Super-Earths may remain habitable for tens of billions of years

(ORDO NEWS) — If massive planets are at a decent distance from their star, they can retain an atmosphere and water for an incredibly long time. If they were thrown out of the parent system, then longer than the existence of the Universe.

Conditions on Earth became suitable for life a few billion years ago, and in a few billion years it will again become uninhabitable. However, some exoplanets, massive super-Earths, are theoretically capable of sustaining life for much longer, sometimes more than 80 billion years.

Super-Earths are called large exoplanets with a solid surface weighing up to 10 Earth masses – many times larger than ours, but smaller than those of small gas planets like Neptune. There are no super-earths in the solar system – perhaps Jupiter prevented the appearance of such a planet , “swallowing” its embryo.

However, telescopes are detecting quite a few super-Earths around other stars in the Milky Way. Mol Lous and her colleagues at the University of Zurich (Switzerland) considered a subclass of “cold super-Earths” that rotate at a decent distance from their stars and maintain a moderate temperature.

Calculations show that such cool worlds are able to hold the primary atmosphere (consisting mainly of hydrogen and helium) for billions of years, and its density is 100-1000 times greater than Earth’s.

Under this dense shell, liquid water can exist on the surface, and new simulations have shown that it can persist for a very long time, more than long enough for the emergence and development of life.

It is worth noting that the search for exoplanets is usually based on changes in the brightness or exact position of the star, which are caused by the rotation of a nearby planet.

Therefore, most of the super-Earths found by telescopes have rather close orbits, and the new study was carried out theoretically – without observations, using only mathematical models. Swiss astronomers have run over a thousand simulations of the evolution of super-Earths of varying masses, atmospheres, and orbits around solar-type stars.

The work showed that too close an orbit leads to gradual erosion and loss of the atmosphere under the influence of a stream of stellar wind particles.

However, at a sufficient distance – greater than the orbit of Mars in the solar system – the hydrogen-helium atmosphere can not only persist for a long time, but also heat the planet due to the greenhouse effect.

Scientists estimate that the super-Earth can remain in this state for five to eight billion years, until its parent star approaches the last stages of life and begins to turn into a red giant.

However, more exotic options are also possible. A random game of gravity is capable of throwing the super-Earth away from its mother system and sending it flying free as an “orphan planet” with no connection to any star.

Calculations suggest that with enough mass (10 Earths) and a sufficiently dense atmosphere, such a lone super-Earth could potentially remain habitable for an incredible 84 billion years. This period far exceeds the age of our Universe and the entire period during which stars will exist in it.

Life on a free-flying super-Earth must be very different from ours. If it developed on such a planet, then it adapted to its conditions, completely different from those on earth, with the absence of light and enormous atmospheric pressure.

However, almost isolated ecosystems are known on our planet that exist in similar conditions, for example, among “black smokers” at the bottom of the oceans. The main source of energy for local organisms is not photosynthesis, but chemosynthesis, and they do not need light.

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