Various unknown astronomical objects have been hypothesized throughout recorded history. For example, in the 5th century BCE, the philosopher Philolaus defined a hypothetical astronomical object which
Artist's concept of Earth, orbited by a hypothetical second moon
Artist's concept of a carbon planet. The surface is dark and reddish from hydrocarbon deposits.
Blanet
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A blanet is an exoplanet that directly orbits a black hole.
Hypothetical astronomical object
…types of extrasolar planets include: Type Description Ammonia planet A planet with significant amounts of ammonia. May have lakes or oceans of ammonia. Blanet A planet that directly orbits a black hole. Carbon planet A terrestrial planet composed primarily of carbon, rather than silicon. Chthonian planet A…
Artist's impression of the view of the sky from a planet orbiting inside the dust disk around the supermassive black hole in the center of the galaxy NGC 4261
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