Scientists may have found the first water worlds - Ars Technica

NASA, ESA, Leah Hustak

Two planets that were primitively discovered by the Kepler ngo whitethorn not beryllium what we thought they were. Based connected an archetypal characterization, it was thought these planets were rocky bodies a spot larger than Earth. But continued reflection has produced information that indicates the planets are overmuch little dense than we primitively thought. And the lone realistic mode to get the benignant of densities they present look to person is for a important magnitude of their measurement to beryllium occupied by h2o oregon a akin fluid.

We bash person bodies similar this successful our Solar System—most notably the satellite Europa, which has a rocky halfway surrounded by a watery ammunition capped by ice. But these caller planets are overmuch person to their big star, which means their surfaces are astir apt a blurry bound betwixt a immense water and a steam-filled atmosphere.

Let’s revisit that

There are 2 main methods for uncovering an exoplanet. One is to ticker for dips successful the airy from their star, caused by planets with an orbit that takes them betwixt the prima and Earth. The 2nd is to way whether the star's airy periodically shifts to redder oregon bluer wavelengths, caused by the prima moving owed to the gravitational propulsion of orbiting planets.

Either of those methods tin archer america whether oregon not a satellite is present. But having some gives america a batch of accusation astir the planet. The magnitude of airy blocked by the satellite tin springiness america an estimation of its size. The magnitude of red- and blue-shifting of the star's airy tin bespeak the planet's mass. With some of those, we tin find retired its density. And density limits what sorts of materials it tin beryllium composed of—low density means affluent successful gas, precocious density means rocky with a metal-rich core.

That's precisely what we were capable to bash astatine the Kepler-138 system. Data from some these methods suggested that the strategy contains 3 planets. Kepler-138b appears to beryllium a small, Mars-sized rocky body. Kepler-138c and Kepler-138d some fell into the class of super-Earths: rocky planets that were somewhat larger than Earth and considerably much massive. All of them orbited rather adjacent to Kepler-138a, a reddish dwarf star, with the astir distant (Kepler-138d) orbiting astatine 0.15 astronomical units (the emblematic region betwixt Earth and the Sun).

In the expansive strategy of things, determination was thing antithetic astir this strategy that would request a 2nd look. But researchers thought that it made a bully campaigner for studies of the planet's atmospheres. While the satellite volition artifact each airy arsenic it transits successful beforehand of its big star, a tiny magnitude of airy volition walk done the ambiance connected its mode to Earth. And the molecules successful that ambiance volition sorb immoderate circumstantial wavelengths, allowing america to discern their presence.

To execute that study, a squad of researchers obtained information from the Hubble and Spitzer abstraction telescopes, timed for erstwhile Kepler-138d was transiting successful beforehand of the star. And that's erstwhile things started to get weird.