Posts Tagged ‘SETI

The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies

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I.  Background and Justification

J. T. Wright, B. Mullan, S. Sigurðsson, M. S. Povich

We motivate the Ĝ infrared search for extraterrestrial civilizations with large energy supplies.
We discuss some philosophical difficulties of SETI, and how communication SETI circumvents them.
We review “Dysonian SETI”, the search for artifacts of alien civilizations, and find that it is highly complementary to traditional communication SETI; the two together might succeed where either one, alone, has not.
We discuss the argument of Hart (1975) that spacefaring life in the Milky Way should be either galaxy-spanning or non-existent, and examine a portion of his argument that we dub the “monocultural fallacy”.
We discuss some rebuttals to Hart that invoke sustainability and predict long Galaxy colonization timescales.
We find that the maximum Galaxy colonization timescale is actually much shorter than previous work has found (109 yr), and that many “sustainability” counter-arguments to Hart’s thesis suffer from the monocultural fallacy.
We extend Hart’s argument to alien energy supplies, and argue that detectably large energy supplies can plausibly be expected to exist because life has potential for exponential growth until checked by resource or other limitations, and intelligence implies the ability to overcome such limitations.
As such, if Hart’s thesis is correct then searches for large alien civilizations in other galaxies may be fruitful; if it is incorrect, then searches for civilizations within the Milky Way are more likely to succeed than Hart argued. We review some past Dysonian SETI efforts, and discuss the promise of new mid-infrared surveys, such as that of WISE…
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Written by physicsgg

August 7, 2014 at 7:33 pm

UK SETI Research Network

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UK astronomers to co-ordinate their search for alien signals

British scientists are to make a concerted effort to look for alien life among the stars.

Academics from 11 institutions have set up a network to co-ordinate their Search for Extra-Terrestrial Intelligence (Seti).

The English Astronomer Royal, Sir Martin Rees, will act as patron.

The group is asking funding agencies for a small – about £1m a year – sum of money to support listening time on radio telescopes and for data analysis.

It would also help pay for research that considered new ways to try to find aliens.

Currently, most Seti work is done in the US and is funded largely through private donation.

UK Seti Research Network (UKSRN) co-ordinator Alan Penny said there was important expertise in Britain keen to play its part.

“If we had one part in 200 – half a percent of the money that goes into astronomy at the moment – we could make an amazing difference. We would become comparable with the American effort,” the University of St Andrews researcher told BBC News.

“I don’t know whether [aliens] are out there, but I’m desperate to find out. It’s quite possible that we’re alone in the Universe. And think about the implications of that: if we’re alone in the Universe then the whole purpose in the Universe is in us. If we’re not alone, that’s interesting in a very different way.”

The UKSRN held its first get-together at this week’s National Astronomy Meeting.

British researchers and facilities have had occasional involvement in Seti projects down the years.

The most significant was the use in 1998-2003 of Jodrell bank, and its 76m Lovell radio telescope, in Project Phoenix. This was a search for signals from about 1,000 nearby stars. Organised – and paid for – by the Seti Institute in California, it ultimately found nothing.

Jodrell has since been updated, linking it via fibre optics into a 217km-long array with six other telescopes across England. Known as eMerlin, this system would be a far more powerful tool to scan the skies for alien transmissions.

And Jodrell’s Tim O’Brien said Seti work could be done quite easily without disturbing mainstream science on the array.

“You could do serendipitous searches. So if the telescopes were studying quasars, for example, we could piggy-back off that and analyse the data to look for a different type of signal – not the natural astrophysical signal that the quasar astronomer was interested in, but something in the noise that one might imagine could be associated with aliens. This approach would get you Seti research almost for free,” the Jodrell associate director explained.

“There are billions of planets out there. It would be remiss of us not to at least have half an ear open to any signals that might be being sent to us.”….
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Written by physicsgg

July 5, 2013 at 6:02 pm


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A Career Waiting for E.T. to Phone

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Elwood H. Smith – Copyright 2012 The New York Times Company


Jill Tarter once complained to me that she had no poetry in her soul.

It was 1990, and NASA was getting ready to undertake a survey of the 1,000 nearest stars, looking for radio signals from aliens. Dr. Tarter, then 46 and a researcher at NASA’s Ames Research Center in Mountain View, Calif., was in charge of it.

“I can’t say what they will be like,” she sighed, when asked to speculate about the nature and motives of these putative aliens.

She was far too busy worrying about how to recognize a signal, not to mention how to avoid being fooled by the kid next door or a stray weather or spy satellite.

For some three decades, Dr. Tarter, now 68, has been the person most likely to be the first to know if we make contact with E.T. — the one who will sound the alarm, spreading the news that We Are Not Alone.

Now Dr. Tarter is stepping away from the radio telescope, retiring from her post as the director of the Center for SETI Research at the SETI Institute in Mountain View. SETI, of course, refers to the search for intelligent life in the universe.

“The SETI Institute has a good pension plan — we’re grown-ups,” she said by telephone recently.

There will be a dinner and speeches in her honor at SETIcon, a gathering of astronomers, astronauts and science-fiction fans in Santa Clara this weekend.

“I hope it’s not a roast,” she said.

Dr. Tarter never did get to deliver the news that we have company. But this, she contends, is not disappointing. What would be disappointing is if humans were not able to search for their neighbors at all.

Over the decades she has brooked few distractions from that quest.

When a reporter (O.K., it was me) once described Dr. Tarter’s blond hair tied with a pink ribbon into a ponytail, she cut her hair short.

When the SETI researchers got a new radio telescope for their search — the Allen Array, at the University of California’s Hat Creek Observatory in Northern California — she got a pilot’s license so she could make the trip from her Berkeley home in one hour instead of six.

Jodie Foster’s performance as an astronomer who does make contact, in the movie “Contact,” was largely based on time she spent with Dr. Tarter.

Three times, Dr. Tarter says, she has thought we had made contact, but hard-boiled caution prevailed. Once was in France in 1980, when she and her team had to wait for a suspicious source to pass over their telescope, and Dr. Tarter was afraid to go to sleep. “I had to stay up for three days, afraid my French colleagues were going to call up Le Monde,” she said.

Another time, while she was observing with a radio telescope in West Virginia, Dr. Tarter went so far as to alert colleagues in California of an auspicious signal — and then forgot to call back when she discovered it was a satellite.

None of them was E.T. calling. Each one was another way to be fooled, another addition to Dr. Tarter’s checklist, another necessary step along a path that may or may not have an ending.

It was in the 1970s while she was pursuing a Ph.D. in astronomy at the University of California, Berkeley, and raising a daughter that she first heard of SETI: the idea that lonely species could bridge the voids between stars with radio waves. She fell in love with it after reading a NASA report on the subject edited by Barney Oliver, the former head of research at Hewlett-Packard. Reassuringly, Dr. Oliver was a crusty gear head who had made himself and others rich, not the sort of man given to romantic fantasies. Hard-boiled, you might say.

Dr. Tarter said she considered herself lucky to have been born when the issue of life in the universe had become a scientific instead of a philosophical or religious one. “For the very first time we had technology where we could do an experiment instead of asking priests and philosophers,” she said.

“It might take multiple generations,” she added, “but there were no reasons not to start with the tools I have.”

The NASA survey that Dr. Tarter led began with great fanfare on Columbus Day of 1992, the 500th anniversary of the great explorer’s arrival in the Americas — a day that she called the high point of her life, a monument to human curiosity. “I felt so proud,” she recalled.

A year later it was over, canceled at the behest of a senator, Richard Bryan of Nevada, who was skittish about “little green men.”

With help from Silicon Valley friends, Dr. Tarter and her colleagues at the institute took the search private and, over time, began to expand it farther out in space, to stars identified by the Kepler spacecraft as having planets.

Last year, however, the recession left the University of California with no money to operate Hat Creek Observatory, and the Allen Array had to be shut down, a moment that Dr. Tarter called the low point of her career.

“To have built that beautiful instrument and then have to turn it off, that hurt,” she said.

The Allen Array is now back on the cosmic search job, thanks to a deal to share observing time on it with the Air Force. But to Dr. Tarter the whole affair was a wake-up call: SETI needs a permanent endowment. “It’s on my to-do list,” she said last winter.

So she is not moving far, just down the hall, to concentrate on fund-raising. It’s time, she said, to go calling on Silicon Valley 2.0.

The search, she explained, is “too long and too difficult. If we want to attract the best and brightest, we want to be able to say, ‘It’s O.K., they can plan on raising a family.’ ”

Once upon a time it was a crazy, romantic idea, perhaps nothing better than wishful thinking. It still is, but it makes us feel bigger and more grown-up just to try. And now it comes with grown-up benefits, like a retirement plan.

There might or might not be poetry in her soul, but Dr. Tarter’s whole career has been a poem.

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Written by physicsgg

June 19, 2012 at 1:27 pm

First VLBI SETI Search Finds No Radio Transmissions

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… From Gliese 581

Astronomers have completed the first search for extraterrestrial intelligence on nearby exoplanets using very long baseline interferometry

uv coverage of the LBA observation of the Gl581 system, in units of mega wavelengths. The x-axis plots the u coordinates, while the v coordinates is on the y-axis

A telescope’s angular resolution is its ability to distinguish small details of a distant object. The Hubble Space telescope, for example, has an angular resolution of about 100 milliarcseconds. 

That’s good but by no means the best. In fact, the telescopes with the highest angular resolutions are interferometric radio telescopes, made up of several dishes spread over thousands of kilometres.

Known as very long baseline interferometers (VLBIs), the biggest boast an angular resolution some two orders of magnitude better than Hubble.

So what to point them at? Today, Hayden Rampadarath and pals at the International Centre for Radio Astronomy Research at Curtin University in Australia say they’ve pointed their interferometric radio telescope at Gliese 581, a red dwarf star some 20 light years from here. 

What makes Gliese 581 interesting is its planets, which include two superEarths that probably sit on the edge of their habitable zone. 

That makes them good candidates for life. And if this life is anything like our own, it may already be broadcasting at radio frequencies that we can tune in to.

Although VLBI has extraordinary angular resolution, it has never been used to look for signs of extraterrestrial intelligence. So this is an important proof-of-principle step. 

The Australian instrument, known as the Australian Long Baseline Array, consists of three radio telescopes a few hundred kilometres apart, which gives them an angular resolution that is about the same as Hubble’s.

Rampadarath and pals pointed it at Gliese 581 for a total of 8 hours in June 2007, tuning into frequencies close to 1500 megahertz.  Why they’ve waited so long to publish their result, they don’t say but their paper has now been accepted for publication in The Astronomical Journal.

What they found is interesting. VLBI techniques turn out to be useful for SETI searches because they automatically exclude many terrestrial sources of interference that might otherwise look like SETI signals. That’s because the same signals have to show up at all the telescopes several hundred kilometres apart.

In total, Rampadarath and co found 222 candidate SETI signals. However, they were able to exclude all of these relatively easily using automated analysis techniques, which have become increasingly sophisticated in recent years. (That’s partly because of projects such as SETI@Home which has found billions of interesting signals, all of which have turned out to be false alarms.)  

The false alarms picked up by the Australian Long Baseline Array probably came form Earth orbiting satellites, say the team.

Of course, this doesn’t exclude the possibility of intelligent life in the Giese 581 system or even exclude the possibility that these ETs might use radio signals to communicate. 

Instead, it  places limits on the strength of these signals and not particularly onerous ones at that. Rampadarath and pals say  their instrument would have picked up a broadcast with a power output of at least 7 megaWatts per hertz. 

To put that in context, on the slim chance that Gliese inhabitants had been broadcasting directly to Earth using an Arecibo-style dish, Rampadarath and co would have easily picked up the signal. (Arecibo is a 300 metre radio telescope in Puerto Rico).

On the other hand, the ordinary radio transmissions like those  we continually broadcast into space, would have been far too weak to be picked up by the Australian team.

That’s not to say that this kind of observation won’t be possible in future. The Australian array is by no means the biggest of most sensitive instrument available today. 

What’s more, astronomers are planning a new VLBI telescope called the Square Kilometre Array which will have the sensitivity to pick up broadcasts of a few kiloWatts per Hertz from 20 light years away.

There are no shortage of targets. At the last count, astronomers had found around exoplanets that sit in their habitable zones (meaning they’re warm enough for liquid water). These places are of intense interest.

Time on VLBI telescopes is precious and difficult to come by. But the prize here is of almost incalculable value–the discovery of intelligent life beyond the Solar System. 

So it wouldn’t be a complete surprise if radio astronomers found ways to hunt more often for radio broadcasts from new and exciting exoplanets.

Ref: :The First Very Long Baseline Interferometric SETI Experiment

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Read also: ‘No signal’ from targeted ET hunt

Written by physicsgg

May 31, 2012 at 2:35 pm

How would the public react if Seti found evidence of alien life?

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‘In a sense, we’ve run that experiment,’ says Seth Shostak, chief alien hunter at the Search for Extraterrestrial Intelligence

Seti uses the Allen Telescope Array to monitor thousands of stars for radio signals that have the imprint of alien intelligence. Photograph: Ben Margot/AP

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May 21, 2012 at 1:26 pm

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Time to give SETI a chance

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by Jill Tarter – newscientist

Earth 2.0 is in our sights. Checking it for signs of life will be the next big issue

THE thousands of probable worlds discovered in orbit around other stars are making our corner of the universe appear a lot friendlier to life these days.

The Kepler space telescope, which has its eye on 150,000 stars, is beginning to home in on Earth-size planets. Can Earth 2.0 be far behind? What will it be like?

Earth 2.0 would be a rocky planet the size of our own, orbiting a star like the sun at a distance where the surface temperatures would allow liquid water oceans, assuming the planet was sheathed in an atmosphere containing greenhouse gases.

In other words, it will be a world that we might find habitable. We won’t be able to see this other Earth directly, but we will know it is there because of the influence it has on its star. Even so, we will inevitably ask: “Is it inhabited?”

Answering that question will be hard. It is quite probable that Earth 2.0 will be hundreds or even thousands of light years away; too far from us to detect trace chemical “biosignatures” that would suggest life.

There is another way. We could look for life on Earth 2.0 via “technosignatures” such as radio signals produced by intelligent life. These would be cheaper and easier to find than biosignatures. It is a long shot, but one that is affordable and we can do it now. In fact the Search for Extraterrestrial Intelligence (SETI) has been on the case since the 1990s.

Despite being denied public funds and derided by some politicians for seeking “little green men”, SETI still carries out searches with private money.

For decades we have blindly checked the sky overhead or targeted stars that are old enough, metallic enough and stable enough to have rocky planets in the right orbits. Now, thanks to Kepler, we know where to look. Digital technologies are speeding up the searches, but they require investment to reap the rewards.

SETI is a logical addition to the publicly funded endeavours exploring other worlds. It is time to fund it properly, either with public money or privately.

Now that we know there are planets beyond our solar system, and where to find them, we should give SETI a fighting chance to see if anybody is home.

Jill Tarter is director of the Center for SETI Research at the SETI Institute in Mountain View, California

Written by physicsgg

February 12, 2012 at 11:58 am

The Fermi Paradox, Self-Replicating Probes …

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… and the Interstellar Transportation Bandwidth

Keith B. Wiley
It has been widely acknowledged that self-replicating space-probes (SRPs) could explore the galaxy very quickly relative to the age of the galaxy. An obvious implication is that SRPs produced by extraterrestrial civilizations should have arrived in our solar system millions of years ago, and furthermore, that new probes from an ever-arising supply of civilizations ought to be arriving on a constant basis. The lack of observations of such probes underlies a frequently cited variation of the Fermi Paradox. We believe that a predilection for ETI-optimistic theories has deterred consideration of incompatible theories. Notably, SRPs have virtually disappeared from the literature. In this paper, we consider the most common arguments against SRPs and find those arguments lacking. By extension, we find recent models of galactic exploration which explicitly exclude SRPs to be unfairly handicapped and unlikely to represent natural scenarios.
We also consider several other models that seek to explain the Fermi Paradox, most notably percolation theory and two societal-collapse theories. In the former case, we find that it imposes unnatural assumptions which likely render it unrealistic. In the latter case, we present a new theory of interstellar transportation bandwidth which calls into question the validity of societal-collapse theories.
Finally, we offer our thoughts on how to design future SETI programs which take the conclusions of this paper into account to maximize the chance of detection….
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November 29, 2011 at 7:18 am


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Detection Technique for Artificially-Illuminated Objects ….

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….in the Outer Solar System and Beyond

Abraham Loeb and Edwin L. Turner
Existing optical telescopes and surveys can detect artificially-illuminated objects comparable in total brightness to a major terrestrial city at the outskirts of the Solar System.
Orbital parameters of Kuiper belt objects (KBOs) are routinely measured to exquisite precisions of <10<sup>-3</sup>.

Here we propose to measure the variation of the observed flux, F, from such objects as a function of their changing orbital distances, D.

Sunlight-illuminated objects will show a logarithmic slope α=(dlogF/dlogD)=-4 whereas artificially-illuminated objects should exhibit α=-2.

If objects with α=-2 are found, follow-up observations with large telescopes can measure their spectra to determine if they are illuminated by artificial lighting.
This method opens a new window in the search for extraterrestrial civilizations.

The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars……..
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November 1, 2011 at 3:05 pm


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