The new study, which was authored by researchers with NASA’s Jet Propulsion Laboratory and the California Institute of Technology, is based on the Drake equation and examined where and when other intelligent life forms may have lived or be living in the cosmos.
Researchers took into consideration a variety of factors that would influence the development of alien life, such as the frequency of radiation-emitting supernovas, the time needed for intelligent life to evolve and the potential tendency for civilizations to destroy themselves, as well as the prevalence of sun-like stars harboring Earth-like planets.
With a model in hand, officials determined that intelligent life was most likely to emerge about 8 billion years after the formation of the Milky Way, noting that the likelihood of such life surfacing peaked at about 13,000 light-years from the galactic center.
By comparison, Earth, which sits some 25,000 light-years from the galactic center, saw humans emerge roughly 13.5 billion years after the formation of the Milky Way.
“As we cannot assume a low probability of annihilation, it is possible that intelligent life elsewhere in the galaxy is still too young to be observed by us,” researchers concluded in their study. “Therefore, our findings can imply that intelligent life may be common in the galaxy but is still young, supporting the optimistic aspect for the practice of [search for extraterrestrial intelligence].”
However, the researchers also found that the potential for self-annihilation was “highly influential in the quantity of galactic intelligent life,” with officials speculating that “if intelligent life is likely to destroy themselves, it is not surprising that there is little or no intelligent life elsewhere.”
The researchers suggested that such self-annihilation may have resulted from war, climate change or the development of biotechnology, all possibilities cited in studies dating back to the early 1960s.
The study, which was published in the arXiv database, has been submitted to a journal and is set to be peer-reviewed. The report comes after a team of scientists from the University of Nottingham estimated that there were 36 communicating, intelligent, alien civilizations in the Milky Way.