

But why so brief? Drake suggests that an alien civilization may be pinging stars with information packets, a sort of galactic spam. Once the packet is decoded it yields information for tuning to another channel to receive a longer and more detailed message.

So, toward the end of the 20th century humankind may have received the first fleeting evidence of intelligent life off the Earth.

But anything totally strange can happen just once.

Will a WOW signal ever happen again?

Comments

[birdwatch]

So tell us, Cosmic Ray: Do you know if the Allen Telescope Array being put together by SETI Institute and partners will be honing in on sector Wow? Great post, btw
Irene

[Ray]

Irene,

yes! I understand that the WOW coordinates are on the Allen Array's list of "to-Dos"

Ray

[Dave Mosher]

That "WOW" among the more technical names on the star map image is really funny - makes me think we should start naming celestial objects after fun phrase: "Gee whiz!" "Golly gosh!" "Holy smokes!" "Shazam!"

[Mark Wright PhD]

Dan Wertheimer, chief scientist for the SETI@home project, says the Wow signal was almost certainly pollution: radio-frequency interference from Earth-based transmissions. To quote Dan: "We've seen many signals like this, and these sorts of signals have always turned out to be interference,".

BTW the fact that the galactic centre contains the greatest density of stars is not necessarily a good thing when it comes to searching for extra-terrestrial life, on the contrary in fact. Greater star density = greater likelihood of a planetary cataclysm occurring, such as supernovae occurring within (relatively) close proximity of a planetary system, or a nearby magnetar, both with obvious repercussions on biospheric integrity.

As a starter for anybody interested in this subject and the possibility of 'ET' life in general I would refer to http://en.wikipedia.org/wiki/Rare_Earth_hypothesis for a overview in respect of why targeting the galactic centre is not necessarily such a good idea, and why ET life, especially complex multi-cellular life, may be not as common as some people obviously anticipate. Another overview unconnected with the Rare Earth hypothesis but covering the main points of planetary habitability is given at http://en.wikipedia.org/wiki/Planetary_habitability.

[ray]

Mark

Let me clarify that the galactic center direction is optimal because a large number of stars stretch along the line-of-site. So it's not just those stars in the rough and tumble region of the galactic core.

Exoplanet searches using microlensing and transits are done in this preferred direction because of the high stellar density.

It's my understanding that the Wow! signal is markedly different from other anomalous SETI false detections.

for reference:

http://www.bigear.org/Wow30th/wow30th.htm

[Dave Mosher]

Cool point Ray, about line-of-sight. Really highlights the fact that we can only search for life in a tiny portion of the galaxy at a time.

[Mark Wright]

I am aware that there will be more stars along the line of site in the direction of the galactic center, and didn't mean to imply just the galactic core when I referred to that. Nonetheless, as is explained in the Wiki links above, the number of possible habitable worlds will decrease the closer in you get to the galactic core - just because there is a higher apparent stellar density along the line of site in this direction doesn't mean that it is a better bet for finding life, all it means is that a greater number of probably lifeless stellar systems can be scanned per unit time, as only a fraction of these line of site stars will reside in the likely galactic 'habitable zone'.

It is a great shame that the TPF has been deferred and is currently without funding, as this must be a good bet for at least identifying target habitable worlds.

[Joepi]

"Will a WOW signal ever happen again?"

Probably not... My English is a little rusty, so bare with me.

If your looking for, intelligent live, I’m guessing they won’t use 'our normal radio wave', it’s clearly a big problem sending and receiving messages, with this form of wave.

You just need to much power to send a simple message across galaxies, and if I remember correct the speed of the type of wave used by seti will not exceed 1200km.

So infect, we are hoping to find intelligent live, with a live span much greater than ours, with a technique, that is probably not even in use, anymore by a 'level 1 civilization on the kardashev scale'.

And if, the intelligent live, is populating other planets/galaxies, they surly need a better way of communications, then are available to us today.

[Lori Cuthbert]

Is it possible that WOW was a regular stutter of some kind by a celestial body, instead of a fabricated signal?

[ray villard]

Lori

A transient phenomenon a little reminiscent of the WOW signal is the gamma-ray bursts (GRBs) that mystified astronomers for decades. In the early days the joke was that they were alien starship exhaust. They are typically a few seconds in duration but can range from a few milliseconds to several minutes.

The big difference it that one pops up somewhere in the universe once a day! And, they are too far away to be artificially produced because the power requirements and vastly beyond anything an alien could light off. Today we know the come from the biggest stellar explosions in the universe - hypernovae.

In the 1960s, the so-called pulsars (pulsating stars) were dubbed LGMs for Little Green Men. The radio pulses came with such precision timing it looked artificial. But again, the energy was enormous, and astronomers found a much simpler explanation -- rapidly spinning neutron stars that whirl like your kitchen blender on puree.

So, the WOW signal conceivably could be some extraordinarily rare and weird natural phenomenon. But in this case an alien transmission might be the simpler explanation. There's no theoretical astronomical model or prediction. And, only one not-repeating event leaves you pretty clueless.

[Anne]

I wonder how big the area is where the signal came from. I mean how many stars fit in there? Have these stars already been investigated for (earthlike) planets?

[Ray Villard]

Hi Anne

I've added a sky survey photo to the blog that centers on the approximate coordinates. There is a two arcminute discrepancy between the two antenna feeder horns that picked up the signal, so no specific star can be pinpointed. The field is very rich in stars because it is near the galactic plane. So this is like looking for the proverbial needle-in-haystack.

[Trevor]

This is a really great post. I was not previously aware of the significance of the location of the signal in Sagittarius. As the best known SETI event WOW has been scrutinised for more than 30 years and I agree that a signal of extra terrestrial origin is the most likely explanation. It may be that the detection of this signal was a billion to one shot - the cosmic equivalent of a lottery win. If the signal was genuine maybe we need to have a dish permanently focused on this area of the sky. If signal appears again we need to give us the best chance of picking it up.