New research suggests that planets around dying stars could also support life.
Scientists widely believe if life exists beyond the Earth, it would have been in planets orbiting around younger stars like our Sun. This justification seems logical too because so far our solar system is the only place where life has been found. So, the conditions have to be more or less similar to ours own if there is any probability of life existing anywhere else.
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But a new study shows another aspect. It suggests that scientists have to look around the stars of all ages not just young or middle-aged stars if they are searching for inhabitable planets. In about 4 billion years, Sun which is a middle-aged star right now, will get older and swell to about 200 times its current size. It will virtually touch Earth’s orbit and its warmth will turn Earth into an inhabitable planet. Under such hot conditions, the currently frigid locations in our solar system like Pluto, Saturn and Jupiter will eventually warm up and will possibly have just the right temperature to support life in the very distant future.
“Long after our own plain yellow sun expands to become a red giant star and turns Earth into a sizzling hot wasteland, there are still regions in our solar system -- and other solar systems as well -- where life might thrive,” said Lisa Kaltenegger, director of Carl Sagan Institute.
“In the far future, such worlds could become habitable around small red suns for billions of years, maybe even starting life, just like Earth. That makes me very optimistic for the chances for life in the long run.”
Kaltenegger and her colleague Ramses Ramirez modeled the habitable zones of the stars that will run out of fuel and get older and bigger than their normal size. The habitable zone is the region around a star where planet can maintain water on its surface, meaning the planet is warm enough to have water in liquid form, neither frozen nor so hot that the water evaporates and this is the telltale sign that life can thrive there.
Dying stars are typically known as red giants. Red giants are stars that are in the last stage of their stellar evolution and new research provide an in-depth look at how long planets will remain habitable around red giant stars. For instance currently, Earth lies in the habitable zone of the Sun but as the our sun get older and bigger, the Earth will become increasingly warmer and unable to harbor life whereas the colder planets in our solar system will become warm enough to sustain life.
“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system,” said Ramirez. “Currently, objects in these outer regions are frozen in our own solar system and Europa and Enceladus – moons orbiting Jupiter and Saturn –are icy for now.”
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Universe is full of potentially life-sustaining older stars and researchers suggest that scientists should take a closer look at them if they are hunting for alien life.