Breakthrough Listen, an effort to listen for radio signals from alien civilizations that, plans to devote significant time this year observing Tabby’s star to see if an alien mega-structures are causing that star’s unexplained dimming.
While Siemion and his colleagues are skeptical that the star’s unique behavior is a sign of an advanced civilization, they can’t not take a look. They’ve teamed up with UC Berkeley visiting astronomer Jason Wright and Tabetha Boyajian, the assistant professor of physics and astronomy at Louisiana State University for whom the star is named, to observe the star with state-of-the-art instruments the Breakthrough Listen team recently mounted on the 100-meter telescope. Wright is at the Center for Exoplanets and Habitable Worlds at Pennsylvania State University.
The observations are scheduled for eight hours per night for three nights over the next two months, starting Wednesday evening, Oct. 26. Siemion, Wright and Boyajian are traveling to the Green Bank Observatory in rural West Virginia to start the observations, and expect to gather around 1 petabyte of data over hundreds of millions of individual radio channels.
The uncertainty of science: A new analysis of old star data has concluded that KIC 8462852, also known Tabby’s Star and subject to random fluctuations that no scientist can explain, has not dimmed by 20% in the past century.
This reduces the chances that the fluctuations are caused by the slow accumulating construction of a Dyson sphere by an alien civilization, as some have proposed, but it still does nothing to explain the star’s random changes in brightness.
Worlds without end: In order to increase the odds of contacting extraterrestrial civilizations, astronomers have calculated the area in the sky where an alien-built Kepler could have seen the Earth transit the sun, thus increasing the chances that those alien-astronomers have discovered Earth and have tried to contact us.
“The key point of this strategy is that it confines the search area to a very small part of the sky. As a consequence, it might take us less than a human life span to find out whether or not there are extraterrestrial astronomers who have found the Earth. They may have detected Earth’s biogenic atmosphere and started to contact whoever is home,” explains René Heller from the MPS.
Not every star is equally well suited as a home of extraterrestrial life. The more massive a star, the shorter is its life span. Yet, a long stellar life is considered a prerequisite for the development of higher life forms. Therefore the researchers compiled a list of stars that are not only in the advantageous part of the sky but also offer good chances of hosting evolved forms of life, that is, intelligent life. The researchers compiled a list of 82 nearby Sun-like stars that satisfy their criteria. This catalogue can now serve as an immediate target list for SETI initiatives.
The uncertainty of science: Two weeks of targeted observations by the Allen Telescope Array in California have detected no clear signal of an alien civilization at the star KIC 8462852 where Kepler observations have seen variations that could possibly be caused by giant alien structures.
Two different types of radio signals were sought: (1) Narrow-band signals, of order 1 Hz in width, such as would be generated as a “hailing signal” for societies wishing to announce their presence. This is the type of signal most frequently looked for by radio SETI experiments. (2) Broad-band signals that might be due to beamed propulsion within this star system. If astroengineering projects are really underway in the vicinity of KIC 8462852, one might reasonably expect the presence of spacecraft to service this activity. If these craft are propelled by intense microwave beams, some of that energy might manifest itself as broad-band radio leakage. “This is the first time we’ve used the Allen Telescope Array to look for relatively wide-band signals, a type of emission that is generally not considered in SETI searches,” said SETI Institute scientist Gerry Harp.
Analysis of the Array data show no clear evidence for either type of signal between the frequencies of 1 and 10 GHz. This rules out omnidirectional transmitters of approximately 100 times today’s total terrestrial energy usage in the case of the narrow-band signals, and ten million times that usage for broad band emissions.
The data shows no sign of alien civilization, but it also does not eliminate the possibility. More detailed observations are required to do that.
New observations of the best candidate galaxies now suggests that very advanced civilizations are very rare or don’t exist in the local universe.
They looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation, which could possibly be produced as the waste heat from civilizations using energy on galactic scales.
Professor Michael Garrett (ASTRON & University of Leiden) has used radio measurements of the very best candidate galaxies and discovered that the vast majority of these systems present emission that is best explained by natural astrophysical processes. In particular, the galaxies as a sample, follow a well-known global relation that holds for almost all galaxies – the so-called “Mid-Infrared Radio correlation”. The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust – for example, dust generated and heated by regions of massive star formation.
As Professor Garrett explains: “the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilisations basically don’t exist in the local Universe. In my view, it means we can all sleep safely in our beds tonight – an alien invasion doesn’t seem at all likely!”.
Joking aside, Professor Garrett is still looking at a few candidate galaxies that lie off of the astrophysical correlation: “Some of these systems definitely demand further investigation but those already studied in detail turn out to have a natural astrophysical explanation too. It’s very likely that the remaining systems also fall into this category but of course it’s worth checking just in case!”
Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume.