SETI Just Searched 10 Million Stars For Alien Civilizations

Following the results of our previous low frequency searches for extraterrestrial intelligence (SETI) using the Murchison Widefield Array (MWA), directed toward the Galactic Centre and the Orion Molecular Cloud (Galactic Anticentre), we report a new large-scale survey toward the Vela region with the lowestupper limits thus far obtained with the MWA. Using the MWA in the frequency range 98-128 MHz over a 17 hour period, a 400 deg2 field centered on the Vela Supernova Remnant was observed with a frequency resolution of 10 kHz.

Within this field there are six known exoplanets. At the positions of these exoplanets, we searched for narrow band signals consistent with radio transmissions from intelligent civilizations. No unknown signals were found with a 5σ detection threshold. In total, across this work plus our two previous surveys, we have now examined 75 known exoplanets at low frequencies.

In addition to the known exoplanets, we have included in our analysis the calculation of the Effective Isotropic Radiated Power (EIRP) upper limits toward over 10 million stellar sources in the Vela field with known distances from Gaia (assuming a 10 kHz transmission bandwidth). Using the methods of Wright et al. (2018) to describe an eight dimensional parameter space for SETI searches, our survey achieves the largest search fraction yet, two orders of magnitude higher than the previous highest (our MWA Galctic Anticentre survey), reaching a search fraction of ∼ 2×10−16. We also compare our results to previous SETI programs in the context of the EIRPmin – Transmitter Rate plane.

Our results clearly continue to demonstrate that SETI has a long way to go. But, encouragingly, the MWA SETI surveys also demonstrate that large-scale SETI surveys, in particular for telescopes with a large field-of-view, can be performed commensally with observations designed primarily for astrophysical purposes.