ASTRON: alien civilisations rare or absent in the local Universe

15 September 2015

Sensitive new telescopes now permit astronomers to detect the waste heat that is expected to be a signature of advanced alien civilisations that can harness enormous energies on the scale of the stellar output of their own galaxy. Professor Michael Garrett, General & Scientific director of NWO-division ASTRON, has used radio observations of candidate galaxies to show that such advanced civilisations are very rare or entirely absent from the local Universe. The main results will be presented this week as a letter in the European journal Astronomy & Astrophysics.

Astron Dyson Swarm. Credit: Astron.Astron Dyson Swarm. Credit: Astron.

Advanced civilisations harnessing energies on galactic scales (so-called Kardashev Type III civilisations) are expected to be detectable in the mid-Infrared part of the spectrum via the emission of significant waste heat products. A team of astronomers led by Dr. Jason Wright (Penn State University, USA) has already drawn up a list of several hundred candidate galaxies (culled from a total population of 100,000 objects) where unusually extreme mid-IR emission is observed. One problem is that although rare, this kind of emission can also be generated by natural astrophysical processes related to thermal emission from warm dust.

Professor Michael Garrett 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.

'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!', said Garrett.

Source: ASTRON Netherlands Institute for Radio Astronomy