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lunes, 21 de junio de 2010

Are We Overlooking Alien Beacons?

Last week Hubble Space Telescope images definitively showed that the bright flash of light seen on Jupiter was simply a meteor. Albeit, a blinding bright meteor to be seen across 400 million miles of interplanetary space. As reported by Ian O’Neill Hubble failed to find any telltale debris as seen in Jupiter comet and asteroid impacts.

Now Hubble astronomers tell us that Jupiter super-meteors might be detectable as frequently every few days. Australian amateur astronomer Anthony Wesley just got lucky because he was viewing a video transmission of Jupiter when the brilliant flash appeared.

This event was sobering to me because my mind invariably wandered to wondering if a signal from an extraterrestrial civilization might be just as transient.

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Despite our best search strategies, are signals from E.T. manifested in anomalous flashes of radio energy from our galaxy that are missed, or dismissed as natural phenomena? Maybe alien transmissions are popping off all around us but we just aren’t looking at the right place or right time to seen them.

In a recently published paper by James Benford and Dominic Benford of Microwave Sciences in Lafayette, California, the authors imagine that SETI beacons might be much like a lighthouse, sweeping the galactic plane in a raster pattern. Depending on beam size and scan rate, many days could pass between the brief Twitter-like bursts of “here we are” flashes from alien civilizations.

"We should learn how to identify any such beacons," the authors say. For starters they expect the beam would pulsate to conserve energy and also have amplitude or frequency modulation of the carrier to draw attention to itself.

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The problem is that pulsars (powerful bursts of radiation from rotating neutron star magnetospheres) look just what an alien transmission might look like according to this SETI "lighthouse" model. In fact when pulsars were first discovered in the mid 1960’s they were nicknamed “LGMs” for “Little Green Men.”

There are certain unusual transient phenomena that are likely due to pulsars behaving, well, unusually. These occasionally repeat, but others do not. The authors say that we should consider SETI beacons as a candidate explanation when perplexing non-repeating signals that are seen in the radio sky.

One example they cite is PSR J1928+15 that was a transient burst of radio pulses that was observed only for two minutes in 2005 near the galactic plane -- and never repeated in several dozen subsequent searches. Three pulses came in succession. The first and third pulse was down a factor of ten from the powerful central pulse. The source is estimated to be 26,000 light years away, the distance to the heart of our galaxy.

The SETI-lighthouse hypothesis would explain PSR J1928+15 as an E.T. scanning beacon. As it swept past Earth, the giant Arecibo radio telescope in Puerto Rico caught the central pulse of the true beam. The first and third pulses were at the edges of the beam width according to this interpretation.

Pulsar seti
A far simpler explanation is that the transient was caused by an asteroid falling into the neutron star from a circumpulsar disk. This perturbed the pulsar’s intense magnetic field.

If we diligently apply Occam’s Razor (going with the simplest explanation) the crashing asteroid solution wins over E.T. saying “Hi.”

Also, the central beam pulse was 190,000 terawatts -- 10,000 times the total power output of our civilization! I wouldn't want to pay that electric bill.

Still, this kind of mega-engineering would be cheaper than the ticket price high-speed interstellar travel. The authors say there might be a scaling effect where super-civilizations build extraordinarily powerful transmitters. These aliens might have limitless armies of self-replicating machines that tirelessly construct vast antenna arrays orbiting a star and sucking up solar energy.

Another problem is that such civilizations are probably rare in the galaxy. And, at the same time we need to assume that they’d decide to stick with radio wavelengths as a viable communications channel for reaching any entities they would be interested in contacting.

Less ambitious or less advanced civilizations might try beacons too, but the beams would be weaker, though likely to be more numerous in the galaxy.

Seti array

The dilemma is that exotic astrophysics theories, no matter how exotic, would always trump any conclusion that super-aliens where pumping out extravagantly powerful broadcasts. Even suggesting “I fount E.T.” could be a career-killer for any young astronomer.

If such artificially produced flashes are real, they will likely remain ghosts in the cosmic night that are as fleeting as Jupiter’s super-meteors.

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