While NASA is still analyzing the proposals for a new use of the Kepler space telescope after the end of its mission, scientists are still examining the data collected in the past years. The observations of the binary system Kepler-413 have allowed them to discover an exoplanet called Kepler-413b that’s really pecutliar, especially because its axis wobbles like a spinning top, causing violent changes in its seasons.
The Kepler-413 system consists of two small stars, an orange dwarf and a red dwarf about 2,300 light-years away from Earth. They’re very close to each other so the planet Kepler-413b orbits both of them in about 66 Earth days. It’s considered a super-Neptune because it’s a gas giant with a mass about 65 times that of Earth.
It’s normal for the axis of a planet to have a certain oscillation, a phenomenon called precession, but Kepler-413b seems really a child’s top. For a comparison, the Earth’s axis has a 23.5 degrees tilt over the course of 26,000 years while that of Kepler-413b may vary up to 30 degrees over the course of just 11 years.
This oscillation causes violent season changes that are extremely rapid and irregular because they are determined exactly by the tilting of a planet axis. Its surface is in all cases too hot to host liquid water and therefore life forms of a known type. That’s because the planet is very close to its stars, a little closer than the distance of Mercury from the Sun, and even if they’re small it’s still receiving a lot of heat.
The orbit of the planet Kepler-413b wobbles as well because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the two stars’ orbit. Generally, the observations of a planet are regular but because of its unusual orbit, over a period of 1500 days of observations by the Kepler space telescope three transits in front of its stars have been observed in 180 days, then a transit every 66 days but then there were 800 days with no transits. After this long break there were five more transits.
The orbit of the planet Kepler-413b may wobble due to other celestial bodies that haven’t yet been identified. There may be other planets with strange orbits, or even a third star that have a gravitational influence on Kepler-413b. The next transit of this planet is predicted to take place only in 2020.
Multiple stellar systems often offer surprises because the gravitational dynamics are complex. The Kepler-413 system confirms it but there could be many more planets like that or even stranger, however we can’t see them because of unfavorable positions or for other reasons. Astronomers keep on looking for them, confident that they will find other planets at least as strange.
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