Still a lot of those light gases around – when the solar system was young. Primarily composed of hydrogen and helium, it must have formed while there was Of the light gases that remain in the original nebula. After the firstįew million years in the star’s life, a wind is generated that blows away most Same light gases that the Sun is made of – hydrogen and helium. Relatively soon after the birth of the Sun, because it is mostly made of the Jupiter was likely the first of the planets, forming We’ve observed half-formed stars – disks of gas in the midst ofĬollapsing – and Jupiter-like planets orbiting other stars. Seem that whatever process produced our solar system is at work across the It isn’t clear what triggered this collapse, but it does Of the swirling cloud would condense to form Earth and the other planets,Īsteroids and comets. Hydrogen gas, most of the nebula became the star we know as the Sun. "Only under that steam atmosphere there could potentially be liquid water at high pressure, or even water in another phase that occurs at high pressures, called a supercritical fluid.Four and a half billion years ago, a giant cloud of gas andĭust, called a nebula, collapsed to form our solar system. "The temperature in Kepler-138 d's atmosphere is likely above the boiling point of water, and we expect a thick dense atmosphere made of steam on this planet, Ms Piaulet said. That's because the two possible water worlds are not located in the habitable zone, the area around a star where temperatures would allow liquid water on the surface of a rocky planet. It would be all but impossible for humans to even reach these exoplanets due to their distance from us.Īnd even if were we were able to travel to them, their oceans might not be anything like the ones we're used to. "Instead of an icy surface, they would harbour large water vapour envelopes." Could humans survive on Kepler-138 c and d? "Imagine larger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star," explained study lead Caroline Piaulet. The closest comparison, say researchers, would be some of the icy moons in the outer Solar System that are also largely composed of water surrounding a rocky core.
Researchers were surprised at this discovery because most of the planets slightly bigger than Earth that have been studied in detail so far all seem to be rocky worlds like ours.
"It is the best evidence yet for water worlds, a type of planet that was theorised by astronomers to exist for a long time."ĭespite being three times the volume and twice the mass as Earth, Kepler-138 c and d have much lower densities than Earth.
"However, we have now shown that these two planets, Kepler-138 c and d, are quite different in nature and that a big fraction of their entire volume is likely composed of water. "We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that's why we called them super-Earths," explained Björn Benneke, professor of astrophysics at the University of Montreal. The discovery of these two possible "water worlds" could change that. While frozen water has been observed on multiple moons in our outer Solar System, scientists have so far been unsuccessful in finding planets with their own versions of Earth's lush oceans. Photo: Supplied / NASA / Benoit Gougeon, University of Montreal Why is this discovery important? Measurements of Kepler-138d’s density suggest it could have a water layer that makes up more than 50% of its volume. This illustration shows cross-sections of the Earth and the exoplanet Kepler-138d. What is an exoplanet?Īn exoplanet is any planet that orbits a star outside our solar system.Ĭonsidering Kepler-138 c and Kepler-138 d are 218 light-years away in the constellation Lyra, they are definitely in the exoplanet category. The most common of these candidate materials is water. While water hasn't been directly detected on either exoplanet, by comparing their sizes and masses to models, astronomers concluded that a significant fraction of their volumes - up to half - should be made of materials lighter than rock but heavier than hydrogen or helium. Photo: Supplied / NASA, ESA, Leah Hustak (STScI)Īstronomers using NASA's Hubble and Spitzer telescopes have made a discovery which has brought them a micro-step closer to confirming that planets beyond our own might harbour Earth-like oceans.Ī team of University of Montreal researchers discovered two exoplanets, Kepler-138 c and Kepler-138 d, that they believe are largely made up of water.
In this illustration, exoplanet Kepler-138 d is in the foreground and Kepler-138 c is on the left.
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