Because planets might accumulate a significant fraction of their mass and angular momentum from only a few large impacts, stochastic effects may be important in determining spin obliquities 1.

The other widely used technique for measuring stellar obliquities, the Rossiter–McLaughlin effect 9, relies on precise spectroscopy during transits and would be impractical for a star as faint ...

For the Earth, this tilt or “obliquity” is 23° and is responsible for the changing seasons. Scientists now know that the obliquities of the smaller planets, Mercury, Mars and Venus, change over time.

Scientists suspect, however, that exoplanets may exhibit a host of obliquities, resembling anything from a vertical spinning top to a horizontal rotisserie. The more extreme the tilt, the less ...