Posted by Gonzo on August 25, 2023 4:16 PM
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Scientists use biosignatures – an approach known as “biosignature analysis” – to search for signs of life on planets distant from Earth. Such methods could reveal evidence of alien life forms on distant worlds.
No telescope exists that is designed specifically to image exoplanets directly, and biosignature searches must compete with other branches of astronomy for observing time. Eventually, researchers hope to build one specifically dedicated to exoplanet research.
Radio Telescopes
Astronomer Jill Tarter first became fascinated with searching for life beyond Earth as a child while exploring western Florida beaches with her father and gazing up at the stars. Since then, Tarter has spent her time at SETI Institute scanning radio frequencies for signs that aliens might be trying to communicate with us.
Telescopes can detect light and heat waves, as well as being equipped with receivers capable of picking up radio signals from an extraterrestrial civilization. Such signals could take the form of radio or radar waves, television or laser transmissions or cosmic microwave background radiation.
Astronomers use correlators – computers with antenna arrays connected by wires – to identify any possible signals, using hundreds of views per object every minute at speeds femtoseconds. Special software developed by both astronomers and computer engineers turns this data into maps of the sky that show how much of each object’s light reflects or emits radio waves.
Astrobiologists’ ultimate goal is to directly image planets. This requires blocking out starlight so as to reveal a planet’s dark surface through an approach known as internal imaging; such efforts have thus far relied on luck for success; alternatively, an interstellar probe such as Breakthrough Starshot would launch thousands of tiny spacecrafts at high speeds to search for biosignatures on nearby planets.
Optical Telescopes
Astronomers search not only for radio signals that might indicate intelligent life; they’re also searching for “biosignatures,” molecules and particles that might signal that an alien planet contains living organisms. Such searches require complex investigations involving multiple lines of evidence; for instance, if scientists discover unusual atmospheric gases-such as oxygen-in an alien planet’s atmosphere, such as volcanoes emitting it or photosynthesis occurring on its surface creating it, scientists need to know where that gas came from in order to understand where it came from and how it got there from before conclusively making conclusions on whether that planet does indeed harbor life or not.
Finding out whether there are terrestrial exoplanets requires getting an unobstructed view, which requires blocking out their star’s intense light glare. Ground-based telescopes equipped with coronagraphs are effective tools for this, while NASA’s Wide Field Infrared Survey Telescope, due for launch sometime around mid-2028, will offer another perspective that allows researchers to search star systems without being blinded by starlight for signs of terrestrial planets.
As part of our search for extraterrestrial life, astronomers should focus on studying exoplanets that orbit close to Earth such as our solar system. This will enable astronomers to study planets with more atmospheric depth as well as complex gases like carbon dioxide and water more closely; eventually allowing scientists to detect signs that such molecules exist as well as what power source drives their production.
Infrared Telescopes
Astronomers searching for signs of life on exoplanets typically look for biosignatures; chemicals like water, ozone and methane produced by living things; as well as technosignatures produced by alien technology like radio or TV signals or lasers.
Astronomers use infrared telescopes to study celestial objects that do not emit visible or ultraviolet light, such as planets. Planets emit infrared radiation, and scientists have already used infrared telescopes like NASA’s Spitzer space telescope to observe it and identify features on distant planets like Jupiter’s south pole cyclones, an enormous ring around Saturn, and a dark, dusty cloud near Proxima Centauri’s orbit.
Astronomers need direct light from distant worlds in order to see them, creating spectrum or images of them. Unfortunately, ground-based telescopes often cannot do this effectively enough. Astronomers have developed coronagraphs as a solution – specifically masking out stars so nearby objects can be seen – while ultimately any space telescope searching for Earth-like planets must also have this capability.
Biosignature searches compete for telescope time with other astronomy goals; researchers continue to wish for an exoplanet-imaging space telescope similar to what NASA initially imagined for their Terrestrial Planet Finder mission.
Ground-Based Telescopes
Astronomers may use ground-based telescopes to search for alien life, but finding any evidence will likely be challenging due to distance. “There won’t be one definitive sign,” states Seth Shostak of the SETI Institute, “instead there will likely be multiple pieces of circumstantial evidence called biosignatures that hint at its presence.
Example: A rocky planet in the habitable zone around a sunlike star with high levels of oxygen, carbon, nitrogen, phosphorus, sulfur and hydrogen that cannot be explained through nonbiological processes may contain life. Finding such an instance would require blocking out the starlight and seeing its light form an image or spectrum; to accomplish this most efficiently is using an interstellar telescope like NASA’s proposed James Webb Telescope or European Extremely Large Telescope replacement to access space-based telescopes like these ones.
These space telescopes feature mirrors up to 6.5 meters across that can collect light frequencies and wavelengths over an extensive spectrum. Furthermore, special tools like coronagraphs and starshades must also be available that precisely obscure starlight in order to reveal planets around that star – as well as being capable of operating at distances where scientists believe exoplanets may exist.
