A newly published study suggests the Milky Way galaxy could contain alien civilizations, though there's a strong possibility most of them are already dead.

Researchers from the California Institute of Technology, NASA's Jet Propulsion Laboratory, and Santiago High School used an expanded version of the famous Drake Equation, which determined the odds of extraterrestrial intelligence existing in our galaxy. The study looked at various factors that could presumably lead to a habitable environment, and determined intelligent life may have emerged in our galaxy about 8 billions years after it was formed. Some of these civilizations could have been 13,000 light-years from the galactic center, about 12,000 light-years closer than Earth, where humans are believed to have emerged 13.5 billion years after the Milky Way was formed.

The study, which has yet to be peer reviewed, also considered factors that may have ended these civilizations, such as exposure to radiation, a halt in evolution, and the tendency for intelligent life to self-annihilate, whether it be through climate change, technological advancements, or war. This suggests that any alien civilizations that are still alive are most likely young, as self-annihilation would presumably occur after a long period.

"While no evidence explicitly suggests that intelligent life will eventually annihilate themselves, we cannot a priori preclude the possibility of self-annihilation," the study read. "As early as 1961, Hoerner (1961) suggests that the progress of science and technology will inevitably lead to complete destruction 11 and biological degeneration, similar to the proposal by Sagan and Shklovskii (1966). This is further supported by many previous studies arguing that self-annihilation of humans is highly possible via various scenarios (e.g., Nick, 2002; Webb, 2011), including but not limited to war, climate change (Billings, 2018), and the development of biotechnology (Sotos, 2019)."