New Radio Facility Could Detect Earth-like Civilizations Around 1,000 Nearest Stars

Science Daily ^ | January 8, 2007 | Harvard-Smithsonian Center For Astrophysics

[Brilliant]

Astronomers have proposed an improved method of searching for intelligent extraterrestrial life using instruments like one now under construction in Australia. The Low Frequency Demonstrator (LFD) of the Mileura Wide-Field Array (MWA), a facility for radio astronomy, theoretically could detect Earth-like civilizations around any of the 1,000 nearest stars.

"Soon, we may be eavesdropping on signals from Galactic civilizations," says theorist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA). "This is the first time in history that humans will be capable of finding a civilization like ours among the stars."

Loeb will present his findings on Wednesday, January 10, in a press conference at the American Astronomical Society meeting in Seattle, Wash.

Previous SETI programs would not have detected an Earth-like civilization. The searches often looked for beacon-like signals deliberately beamed across space. Such beacons may not exist. Also, most radio SETI projects examined frequencies higher than 1 Gigahertz in order to avoid interference from both Earth-based and natural cosmic sources.

Instead of looking for deliberate broadcasts, Loeb and his co-author Matias Zaldarriaga (CfA) suggest looking for accidental leakage from an alien civilization. They point out that the new MWA-LFD, which is designed to study frequencies of 80-300 Megahertz, will pick up the same frequencies used by Earth technologies. On Earth, military radars are the most powerful broadcast sources, followed by television and FM radio. If similar broadcast sources exist on other planets, facilities like MWA-LFD might detect them.

"The MWA-LFD is a science instrument intended to study the distant, young universe," explained Zaldarriaga. "But by piggybacking onto its normal observations, SETI researchers could use it to look for E.T. civilizations."

A SETI program at the MWA-LFD would complement other SETI projects. It will observe a larger area of the sky over a longer period of time and in a different frequency range.

Loeb and Zaldarriaga calculate that by staring at the sky for a month, the MWA-LFD could detect Earth-like radio signals from a distance of up to 30 light-years, which would encompass approximately 1,000 stars. More powerful broadcasts could be detected to even greater distances. Future observatories like the Square Kilometer Array could detect Earth-like broadcasts from 10 times farther away, which would encompass 100 million stars.

If alien broadcasts were detected, additional observations could measure characteristics of the source planet, such as how fast it rotates or how long its year is. By combining that information with knowledge of the parent star, astronomers could estimate the temperature on the planet's surface to assess whether it may have liquid water and life as we know it.

The MWA-LFD is a radio telescope designed to detect and characterize highly redshifted 21-centimeter emission from hydrogen molecules in the early universe. Its key scientific goal is to create a three-dimensional map of ionized "bubbles" that formed as the first quasars and galaxies flooded space with ultraviolet light billions of years ago.

The paper describing these findings has been accepted for publication in the Journal of Cosmology and Astroparticle Physics and is available online at http://arxiv.org/abs/astro-ph/0610377.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Note: This story has been adapted from a news release issued by Harvard-Smithsonian Center For Astrophysics.

[cripplecreek]

The chances of finding anything among the 1000 nearest stars is pretty low but I wish them luck just because it's cool stuff.

[Brilliant]

You're right about that. 100 million stars, and your chances are a little better.

[Professional Engineer]

A SETI program at the MWA-LFD would complement other SETI projects. It will observe a larger area of the sky over a longer period of time and in a different frequency range.

Cool.

[billorites]

The RIAA will be right there to bust the aliens for file sharing.

[Lurker]

May be of interest.

L

[Brilliant]

Yes, but the Dems will grant them amnesty.

[Vn_survivor_67-68]

Spectrum is infinite, limited only by the (frequency) technology to access it, yes?

I think that earthbound mankind has (even at this "late" date in the RF era) only made the beginning steps to use frequency. I believe that whenever we make some exponential advances in frequency technology we will easily find extraterrestrial civilizations; and that until such time we will make contact only if alien beings wish to make contact with us.

[Little Pig]

bookmark

[CrawDaddyCA]

Maybe this technology can be used to prove, once and for all, the presence of Klingons around Uranus!

[onedoug]

Search away. They won't find anything.

[dr_lew]

I can't say this is impossible, but I can wonder how it is possible, based on a very simple consideration.

Suppose there is a 100 Megahertz signal radiating 1 Megawatt per steradian ( e.g. 4pi Megawatts radiated over the whole unit sphere. ) The energy per photon is Planck's constant times 100 Megahertz, and the number of photons per second per steradian is 1 Megawatt divided by the energy per photon, or about 1.5e31 photons per second.

The area subtending a steradian at a distance R is just R^2, and the photons per second crossing a square meter at distance R is 1.5e31/R^2. At one lightyear ( ~ 1e16 meters ) this is about 0.15 photons/second, so we require an antenna about 2 meters across to receive 1 photon per second, and at a distance of 30 ly, this becomes 60 meters across.

Well, maybe this is just the way they're figuring it, about one event per second, to be discerned ... how? ... from a background of ... what? ... millions? trillions? ... of times greater.

I suppose I'll have to read their paper!

BTW, I went through this years ago when SCIENCE magazine carried an article about the RF signature of earth from distant space. They said the strongest earth signal was some kind of US Navy beacon.

[JerseyJohn61]

bump

[Calvin Locke]

They said the strongest earth signal was some kind of US Navy beacon.

I doubt that's true. Think about it. It would be radiating roughly half a sphere, depending on its purpose.

My guess would be military radar pointed skyward. I saw a show that showed a British equivalent of NORAD facility, 2MW radiating from a triangular pyramid.

[Reaganwuzthebest]

Search away. They won't find anything.

That's a strong possibility. Space is so huge that even if other intelligent life does exist it would be like finding a needle in an endless haystack.

[Clinging Bitterly]

I don't know. Contemporary advances in RF technology have trended toward increasing the use of digital modulation and signal processing techniques to make more efficient use of the same spectrum that's been widely used for the last 40 years or so. The physical environment of the earth itself places practical limits on the use of super high frequencies.

But this article is thought provoking. First, advanced digital signal processing (DSP) makes it easier to query the broad spectrum of noise falling on those square kilometer arrays for patterns that would be, by definition, intelligence.

But what would those pattern look like? RF could, and most likely would, behave quite differently on worlds who's size, mineral content, magnetic fields, atmosphere and so forth differ from our own, so what a distant civilization might be actually doing with radio could be quite different than what we are doing here.

Finally, how advanced are these distant civilizations likely to be? An important question considering: Human civilization has used RF as a means of conveying information for just about a hundred years now, and I am quite certain in another hundred years our means of communicating over distance will be quite different than it is today. We may well have a band of satellites in the Clarke belt (or just as likely arrays of them in low earth orbit, or even a more advanced cellular type terrestrial network) that transmit and receive individually addressed and highly directional digital signals over key pairs, perhaps indistinguishable from the noise floor without the keys. I actually expect our primary technology to resemble something like this in much less than a hundred years. We don't have the computing power on earth to even crack PGP. So here we have at our stage of evolution, a tiny speck of time where we, ourselves, emit RF signals that are detectable with the technology we posses, so if something is out there, it's going to be awfully hard to find.

But we have to explore that, don't we?

[SunkenCiv]

Thanks, Lurker! So much easier to find Earthlike planets using the alien equivalent of "Leave It To Beaver". :')

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[dr_lew]

I find my own synopsis from 1982:

This is a synopsis of "Eavesdropping: The Radio Signature of the Earth",
by W.T. Sullivan, S. Brown, and C. Wetherill in the 27 Jan 1978
issue of "Science".

The authors report on an extensive and thorough analysis of the
probable radio appearance of the earth from ~1 light year. The
principal conclusions:

1) The most distantly detectable radio emission is from BMEWS (Ballistic
Missile Early Warning System) radar. An Arecibo-like antenna could detect
it at ~18 light years.

2) The richest source of distantly detectable radio emission is UHF and
VHF TV broadcasting detectable at ~1.8 light years by Arecibo (carriers only,
program demodulation would require ~2e4 times the sensitivity.) The
authors analyze the appearance of about 2000 major stations due to scheduling,
geography, and diurnal and orbital motion of the earth. Broadcasts at
frequencies less than 20Mhz are contained by the ionosphere.

[Bender2]

Gad! Tell those guys at SETI when they finally find a signal and...

If'n them Aliens are a coming... Please, please! Please give me a day's notice...

So I can have the time to get my false tooth set properly, do a load of laundry for clean drawers to wear, get my glass eye polished, the gears and struts adjusted in my wooden legs, new batteries for my hearing aids, a haircut, change to a new colostomy bag, trim my nose and ear hair... And take enough Bean-O to keep the local air fresh... And quite, too!

I don't know about the 'old farts' out Alien's way, but here abouts, we Earth bound 'old farts' need our lead time to keep our honor and dignity intact!

[hosepipe]

[ New Radio Facility Could Detect Earth-like Civilizations Around 1,000 Nearest Stars ]

UNless as Occams law suggests they are NONE ANYWHERE..