Planet of the Day: Kepler 413b

This planet is a wild one. The planet has been found to precess  around 30 degrees in less than 11 years. Some of you may wonder what precession is. Well, basically it is the wobble of an object as it rotates. It happens to tops, and it does indeed happen on planet Earth too. There are various forms of precessions. The planet’s angle of rotation could change, which Kepler 413b does extremely quickly, and like the top, the axis of rotation itself could rotate in a circle. The planet Earth though, precesses so slowly that you need to wait thousands of years so you can even begin to see the change of the positions of the stars. Not in the case of this planet, wobbling without any stability.

There are also the orbital kind of precessions. Before going further, you should be aware that all orbits are ellipses, with the center of mass at a focus. Meaning, the orbits are not perfect circles, more like ovals, and the center of mass is not in the perfect center of the oval, but offset by a specific mathematical amount to a place called the focus. This means that in the case of orbital precession, the shape of the oval rotates around the focus itself over a large period of time. Mercury is famous for having a large orbital precession, caused by a combination of the gravitational pull of other Solar System objects and the mechanics of general relativity (aka the most accurate theory of gravity yet) itself.

The case of this planet is odd, though. When they first detected the planet by observing that the brightness of the star fell, signifying that the planet went in front of the star. They observed further cycles of the planet moving in front of the star. At one point, though, no object blocked the star’s light. And it kept going like this for many days until once again, they detected the same planet blocking the star’s light again and again. The significance of this discovery is compelling. It means the orbit is wobbling up and down, at times having the planet move in front of the star, at times above or below it.

The combination of all those factors would make seasonal changes of this planet extreme and unpredictable. As for what could have cause this? At this point, any theory about what happened would be speculation. We just don’t have enough data. The link itself gives plausible scenarios, though.

As for the physical characteristic itself, it is a gas giant. It is really close to its parent star, making its temperature very hot. It is 65 times the mass of the Earth, making it many times more massive than Neptune, but less massive than Saturn. While this goes in line with other gas giant discoveries, that its behavior deviates so much from what we have seen other planets do in their spin and orbit makes it a noteworthy object of study.


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