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 extremely extended baseline interferometers (VLBIs), the most significant boast an angular resolution some two orders of magnitude far 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 right here.
What tends to make Gliese 581 intriguing is its planets, which incorporate two superEarths that most likely sit on the edge of their habitable zone.
That helps make them good candidates for life. And if this life is anything like our own, it might currently be broadcasting at radio frequencies that we can tune in to.
Despite the fact that VLBI has extraordinary angular resolution, it has by no means been used to look for signs of extraterrestrial intelligence. So this is an important proof-of-principle stage.
The Australian instrument, identified as the Australian Lengthy Baseline Array, consists of three radio telescopes a couple of hundred kilometres apart, which provides them an angular resolution that is about the very same as Hubble’s.
Rampadarath and pals pointed it at Gliese 581 for a complete of 8 hrs in June 2007, tuning into frequencies close to 1500 megahertz. Why they’ve waited so lengthy to publish their result, they do not say but their paper has now been accepted for publication in The Astronomical Journal.
What they discovered is fascinating. VLBI methods turn out to be helpful for SETI searches due to the fact they immediately exclude several terrestrial sources of interference that might otherwise look like SETI signals. That is since the very same signals have to show up at all the telescopes a number of hundred kilometres apart.
In total, Rampadarath and co found 222 candidate SETI signals. Nonetheless, they were able to exclude all of these relatively simply using automated evaluation strategies, which have become increasingly sophisticated in recent years. (That’s partly since of tasks such as SETI@Property which has located billions of intriguing signals, all of which have turned out to be false alarms.)
The false alarms picked up by the Australian Long Baseline Array possibly came kind Earth orbiting satellites, say the group.
Of course, this does not 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.
As an alternative, it locations limits on the strength of these signals and not specifically 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 likelihood that Gliese inhabitants had been broadcasting immediately to Earth making use of an Arecibo-type dish, Rampadarath and co would have very easily picked up the signal. (Arecibo is a 300 metre radio telescope in Puerto Rico).
On the other hand, the ordinary radio transmissions like individuals we continually broadcast into space, would have been far as well weak to be picked up by the Australian team.
That is not to say that this kind of observation will not be feasible in long term. The Australian array is by no means the largest of most sensitive instrument accessible today.
What is far more, astronomers are preparing a new VLBI telescope known as the Square Kilometre Array which will have the sensitivity to choose 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 about exoplanets that sit in their habitable zones (that means they’re warm adequate for liquid water). These places are of intense interest.
Time on VLBI telescopes is treasured and hard to come by. But the prize here is of virtually incalculable value–the discovery of intelligent life past the Solar System.
So it wouldn’t be a comprehensive shock if radio astronomers identified methods to hunt far more often for radio broadcasts from new and exciting exoplanets.