London, Dec 11 (ANI): A new study has suggested that large and distant ocean worlds could provide a last refuge for life around Sun-like stars, long after the heat of the stars' red giant phase sterilizes closer-in, Earth-like planets.
According to a report in New Scientist, the study was led by Werner von Bloh of the Potsdam Institute for Climate Impact Research in Germany.
Stars similar in mass to the Sun swell to become red giants at the end of their lives, engulfing their inner planets and roasting slightly more distant ones.
The Sun itself is scheduled to enter this phase around 5 billion years from now, which should bake to death any remaining life here even before the planet is swallowed up altogether.
But, new calculations suggest that life could naturally hang on in more remote locales around red giants, reinforcing similar results from an earlier but less detailed study.
The new study focuses on the conditions needed for photosynthesis, including an atmosphere with enough carbon dioxide to support the process, and a temperature that would allow liquid water to exist on the planet's surface.
The team argues that life on planets the size of Earth would die off before the red giant phase begins.
That's because the planet's cooling core would stop the volcanic activity needed to replenish atmospheric carbon dioxide, which is gradually removed by the formation of carbon-containing rocks.
Plants would thus run out of CO2 needed for photosynthesis.
But, the cores of bigger planets, called super-Earths, would stay warm for longer, allowing CO2 to persist in their atmospheres.
Those that start out farther from their parent star than Earth might be frozen during the star's youth and middle-age.
But, they would thaw out later, as the star's habitable zone, where temperatures are right for liquid water, moves outwards as the red giant phase progresses and the star's size and brightness grow.
As for the question that where would a planet have to lie to enjoy habitable conditions for the longest amount of time during this process, the team said the 'sweet spot' would lie a little beyond the orbit of Mars, at around twice the Earth-Sun distance.
An ocean-dominated super-Earth would be best, because it would be best able to hold onto its CO2 atmosphere, the team added. (ANI)