Water was once thought to be unique to Earth, mostly because the technology to find it didn't exist. Now scientists have shown that water is likely a major part of exoplanets in the galaxy. Exoplanets are planets that orbit other stars can range anywhere from two to four times the size of Earth. This new watery outlook may have huge implications for the search for extraterrestrial life in our Galaxy.
Exoplanets were first discovered orbiting other stars in 1992 and ever since there has been an interest in learning what exactly these planets are made of and whether they are suitable for life. A new evaluation of data from the Kepler Space Telescope and the Gaia mission shows that many of the known planets could be composed of as much as 50% water. With the Earth being just 0.02% water by weight, this data would sure seem to mean those other exoplanets are indeed water-worlds.
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Lead researcher Dr. Li Zeng at Harvard University said of the discovery, "It was a huge surprise to realize that there must be so many water-worlds." Out of the 4,000 confirmed or possible exoplanets discovered so far, about half are 1.5 times the size of Earth, and another half is about 2.5 times the radius. This new research being conducted by a group of international scientists is analyzing the exoplanets with mass measurements and recent radius measurements from the Gaia satellite to speculate on their internal contents.
Li Zeng added, "We have looked at how mass relates to the radius and developed a model which might explain the relationship. The model indicates that those exoplanets which have a radius of around x1.5 Earth radius tend to be rocky planets (of typically x5 the mass of the Earth), while those with a radius of x2.5 Earth radius (with a mass around x10 that of the Earth) are probably water worlds." Just because these water-worlds may be composed of half water, it doesn't mean they look like Earth's watery surface.
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"This is water, but not as commonly found here on Earth," Li Zeng explained. "Their surface temperature is expected to be in the 200 to 500 degree Celsius range. Their surface may be shrouded in a water-vapor-dominated atmosphere, with a liquid water layer underneath. Moving deeper, one would expect to find this water transforms into high-pressure ices before we reaching the solid rocky core. The beauty of the model is that it explains just how composition relates to the known facts about these planets."
<blockquote class="twitter-tweet" data-lang="en"><p lang="en" dir="ltr">Eord Flyuae BG-V d3-6620. Three very different water worlds in this system. Proceeding to take atmospheric gas samples. <a href="https://t.co/D9uwmQggEe">pic.twitter.com/D9uwmQggEe</a></p>— Commander Kilbreck (@CmdrKilbreck) <a href="https://twitter.com/CmdrKilbreck/status/1030723717788258304?ref_src=twsrc%5Etfw">August 18, 2018</a></blockquote>
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"Our data indicate that about 35% of all known exoplanets which are bigger than Earth should be water-rich," Li Zeng said. "These water worlds likely formed in similar ways to the giant planet cores (Jupiter, Saturn, Uranus, Neptune) which we find in our own solar system. The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up. The next generation space telescope, the James Webb Space Telescope, will hopefully characterize the atmosphere of some of them. This is an exciting time for those interested in these remote worlds."
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