Searching for extraterrestrial life doesn’t stop at oxygen; other key considerations include planet temperature range and its star’s tendency to release radiation that sterilizes it.
Scientists use various instruments, each tailored specifically to one area of life detection, in their search for alien species and life within our solar system (like Mars or Europa ).
Radio Telescopes
Astronomers use radio telescopes to search the sky at different frequencies for signs from another world emitted by stars, planets, galaxies, etc. that emit radio waves part of the electromagnetic spectrum.
Astronomers conducting their search for ET utilize signals emitted by intelligent civilizations, such as television or radar transmissions; these are known as technosignatures, which could give an indication of technology used by these civilizations and even hint at life on other worlds. Astronomers also listen for radio waves emitted by biological organisms which might also serve as indications.
Biosignatures are chemical molecules produced by living things and detectable in their atmosphere or materials. Biological molecules produce specific gases such as carbon dioxide, hydrogen and oxygen that can be observed with telescopes; for this reason astrobiologists are interested in discovering planets containing such atmospheres.
Astronomers use two radio telescopes paired together and pointed toward the same celestial object simultaneously in order to detect biosignature signals. Each telescope is placed a known distance apart on the ground so that any incoming radio waves arrive slightly later at one telescope than at the other and create the signature of a signal.
Astronomers have long searched our solar system for signs of life, yet no rocky exoplanet has been discovered within any star’s habitable zone. Researchers are now concentrating on looking for life beyond our solar system by using spacecraft and ground-based telescopes to detect and study alien planets orbiting other stars – using factors like temperature range or holding liquid water as indicators that life could exist on them.
Infrared Telescopes
Astronomers have spent years searching the skies for radio signals, then expanded their efforts with optical telescopes a decade ago. Today they’re turning their gaze infrared as part of the James Webb Space Telescope’s (JWST) planned launch in 2018. JWST will scour space looking for pulses of infrared light that may indicate extraterrestrial life – and Wright and her team at Dunlap Institute created an instrument specifically tuned towards infrared detection bringing their hands-on SETI work into this new realm.
Infrared radiation is produced by slightly cooler objects than visible light, such as exoplanets and cool clouds of cosmic dust. Furthermore, infrared can pass more easily through dusty regions of space than visible or ultraviolet light, enabling scientists to observe areas otherwise obscured from view.
Hubble has already made significant discoveries using infrared photography. For instance, it has photographed disks of gas and dust where planets are forming around young stars; showing that no two disks look identically.
Astronomers have used this work to better understand how stars and planets form, with many discoveries made regarding young star disks that do not conform to flat planes resembling sprays of debris left from star formation collisions. By employing advanced image processing techniques astronomers have been able to tease out infrared images from archived data that reveal remarkable details about these disks and their contents.
Optical Telescopes
Optic telescopes allow astronomers to directly observe starlight, and capture it to form a spectrum or picture of them. But for planet-hunting astronomers to see any planets orbiting these stars, coronagraphs are needed first as an additional layer of protection against their overwhelming brightness.
Astronomers use what little light remains to search for exoplanets and any signs that might point towards life on them, known as biosignatures in science jargon. If an exoplanet contains high levels of atmospheric gases like oxygen or sulfur, which could indicate that living organisms are constantly replenishing them; similarly water is another essential requirement of life that needs replenishing on a planet-scale.
Astronomers search the universe for signs of life through biosignatures like these biosignature, but must tread carefully when doing so. “It can be like searching for a needle in a haystack,” observes Jill Tarter, one of the pioneering SETI researchers for decades.
Searches for extraterrestrials continue, assisted by new technologies. As members of Congress like Eddie Bernice Johnson (D-Texas) note, astrobiology work has taken on crosscutting themes that make it a central piece of all NASA efforts. The Allen Telescope may prove one of the most powerful tools ever built for this task as it will allow observation of multiple stars simultaneously rather than only single ones as is currently possible with radio telescopes.
Spectrographs
To detect signs of life beyond stars, telescopes must be able to see beyond their overwhelming glare. A spectrograph is one such tool which separates signals into wavelengths similar to how prisms divide white light into its component colors; modern versions usually employ digital circuitry but still utilize this basic principle.
Scientists searching for alien life need to be able to recognize gases produced by living things – like oxygen and methane – found in an atmosphere. However, just finding these gases may not be enough – they must also understand what other signs indicate life may exist on this world – known as its “biosignatures.”
Biosignatures can range from molecules to an ecosystem’s overall “fingerprint,” such as daily length or seasonal variations that make a planet habitable; or it could even be technological signs of civilization.
Locating signs of life will be an enormously daunting challenge. Even with advanced detection technology at our disposal, filtering out interference from terrestrial radio and cellphone transmissions could prove tricky; and to identify any discernible signals within a planet’s atmosphere without becoming distracted by light and heat will require even more sophisticated tools than our current capabilities.
