An artist’s impression of Gliese 581d, an exoplanet about 20.3 light-years away from Earth, in the constellation Libra. Credit: NASA

First SETI Search of Gliese 581 Finds No Signs of ET

5 Jun , 2012 by

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The first targeted SETI search of a system with a potentially habitable world has come up empty, but perhaps finding signals wasn’t the main objective in this search. Back in 2007 a group of astronomers used the Australian Long Baseline Array to listen for radio signals from Gliese 581, a red dwarf star that is now known to host at least six planets, with one in the star’s habitable zone. This was a SETI-type search for extraterrestrial-made signals, and it initially found 222 candidate signals. However, the team was able to reject all of them using automated analysis techniques, determining they were caused by Earth orbiting satellites. So why is this potentially good news?

This search was actually a proof of concept for using the Very Long Baseline Interferometry (VLBI) for targeted SETI searches, and that it worked well is great news for future searches that look specifically at a particular star system. Until recently most SETI searches were wide sky surveys, scanning wide, random areas of space looking for radio signals. But now, with the success of the exoplanet hunting Kepler mission, we now know of some potentially habitable systems and planets, and astronomers can do targeted searches, looking at specific spots in the sky.

It wasn’t known if the VLBI technique would be successful for such a “directed” targeted search, but this search by Hayden Rampadarath and team from the International Centre for Radio Astronomy Research at Curtin University in Australia proves it does.

The Australian Long Baseline Array is a combination of three radio antennae: the 22-meter Mopra Telescope, Parkes Observatory and the Australia Telescope Compact Array (ATCA) which are each a few hundred kilometers apart from each other. The data from the three locations are combined, making them act as one huge radio telescope, with an extraordinary angular resolution in the milli-arcsecond regime, the highest resolution in astronomy. And it turns out that VLBI techniques are great for SETI searches because they automatically exclude many Earth-based 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 kilometers apart.

The team pointed the telescopes at Gliese 581 (Gl581), located 20 light-years distant in the constellation Libra for about 8 hours, tuning into frequencies close to 1500 megahertz.

The team said that the array would have been able to pick up a broadcast with a power output of at least 7 megaWatts per hertz, which means that if Gliese inhabitants had been broadcasting directly to Earth using an 300-meter Arecibo-style dish, the signals would have easily been picked up. However, ordinary radio transmissions, such as the ones Earthlings regularly transmit into space, would have been too weak to be detected.

But this bodes well for using other more powerful VLBI arrays such as the European VLBI Network, current most-sensitive VLBI array in the world or the upcoming Square Kilometre Array, which will have the sensitivity to pick up broadcasts of a few kilowatts per Hertz from 20 light years away.

So while this doesn’t mean that there is no life in the Gliese 581 system, this does mean we now have an expanded arsenal of tools for looking.

Read the team’s paper.

Source: Technology Review Blog

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henk
Member
henk
June 5, 2012 5:47 PM

We do not even know if there is a planet with life there, So it is not a surprise. We will never find a other intelligent life form because we are the only one in this galaxie.

Seti is a wast of time

Maybe 1 in the 10000 spiral galaxies have 1 intelligent life. We will never meet them and they will never meet us. We just need to except that we are alone in our part of the universe.

There is good news we will never fight a war with a other intelligent species and this galaxie will belong to the human race

Bill
Member
Bill
June 5, 2012 6:39 PM

you don’t think that statement is a bit too… definitive?

Severin
Guest
June 5, 2012 8:19 PM
First of all, we will neven know if we don’t look. The fact is that we can’t rule out other civilizations out there, just like we can’t rule out that we are alone. Lets say that there is intelligent life out there,and we one day detect a signal. Unfortunately for us the travel distance is simply to grand to overcome. Does that mean that the purpuse of searching is gone? No. Why? let me explain this one to you. KNOWLEDGE. Think about the knowlede we could achieve simply by communicating via our transmitters. It might take eight years to get a response from a potential planet in our closest neighborhood solarsystem, and it might take fourty years for… Read more »
Lawrence B. Crowell
Member
Lawrence B. Crowell
June 6, 2012 2:05 AM
The analysis I did of solar system stability lead to the prospect that only between 100 to 1000 planets in our galaxy may have conditions similar to Earth. This might mean that only that many planets in this galaxy have complex life and ecosystem or biomes. There may be many more planets with microbial ecosystems living on the “margins.” Mars or Europa might be such a place. However only a complex biome-planet could give rise to intelligent life. The probabilities that any of these in our galaxy has intelligent life is pretty small. Out of the 500 million year history of this planet there is only a 100,000 year period with Homo sapiens and two centuries where we… Read more »
Uncle_Fred
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Uncle_Fred
June 8, 2012 9:02 PM

I’m curious LC, what were the parameters that you used to derive that 100-1000 planet figure? In your calculation, what constitutes as Earth-like? Considering an analysis of Kepler results, wouldn’t terrestrial planets be so numerous as to significantly increase the odds of an Earth-Analog?

I thought we were looking at around 50-150 light year radius for such a planet.

Lawrence B. Crowell
Member
Lawrence B. Crowell
June 9, 2012 1:55 AM
This stems from my analysis of the stability of the solar system I did last decade. I ran long term numerical calculations of the three body problem of the Sun, Jupiter and Earth. I found that over a 10,000 year time period there was a drift of the Earth outwards. The orbit of the Earth on a short term basis vibrates about its orbit due to Jovian gravity. The periodicity is not exact, and so there is a chaotic drift that sets in. An analysis of these frequencies leads to a 1/f term that corresponds to this outward drift. This is why I think Earth was around .85AU at its inception and has drifted outwards since. This has… Read more »
Lawrence B. Crowell
Member
Lawrence B. Crowell
June 9, 2012 1:55 AM
This stems from my analysis of the stability of the solar system I did last decade. I ran long term numerical calculations of the three body problem of the Sun, Jupiter and Earth. I found that over a 10,000 year time period there was a drift of the Earth outwards. The orbit of the Earth on a short term basis vibrates about its orbit due to Jovian gravity. The periodicity is not exact, and so there is a chaotic drift that sets in. An analysis of these frequencies leads to a 1/f term that corresponds to this outward drift. This is why I think Earth was around .85AU at its inception and has drifted outwards since. This has… Read more »
VincentFrank67
Guest
VincentFrank67
June 6, 2012 6:31 PM

m y roo mat e’s e x-w ife got p aid $ 15158 the pri or we ek. she is m aking an inc ome on th e lapt op and g ot a $ 5848 00 h ome. A ll she di d was g et fort unate and s et to wo rk the ad vice sh own o n th is we b si te

?????? (C li ck A t My N am e F or L i n k)

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
June 6, 2012 8:18 PM

Testing hypotheses is never a waste of time. Now knowing, which an unfounded claim such as yours on ETI amount to, is certainly a waste of time.

And I say that as one who hypotheses that life naturally will expand to pervasive but unnoticeable forms of biospheres out there (EM silent Oort cloud colonization waves). Still, that needs to be tested like in this instance.

JamesNCleveland
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JamesNCleveland
June 5, 2012 6:04 PM
sangos
Member
sangos
June 5, 2012 6:21 PM

As i read somewhere, our ‘high tech’ VLBI stuff might be like trying to detect smoke signals from advanced civilizations. These guys could be like the predator in the Schwarzenegger movie, who self pack nukes in don’t ask where.

Bill
Member
Bill
June 5, 2012 6:27 PM

I we were to put radio telescopes at the L4 and L5 points, and combine them with radio telescopes on earth, can we say what the potential resolution would be?

By which I mean, how far away could an earth-equivalent (in terms of radio output) planet be and still be confidently detectable?

Zoutsteen
Member
Zoutsteen
June 5, 2012 8:20 PM

I don’t know the math, but there are two different things to be aware of:
1) Resolution: Requires dish separation
2) Signal strength: Requires dish surface area

In other words: two small satelites won’t get the job done which an earth side dish or dish field can also do. But those same two satelites could study strong signals in higher detail.

On earth, dish surface area is artificialy created by using multiple dishes of smaller size. Note that there is now also a plan active to create a large baseline observatory, of which 1 part will be in Australia and the other in South Africa.
see: http://www.universetoday.com/95430/ska-the-worlds-largest-telescope-will-be-built-at-two-sites/

Bill
Member
Bill
June 5, 2012 8:33 PM

ok, so would it be possible to artificially create a large dish at L4 and L5 by flying a ‘fleet’ of three, four, or five smaller satellites spread out over some distance at each point?

krenshala
Guest
krenshala
June 5, 2012 9:40 PM

Leaving out technical details (and difficulties) – Yes, you could create a VLBA “dish” using multiple satellites at the L4/L5 (or other) points.

krenshala
Guest
krenshala
June 5, 2012 9:40 PM

Leaving out technical details (and difficulties) – Yes, you could create a VLBA “dish” using multiple satellites at the L4/L5 (or other) points.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
June 6, 2012 8:41 PM

Planetary Resources may have to make small radio satellites after they have succeeded in the optical satellite market!?

Thomas Houck
Guest
June 7, 2012 4:38 PM
Humans have only existed for a few brief seconds on the age of the Earth clock and for even less time on the age of the Universe clock. The time we have been able to emit radio signals would barely register on these two clocks. Now, apply that to us trying to detect signals from other intelligences and you are basically try to find a microscopic needle in an acres sized haystack. I have no doubt other intelligences exist and are, or have been out there, but at what stage of development. Intelligences that may have reached our level may have long ago come and gone or have yet to reach that level. To assume all intelligences would… Read more »
Geral Bassham
Guest
June 14, 2012 9:35 AM

E T you might see him or her in your own town blending in . next time gary and I have contact we are going to send an invite to dinner . no kidding

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