Piaulet and associates observed exoplanets Kepler-138 c and Kepler-138 d with NASAs Hubble and the retired Spitzer space telescopes and discovered that the worlds could be composed mainly of water. To the left, the world Kepler-138 c, and in the background the planet Kepler 138 b, seen in silhouette transiting its main star. They are thought about a new class of “water planet,” unlike any significant world found in our solar system. Like the Earth, this exoplanet has an interior composed of metals and rocks (brown portion), but Kepler-138 d also has a thick layer of high-pressure water in different kinds: supercritical and possibly liquid water deep inside the world and a prolonged water vapor envelope (tones of blue) above it. Researchers warn the planets might not have oceans like those on Earth straight at the worlds surface area.
This is an artists illustration showing a cross-section of the Earth (left) and the exoplanet Kepler-138 d (right). Credit: Benoit Gougeon (University of Montreal).
NASAs Hubble and Spitzer Find Two Exoplanets May Be Mostly Water.
In the 1995 post-apocalyptic action film “Waterworld” Earths polar ice caps have entirely melted, and the water level has increased to over 5 miles, covering almost all of the land. Astronomers have actually revealed a set of worlds that are real “water worlds,” unlike any planet found in our solar system.
And yet, they are denser than the gas-giant outer worlds orbiting our Sun. The best answer is that these exoplanets have global oceans at least 500 times deeper than the average depth of Earths oceans, which simply are a wet veneer on a rocky ball.
The planets were found in 2014 with NASAs Kepler Space Observatory. Follow-up observations with the Spitzer and Hubble area telescopes discovered that the worlds must be composed mainly of water.
Do not expect to discover fish in the global oceans. They are most likely too warm and under very high pressure, therefore theres no such thing as a discrete limit in between the ocean surface area and planet environment.
Using data from NASAs Hubble and Spitzer Space Telescopes, astronomers found proof that 2 exoplanets orbiting a star 218 light-years away are “water worlds,” where water comprises a big fraction of the whole world. Credit: NASA Goddard Space Flight Center, Lead Producer: Paul Morris.
2 Exoplanets May Be Mostly Water, NASAs Hubble and Spitzer Find.
The telescopes cant directly observe the worlds surfaces, their densities suggest theyre lighter than rock worlds but heavier than gas-dominated ones.
A group led by researchers at the University of Montreal has found evidence that two exoplanets orbiting a red dwarf star are “water worlds,” where water makes up a large portion of the whole world. These worlds, located in a planetary system 218 light-years away in the constellation Lyra, differ from any planet discovered in our solar system.
The team, led by Caroline Piaulet of the Trottier Institute for Research on Exoplanets (iREx) at the University of Montreal, released an in-depth study of this planetary system, called Kepler-138, in the journal Nature Astronomy on December 15.
Piaulet and associates observed exoplanets Kepler-138 c and Kepler-138 d with NASAs Hubble and the retired Spitzer space telescopes and discovered that the planets might be composed mainly of water. These 2 planets and a smaller planetary buddy better to the star, Kepler-138 b, had actually been found previously by NASAs Kepler Space Telescope. The new research study discovered evidence for a fourth world, too.
In this illustration super-Earth Kepler-138 d remains in the foreground. To the left, the world Kepler-138 c, and in the background the planet Kepler 138 b, seen in shape transiting its main star. Kepler 138 is a red dwarf star located 218 light-years away. The low density of Kepler-138 c and Kepler-138 d– which are almost similar in size– indicates that they must be composed largely of water. They are both twice Earths mass however have approximately half of Earths density, and for that reason can not be solid rock. This is based on measurements of their mass versus physical size. They are considered a new class of “water planet,” unlike any significant planet discovered in our planetary system. Kepler-138 b is one of the smallest exoplanets understood, having the mass of the world Mars and the density of rock. Credit: NASA, ESA, Leah Hustak (STScI).
Water wasnt directly discovered at Kepler-138 c and d, however by comparing the sizes and masses of the planets to designs, astronomers conclude that a significant fraction of their volume– up to half of it– need to be made from materials that are lighter than rock but much heavier than hydrogen or helium (which make up the bulk of gas giant worlds like Jupiter). The most typical of these prospect materials is water.
” We previously believed that planets that were a bit bigger than Earth were big balls of metal and rock, like scaled-up variations of Earth, whichs why we called them super-Earths,” discussed Björn Benneke, study co-author and professor of astrophysics at the University of Montreal. “However, we have actually now shown that these 2 planets, Kepler-138 c and d, are rather different in nature and that a big portion of their entire volume is most likely composed of water. It is the best evidence yet for water worlds, a type of planet that was thought by astronomers to exist for a long period of time.”.
With volumes more than 3 times that of Earth and masses twice as huge, planets c and d have much lower densities than Earth. Due to the fact that many of the planets just slightly larger than Earth that have actually been studied in information so far all seemed to be rocky worlds like ours, this is surprising. The closest comparison, state researchers, would be a few of the icy moons in the external solar system that are likewise largely made up of water surrounding a rocky core.
” Imagine bigger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star,” described Piaulet. “Instead of an icy surface area, they would harbor large water-vapor envelopes.”.
Like the Earth, this exoplanet has an interior composed of rocks and metals (brown portion), however Kepler-138 d also has a thick layer of high-pressure water in different types: possibly liquid and supercritical water deep inside the world and a prolonged water vapor envelope (tones of blue) above it. The Earth, in contrast, has a negligible portion of liquid water with a typical ocean depth of less than 2.5 miles (4 kilometers).
Scientists caution the worlds may not have oceans like those in the world directly at the worlds surface. “The temperature in Kepler-138 ds atmosphere is likely above the boiling point of water, and we expect a thick dense environment made from steam on this planet. Only under that steam atmosphere there could potentially be liquid water at high pressure, and even water in another stage that happens at high pressures, called a supercritical fluid,” Piaulet said.
In 2014, data from NASAs Kepler Space Telescope allowed astronomers to announce the detection of 3 planets orbiting Kepler-138. This was based on a quantifiable dip in starlight as the world temporarily passed in front of their star.
Benneke and his colleague Diana Dragomir, from the University of New Mexico, created the concept of re-observing the planetary system with the Hubble and Spitzer area telescopes between 2014 and 2016 to capture more transits of Kepler-138 d, the 3rd planet in the system, in order to study its atmosphere.
A new exoplanet in the system.
The 2 possible water worlds, Kepler-138 c and d, are not situated in the habitable zone, the location around a star where temperatures would allow liquid water on the surface area of a rocky planet. In the Hubble and Spitzer data, scientists additionally discovered proof for a new planet in the system, Kepler-138 e, in the habitable zone.
This recently found planet is little and farther from its star than the 3 others, taking 38 days to finish an orbit. The nature of this extra planet, nevertheless, remains an open question since it does not appear to transit its host star. Observing the exoplanets transit would have permitted astronomers to identify its size.
With Kepler-138 e now in the picture, the masses of the previously known planets were measured once again via the transit timing-variation approach, which consists of tracking small variations in the exact minutes of the planets transits in front of their star triggered by the gravitational pull of other close-by planets.
The scientists had another surprise: they discovered that the 2 water worlds Kepler-138 c and d are “twin” planets, with practically the exact same size and mass, while they were previously believed to be dramatically various. The closer-in world, Kepler-138 b, on the other hand, is confirmed to be a small Mars-mass world, among the tiniest exoplanets known to date.
” As our methods and instruments end up being sensitive sufficient to discover and study planets that are further from their stars, we might start finding a lot more of these water worlds,” Benneke concluded.
Recommendation: “Evidence for the volatile-rich structure of a 1.5-Earth-radius planet” by Caroline Piaulet, Björn Benneke, Jose M. Almenara, Diana Dragomir, Heather A. Knutson, Daniel Thorngren, Merrin S. Peterson, Ian J. M. Crossfield, Eliza M.-R. Kempton, Daria Kubyshkina, Andrew W. Howard, Ruth Angus, Howard Isaacson, Lauren M. Weiss, Charles A. Beichman, Jonathan J. Fortney, Luca Fossati, Helmut Lammer, P. R. McCullough, Caroline V. Morley and Ian Wong, 15 December 2022, Nature Astronomy.DOI: 10.1038/ s41550-022-01835-4.
The Hubble Space Telescope is a job of worldwide cooperation in between NASA and ESA. NASAs Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope.
