Thin atmosphere is enough to keep many exoplanets spinning

The majority of stars in our galaxy, and most likely the Universe as a whole, are small, (relatively) dim, low mass bodies. Because they emit much less light, the habitable zone for these stars is close in, where planets would take weeks to complete a full orbit. That's also close enough where the star's gravity can create tidal interactions with the planet's interior, slowing its spin until the planet perpetually shows a single face to the star (much like our Moon does to Earth).

Needless to say, leaving one side of the planet perpetually in the dark could have some rather interesting effects on the environment, including the idea of an "eyeball Earth." That's where the area facing the host star is melted while the rest of the planet remains a frozen wasteland. But now some researchers have suggested eyeball Earths may be a rarity: an atmosphere like Earth's is enough to keep a body from becoming tidally locked.