Planets around dying stars could harbor life

Simulation of a red giant star surrounded by spiral

When searching for planets that could support life, scientists usually look for Earth-like planets, which orbit around a star, or a life-supporting planet like the Sun. However, according to new research, habitable planets could also be found around dying stars.

In order to identify whether the area around a star is habitable, scientists measure the intensity of the light it releases. In the case of the Sun, a yellow dwarf star, the heat it releases is optimal for sustaining life. However, by the time it will expand into a red giant, it will release more than 4,000 times the light it gives out now.

Astronomer and director of Cornell University‘s Carl Sagan Institute Lisa Kaltenegger and colleagues conducted an experiment aimed at finding out whether planets could support life around planets that are bigger than the Sun. Their findings showed that the observable universe is home to more than 20 stars similar to our Sun that could sustain life. Moreover, they argued that life can be sustained also by the light released by a dying red star.

As explained by Ramses Ramirez, a researcher at Cornell, once a star ages and expands, becoming brighter, the habitable zone is pushed to the outer areas of the solar system. Those areas contain frozen bodies similar to the two frozen moons in our solar system, namely Enceladus and Europa, which orbit Saturn and Jupiter, respectively. According to scientists, they could be the recipients of a level of light and heat that can foster life.

In a couple billion years, our Sun is also expected to expand into a red giant. By then, it will have used almost all hydrogen fuel found at its core. As part of the process, the Sun will swell to about 200 times its current size, expanding until the Earth’s atmosphere, exposing it to its flames. As oceans will boil away due to the extremely high temperatures, life on Earth will be extinguished. However, in the outer parts of the solar system the life-sustaining conditions will be optimal. According to scientists, planets such as Pluto and Charon, its moon, as well as Triton, Neptune’s moon, will offer the most habitable environments. Mercury and Venus though, are expected to be swallowed by the Sun in the process.