What would the sky look like if Earth orbited a brown dwarf?

Answer 1

An Earth orbiting a brown dwarf in the habitable zone would be tidally locked to the star. So, on the side of the Earth permanently facing away from the brown dwarf the sky would be black, with only the stars or other planets shining down.

For the other side of the planet, the one permanently facing the star:-

If it orbited one of the younger and hotter brown dwarfs, late M-spectral

class to early L-spectral

class, the Earth's sky would probably appear white with reddish-pink

clouds and the brown dwarf star would look much like the Sun, dazzling white, but a lot bigger.

The cooler the Brown dwarf star gets, the bigger and yellowier,

orangier

and then redder the star would appear in the sky. The sky and clouds would also become redder and darker until the clouds and then the sky are dark.Cooler thanaround the mid L-spectral

class,sodium and potassiumin the star's atmospherecouldgive the star a faint reddish-purple

hue because these elements are absorbing most of the star's emitted green light leaving a mixture of blue and red light. By mid T-spectral

class the star is giving off such a small proportion of blue light that the brown dwarf loses its magenta hue and appears redwith the sky behind it now almost black.

The heat on an inhabitable Earth orbiting around the coldest brown dwarfs would come from inside the planet itself, perhaps generated by tidal interaction with the star but almost no heat coming from the star's light. Therefore the sky from an Earth around the coldest brown dwarf would be much like the sky as seen from a rogue planet wandering through space by itself, without a sun.

With the very coldest brown dwarfs, Y-spectral

class, even the brown dwarf star itself would be invisible in the Earth's sky. It would be nothing but a big black disc obscuring some of the stars in an otherwise black sky.

Answer 2

If Earth orbited a brown dwarf, the sky would appear a reddish color due to the dim light emitted by the brown dwarf. The Sun would be much larger in the sky compared to a regular star, appearing as a bright disk. Daytime would be significantly darker due to the reduced light output of the brown dwarf.