[Introduction] University of Montreal A research team found evidence of water on extraterrestrial planets. Researchers found that two exoplanets orbiting an red dwarf star are the "water world": water makes up the majority of the entire planet. These two water planets, , are located in the galaxy system 218 light years away from Earth. They are different from any planet found in our solar system.
This team, led by Caroline Pialette of the Trottier Institute of Exoplanetary Studies at the University of Montreal, published a detailed study of the Kepler-138 planetary system in today's journal Natural Astronomy.
![[Introduction] A research team at the University of Montreal found evidence of water on the outside world. Researchers have found that two exoplanets orbiting a red dwarf are the](https://cdn-dd.lujuba.top/img/loading.gif)
Red planet is the star Kepler-138b
Pialette and his colleagues used Hubble Telescope and the retired Spitzer Telescope to observe exoplanets Kepler-138c and Kepler-138d, and found that these planets may be composed primarily of water.
These two planets and a smaller planet companion are closer to the star Kepler-138b. Kepler 138b was discovered by NASA's Kepler Space Telescope . The new study also found evidence of the existence of a fourth planet.
Instead of directly discovering water on Kepler-138c and D, astronomers use models to compare the size and mass of planets and conclude that a large portion of their volume – up to half – should be composed of matter that is lighter than rock but heavier than hydrogen or helium (making up a large number of gas giant planets, like Jupiter ), and the most common of these candidate materials is water.
"We used to think that these planets that are a little bigger than Earth are made of metal and rock like Earth, which is why we call them super Earth," explains Bjorn Benneck, a professor of astrophysics at the University of Montreal and co-author of the paper. "However, we have now proven that these two planets, Kepler-138c and D, are essentially completely different, and a large portion of their entire volume is likely to be made of water. This is the best evidence for the existence of the water world so far. This is the theoretical recognition by astronomers have been around for a long time."
Planets c and planet d have more than three times the volume of Earth, and are twice as large as Earth's mass, and have a much lower density than Earth. This is surprising because most of the planets slightly larger than Earth that have been studied so far seem to be rocky worlds like ours.
"Imagine the advanced version of Europa or Enceladus , these water-rich satellites orbit around Jupiter and Saturn , but will bring them closer to the stars," Piulet explained. "They will have huge water vapor claddings, not surfaces with ice."
water planets structure
researchers also reminded, "The surfaces of these planets may not have oceans like those on Earth. The temperature of the Kepler-138d atmosphere is likely to be higher than the boiling point of water, and we expect that the planet will have a high-density atmosphere composed of steam. Only under the steam can there be high-pressure liquid water, or even another stage of water at high pressure, called supercritical fluid."
In 2014, based on data from NASA's Kepler Space Telescope, allowed astronomers to announce the detection of three planets orbiting Kepler-138. This is derived from measuring the descent of starlight when the planet temporarily passes through the star. Betnik and his colleague Diana Dragomir from the University of New Mexico came up with the idea of re-observing the planetary systems through the Hubble and the Spizzer space telescope in order to capture more Kepler-138D transits to study its atmosphere.
These two possible water worlds Kepler-138c and D are not located in the habitable zone, and the temperature will allow liquid water to enter the surface of the rocky planet. But in data from Hubble and Spizzer , researchers also discovered the new planet Kepler-138e in the galaxy. The newly discovered planet is farther away from its star than the other three planets and takes 38 days to run.However, the nature of the additional planet remains undecided, as it does not seem to pass through its main star, and it will only allow astronomers to determine its size when passing through its main star.
researchers also had another surprise: they discovered that Kepler-138c and D are biplanets with nearly the same size and mass, which people thought were completely different before. On the other hand, the closer planet Kepler-138b has been proven to be an asteroid like the mass of Mars and is one of the smallest exoplanets known to date.
