Astronomers discover two planets with oceans 500 times deeper than Earth's
In December 2022, astronomers announced the discovery of two exoplanets whose oceans are up to 500 times deeper than those of Earth.
In the news : astronomers made this discovery by measuring the density of planets.
The planets in question orbit a red dwarf, Kepler-138, a small star located some 218 light-years from Earth. They were discovered by combing through data from the Hubble and Spitzer space telescopes.
The researchers published their findings on December 15, 2022 in the journal Nature Astronomy. A free version of the preprint is available on the arXiv online database .
In the study, they describe the two planets, Kepler-138 c and Kepler-138 d. They seem to have oceans more than 1,600 kilometers deep, 500 times deeper than the average on our blue planet.
In our solar system, nothing like this has ever been seen. Only a handful of moons, including Europa , could have deep oceans under an ice cap, but those of the planets in question do not.
?How were the oceans discovered
The background : Using data from space telescopes, scientists have been able to discover that planets have unusual properties.
These two celestial bodies are larger than the Earth, but much less dense. However, their density is not low enough to speak of gas giants.
This means that a significant fraction of their mass is made up of water. The amount of water on Earth, for example, compared to the amount of other matter, is actually not very large.
Only 0.05% of the Earth is made up of water. Most of this water is on the surface, covering about 70% of the territory.
The oceans of the two planets could be very different from those of Earth. They would probably be very hot and under great pressure. It is even possible that there is no real boundary between the ocean and the atmosphere. The two would blend into each other.
The top of the atmosphere may consist of vapour. Deeper, the pressure could be high enough for liquid water.
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