Astronomers have used powerful radio telescopes since 1960 to search for alien signals that might provide evidence of advanced civilizations.
According to a recent article in SN Online, most alien beacons may actually be Earthly interference, and large optical telescopes (like Giant Magellan Telescope and Thirty Meter Telescope) coming online in 2020s may miss them altogether.
Large Satellite Dishes
From West Virginia hills to Australia’s flatlands, some of the world’s largest telescopes are searching for evidence of extraterrestrial life using SETI technology. This effort, known as SETI, uses artificial-looking electromagnetic radiation signals that could have come from an alien civilization — known as biosignatures — but this immense data creates difficulties with filtering through. One recent study suggests machine learning, an intelligent form of AI that uses computers to learn things like this could make SETI searches more efficient.
SETI researchers have long focused their antennas on nearby stars in search of alien radio transmissions. But as our understanding of the universe has expanded, their efforts have expanded accordingly. Scientists have discovered thousands of planets outside our solar system which may host life. Astronomers have also created computer models which search for biosignatures such as liquid water, atmospheric oxygen levels or chemical compounds like methane or nitrogen on those planets; all indicators for life.
Astronomers using powerful new telescopes – like the Thirty Meter Telescope and European Extremely Large Telescope – are only capable of detecting strong biosignatures on worlds that have been completely transformed by life, like planets inhabited by ET. Therefore, Loeb has introduced space archaeology – an area within astronomy dedicated to uncovering evidence for ETs.
Large Number of Small Dishes (LNSD)
Searching for alien beacons usually entails scanning large areas of sky, hoping to pick out signals that might otherwise go undetected. But this approach can be both time consuming and inaccurate in its search for signs that may otherwise go overlooked; moreover, it often misses potentially interesting signals – it is also difficult to spot subtle signs of life such as brief, bright pulses of visible light or infrared signatures that advanced civilizations emit.
Astronomers have recently been exploring machine-learning algorithms as a solution for these challenges, testing those that recognize patterns in radio waves and distinguish them from natural interference. Such systems can scan through millions of observations in search of candidate alien signals that might otherwise have gone undetected by humans; training can even improve them at recognizing features typical of Earthly interference that make them better at identifying non-natural signals.
Astronomers use advanced technologies to narrow their searches on planets more likely to support life forms, including rocky planets revolving within a star’s “goldilocks zone”, where temperatures don’t get too hot or too cold for liquid water support. Astronomers also search for planets whose atmosphere could produce gases associated with life such as carbon dioxide, oxygen and methane which plants or animals produce through photosynthesis.
NASA’s James Webb Space Telescope will soon allow astronomers to examine exoplanet atmospheres for chemical compounds produced by life, like chlorophyll pigments that give plants their distinctive infrared light signature and can be detected by sensitive cameras. Scientists can use a technique called vegetation red edge to search distant exoplanets for these chemicals that may reveal extraterrestrial biosphere signatures.
Radio Telescopes
Astronomers utilize various technologies to detect radio waves. While visible light travels at lightspeed, radio waves have much longer wavelengths of several centimeters to several kilometers; therefore they can be picked up over long distances without reflection by atmospheres or planet surfaces, and can therefore be picked up over great distances from objects like stars, galaxies, quasars, pulsars and planets emitting radiation that astronomers collect using large satellite dishes called radio telescopes that contain receivers designed to collect radiation while amplifying and then converting this radiation into data stored magnetic disks for computer processing.
Astronomers use computers capable of performing calculations at submillisecond speeds – up to 16 quadrillion operations per second! This way, their results can be compared with existing data and interpreted for signs of life.
One form of star search involves looking for evidence of waste heat generated by civilizations in distant stars. This search relies on the assumption that intelligent life would use huge structures around their star to capture most of its energy and avoid burning it up, leaving an excess of infrared radiation detectable through detection techniques such as Kepler data sets such as Tabby’s Star. Penn State astronomers have conducted extensive study of such a star in Kepler data set known as Tabby’s Star.
Optical Telescopes
Since the dawn of civilization, people have long speculated whether life exists beyond our planet. In search of alien life forms, various technologies have been devised – including 42 radio telescopes comprising California’s Allen Telescope Array and Chile’s forthcoming European Extremely Large Telescope at Paranal Observatory – designed specifically to detect radio signals that travel farther without becoming scattered or absorbed by objects in their path.
Recently, astronomers have begun searching for other signals of intelligence. Such “technosignatures” might include chemical composition of planet atmospheres and laser emissions as possible indicators of alien civilizations. Penn State astronomers led by Jason Wright (link is external) have conducted similar searches. One specific area they investigated involved Dyson spheres – giant artificial structures designed to capture light while emitting very little radiation waste heat – that might indicate their existence.
Astronomers have also looked for “biosignatures” produced by living organisms, such as carbon dioxide, water vapor and unbound oxygen. Telescopes that can observe planets as they pass in front of their host stars may detect changes in atmospheric levels of these gases produced by life; for instance, James Webb Space Telescope can detect changes.
