To find extraterrestrial life, follow the trial of radiation.

Scientists in Germany believe that they have found the most likely star systems to host alien organisms.

Oxygen-rich planets hosted by stars with relatively fewer metals are more likely to be habitable for life, according to a new analysis by a team of astronomers from the Max Planck Institute for Solar System Research.

Stars with a low proportion of metals — that is, elements heavier than hydrogen and helium — are known to emit more radiation than those with a high metallicity. Yet, compared to planets attached to high-metal hosts, those orbiting low-metal stars are equipped with an even thicker ozone layer thanks to the beneficial interplay between oxygen and ultraviolet radiation, according to the study’s press release.

As observed here on Earth, a robust ozone layer is critical to shield against UV radiation, which damages DNA and thwarts the evolution of living organisms.

Meanwhile, there are many elements that can affect the UV output of a star, including its temperature, metal content and distance from orbiting planets.

Traditionally, scientists have studied Earth-like worlds that orbit metal-rich stars because they are in the same category as our Sun. However, this study, published on Tuesday in Nature Communications, is the first to consider the role of UV radiation on the potential habitability of planets.

To perform the study, a team of researchers led by astronomer Anna Shapiro and her team of astronomers replicated different Earth-like worlds that orbited Sun-like stars and adjusted the parameters that would affect the UV radiation.

They found that metal-rich stars emit “substantially less” UV radiation than stars with fewer metals, resulting in planets with weaker ozone and thus, “paradoxically” greater UV exposure, researchers said. “Therefore planets in the habitable zones of stars with low metallicity are the best targets to search for complex life on land.”

In other alien news, one self-proclaimed time traveler alleged this past March that “hostile” extraterrestrials are coming to earth.

And, last December, Nicolas Cage admitted that he was actually an alien as a child.