[alexander_busek]

That close together, two planets would not survive each other’s tidal forces (the Roche limit). It’s a common oversight by artists. But I’ll just assume someone is using a telephoto lens instead.

It's a common oversight by laymen to forget that the Roche Limit applies only to satellites which are held together only by their own gravity - i.e., which are not held together by forces other than gravity and which are thus essentially fluid.

Jupiter's Metis and Saturn's Pan are within the Roche Limit, as are countless artificial satellites in Earth orbit.

Their tensile strength allows them to resist disintegration.

Regards,

[Telepathic Intruder]

Yes, of course. And by the way, that doesn't rule out a planet (or moon) having something big in their skies, it just rules out having something big and close, because tidal forces decrease far more rapidly with distance than total gravitational force (an inverse cube law instead of an inverse square). So it's perfectly reasonable for Pandora in the Avatar movie to have a looming gas giant in the sky, but not a close-orbiting similar-massed object.