Comet Encke was "discovered" in 1786, 1795,1805, and 1818 by different astronomers. These comets were found to be the same only after orbital calculations in 1819 by the German astronomer Johann Encke, who then predicted its return in 1822.

A new look at how light bends as it travels through the universe could point to an alternative theory of gravity

Retrograde motion is an effect of changing perspective. Inferior planets Mercury and Venus show retrograde motion on either side of inferior conjunction. They "overtake" Earth as they pass between Earth and the Sun.

Supermassive black hole winds blowing at 36 million mph can sculpt entire galaxies

First discovered in 1826, the Bug Nebula is one of the brightest planetary nebulae. The central star is thought to have an extremely high temperature, and its intense heat lights up the surrounding stellar material.

Some scientists speculate that the universe is shaped like a doughnut, instead of stretching to infinity. It’s a topology that could eventually be mapped.