If you have "discover an alien civilization" on your 2020 bingo card, you're going to have to wait a little longer to cross it off. A new large-scale survey of the sky looked into the dark forest of the cosmos, examining over 10 million stars, but failed to turn up any evidence of alien technologies.
The study, published in Publications of the Astronomical Society of Australia on Monday, details a search for extraterrestrial intelligence (SETI) using the Murchison Widefield Array (MWA), a collection of 4096 antennas planted in the red soil of Western Australia that detects radio signals from space. "They are little spider-like antennas that sit on the ground," explains Chenoa Tremblay, co-author on the study and astrophysicist with CSIRO, an Australian government scientific research organization.
Tremblay and co-author Stephen Tingay, from the International Centre for Radio Astronomy Research, used the MWA to listen out for "technosignatures," or evidence of alien technology, in a portion of the sky around the Vela constellation. Tremblay explains this region is scientifically interesting because a large number of stars have exploded and died, creating ideal conditions for new stars to form. The search for extraterrestrial life "piggy-backs" on other work studying this region to understand the life cycle of stars.
But how can you tell a radio signal from space is coming from an alien civilization? "Think of a car alarm when you leave your lights on, where there are a series of equally spaced 'ping' sounds," Tremblay says. The survey looks for a repeating ping that may be escaping noise from a planet or "a purpose built signal."
After listening to the Vela region for 17 hours, no unknown signals were detected. While the survey was able to capture over 10.3 million stellar sources and contained six known exoplanets (likely many more exist in the region), the team notes it was like trying to find something in an ocean, but only studying "a volume of water equivalent to a large backyard swimming pool."
And there's another big caveat.
"Looking for technosignatures is assuming that the civilisation have technology similar to our own," says Tremblay.
Intelligent life may not have developed the ability to communicate via radio signals, she notes. Part of her work also examines where simple molecules required for life come from and how we might be able to detect them. If we can find signals of these molecules, it may signal alien life -- just not the kind we're used to in Hollywood blockbusters.
A deeper look at the Galactic Center may be on the cards, a region of space the team has examined before. Because the search for life is performed in conjunction with other science experiments, Tremblay says "where we go next will depend on the other science."
And that's an encouraging sign for SETI. It may be like looking for a single leaf in a dark forest, but by doing this work in conjunction with other science and and astrophysical investigations, the cosmos is slowly revealed to us.
On Sept. 2, researchers published a "breakthrough" which could help narrow the search for intelligent life in our home galaxy, the Milky Way. Astronomers, from the University of Manchestor and the Breakthrough Listen collaboration, reanalyzed data and placed new constraints on radio transmissions coming from within the Milky Way. The new constraints helps us to more clearly pinpoint where we should be listening: The new data shows less than 0.04% of star systems would be able to host an alien civilization with technology we could detect.
And life may have even existed closer to home. NASA's Perseverance rover and China's Tianwen-1 mission are both currently en route to Mars with the capability of searching for life on the red planet. They are expected to reach Mars by February 2021.