A team of astronomers has been able to demonstrate that no clear radio signals are emanating from the Gliese 581 planetary system. The red dwarf is estimated to have at least six exoplanets in orbit, one of which was heralded as being potentially habitable. Radio analysis revealed no signs of life.
Investigators conducted this research in 2007, using an imaging method called Very Long Baseline Interferometry (VLBI) to conduct a Search for Extraterrestrial Intelligence-like (SETI) study of the distant worlds. They say that 222 candidate signals were discovered.
However, an automated analysis of the datasets revealed that all of them were in fact caused by interference from Earth's satellites. None was found to actually originate in the intriguing planetary systems. But the team behind the study says that finding alien life was not the purpose of the study.
By confirming that radio signals of the type we're looking for do not originate in Gliese 581, the team was also able to show that VLBI can be used to conduct this type of complex astronomical inquiries. The work was conducted using the Australian Long Baseline Array (ALBA).
Until now, SETI efforts were conducted somewhat randomly, in the sense that radio telescopes were pointed at large swaths of the sky, and astronomers would listen for any incoming signals. If none was found, the telescopes would be aimed at another location.
The research demonstrates that it is possible to use VLBI to target specific star systems, a trait that will come in handy as the search for Earth-analog planets continues. That VLBI was capable of being used in such a directed and targeted search was unknown until now, Astrobiology Magazine
The investigation was led by experts at the Curtin University in Australia, who were coordinated by Hayden Rampadarath, from the CU International Center for Radio Astronomy Research (ICRAR).
ALBA is made up of the Australia Telescope Compact Array (ATCA), the Parkes Observatory and the 22-meter Mopra Telescope. Each of these facilities is located several hundred kilometers away from each other, giving ALBA the highest resolution in astronomy.
The search was focused on frequencies around 1500 megahertz. The Gliese 581 system is located very close to Earth, in the constellation Libra, some 20 light-years away. The observations session lasted for 8 hours, the team says.
The conclusion of the study is that we cannot yet say for certain that life does not exist in the nearby planetary system. What we can be sure of is that VLBI can be used to search for signals of alien intelligence.