Can you imagine what Earth would be like if its axis wobbled about during your lifetime? The axis’ steady tilt in one direction causes the amount of sunlight each hemisphere receives to vary in a predicable way, giving us the familiar four seasons.
Enter Kepler-413b, a giant gas planet located 2,300 light years away in the constellation Cygnus the Swan. Its axis is tiled 30 degrees from vertical and wobbles like a top over a remarkably short period of just 11 years. Seasons would change erratically and rapidly, so much you’d hardly know what to wear month to month.
Earth’s axis wobbles too but so slowly we don’t notice it at all during our lifetime. It’s called precession and amounts to 23.5 degrees over 26,000 years.
Keep in mind that the axis doesn’t flip-flop around – it maintains a tilt of 23.5 degrees just like Kepler 423-b keeps its axis tipped at 30 degrees. Instead, the axis describes a repeating circle in the sky as the planet wobbles.
Another view of Earth’s precession or wobble
Kepler 423-b’s orbit around the dwarf star pair appears to wobble, too, because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the star pair’s orbit. As seen from Earth, the wobbling orbit moves up and down continuously.
The Kepler telescope, when it was still active, discovered planets by watching a star’s light repeatedly dim when a planet transited across its face one orbit after another. But something unexpected happened with Kepler 413b. The transits disappeared for a while and then returned, implying a weirdly oscillating orbit.
“Looking at the Kepler data over the course of 1,500 days, we saw three transits in the first 180 days — one transit every 66 days — then we had 800 days with no transits at all. After that, we saw five more transits in a row,” said Veselin Kostov, the principal investigator on the observation.
No one’s sure yet what causing the orbit to continuously change its tilt.
It’s possible Kepler 413-b feels the tug of yet-to-be-discovered planets in nearby orbits. A neighboring third star may be gravitationally bound to the stellar pair and exert an influence too.
Kepler 413-b, even if it has seasons, is probably too darn hot for life anyway. It orbits so close its parent suns liquid water’s not an option. So I guess no one will ever have to switch from shorts on Sunday to snow pants on Monday there.