Expanding red giants can unlock life on frozen planets, study finds
As a star like our Sun gets older, it expands to become a Red Giant, and new research from Cornell scientists has found that frozen worlds in the outer part of a solar system could become habitable once their sun swells in size.
Planetary researchers are particularly focused on habitable zones, or the sphere of space around a star that receives just the right amount of light and energy to sustain life as we know it. Published in The Astrophysical Journal, the new research modeled the habitable zones for aging stars and how planets have in this life-giving part of space.
“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system,” study author Ramses M. Ramirez, research associate at Cornell’s Carl Sagan Institute, said in a news release. “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.”
Credit: Cornell University
Planets and their moons sit in the habitable zone of a Red Giant for up to 9 billion years. Earth, on the other hand, has been hanging around in the Sun’s habitable zone for approximately 4.5 billion years, and it has hosting many different versions of life.
However, in several billion years the Sun will grow to swallow Mercury and Venus, and turn Earth and Mars into hot, rocky planets. It will also warm remote worlds like Jupiter, Saturn and Neptune, as well as their moons – possibly to the point of sparking new life.
“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 study author Lisa Kaltenegger, associate professor of astronomy and director of the Carl Sagan Institute.
“For stars that are like our sun, but older, such thawed planets could stay warm up to half a billion years in the red giant habitable zone. That’s no small amount of time,” Ramirez added.
“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 noted.
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Image credit: NASA
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