Two planets that astronomers discovered on the Kepler mission may not be the rocky, Earth-like bodies we originally believed. Instead, a new study suggests they could be two aquatic worlds, and that they are less dense than astronomers originally postulated.
What is intriguing about these worlds is that they are thought to be somewhat similar to Europa, which is a rocky core encased in water and covered in ice. However, these two worlds are closer to their star than Europa and its planet. As such, scientists believe that the surface of the planets probably blurs between liquid water and steam.
When we first discovered these water worlds in the Kepler system, there was nothing especially intriguing about them to warrant a second look. However, astronomers believed that it would be a good candidate for investigating the atmospheres of exoplanets within the system. As such, new studies began on the planets we discovered there.
To dig deeper, the researchers began looking at data from the system captured by the Hubble and Spitzer Space Telescopes. Because the planets are so close, they create what astronomers call «transit time variances,» meaning the planet doesn’t appear in front of its host exactly when the orbit would normally take it there.
This means that any data collected by observing the transit of the planets in a system will be out of sync in some way. However, by looking at data collected with the Hubble and Spitzer Space Telescopes after the discovery of the water worlds, the researchers were able to create a timeline based on a span of seven years. This provided more details about the worlds found on Kepler.
The researchers then discovered that the data they collected from the Kepler mission did not allow for correct transit times. Instead, they had to slightly change the equation to a four-planet model instead of the three-planet model they were using before. When they were done, they found that the transit times made the most sense.
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It was this change in the model that forced astronomers to reevaluate how they viewed the two worlds they believed to be rocky and dense. With a four planet model, it made more sense for the planets to be less dense, perhaps even water worlds. That’s because the planets are very close together, which means that the gravitational pull of each affects the others.
But, this fourth world has not yet been seen transiting in front of the star within the Kepler system. As such, the watery worlds aren’t the only mystery keeping astronomers looking toward this star system. When we find out, if we can learn more about it, perhaps it could provide even more evidence of these aquatic worlds. Or, it could turn everything we know on its head.
