Wobbly Planet with Erratic Seasons Spotted by NASA's Kepler Space Telescope

Earth's unwavering 23.5 degree tilt on its axis is what gives us predictable seasons, but a planet spotted by NASA's Kepler space telescope wobbles on its axis like a spinning top, creating an environment with erratic seasonal changes.

This planet, designated as Kepler-413b, orbits a close pair of stars every 66 days, so temperatures there are too hot for life as we know it to exit, but over the course of observing it, astronomers have found that the tilt of the planet's spin axis can vary by as much as 30 degrees over 11 years, which causes rapid and erratic changes in seasons.

A scientific paper describing Kepler-413b's erratic orbit is published in The Astrophysical Journal.

Earth, by comparison, has not had a change in the tilt of its spin axis in 26,000 years, NASA said, noting that astronomers are amazed that Kepler-413b wobbles, or precesses, on a time scale observable in a human lifetime.

Kepler-413b's peculiar wobble was noticed by astronomers observing its transits, or number of times it passes in front of its host stars. A planet's transit is typically like clockwork, but astronomers observed an anomaly.

"What we see in the Kepler data over 1,500 days is three transits in the first 180 days (one transit every 66 days), then we had 800 days with no transits at all," explained Veselin Kostov, the principal investigator on the observation. "After that, we saw five more transits in a row."

Because of this orbital wobble, the planet's orbit continuously moves up or down relative to our view, and the change is large enough that from our vantage point on Earth the transit cannot be seen.

It just so happens that the planet was spotted in transit when it was viewable from Earth. The next transit of Kepler-413b is not expected until 2020.

"Presumably there are planets out there like this one that we're not seeing because we're in the unfavorable period," said Peter McCullough, a team member from the Space Telescope Science Institute and Johns Hopkins University . "And that's one of the things that Veselin is researching: Is there a silent majority of things that we're not seeing?"