Astronomy Picture of the Day . Mercury on the Horizon . ... Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it is never seen far from the Sun, and so is only visible near sunrise or sunset. If trailing the Sun, Mercury will be visible for several minutes before it follows the Sun behind the Earth. ... In the above picture, astronaut John W. A Wind From The Sun . ... Weak Lensing Distorts the Universe . ... Supernova 1994D and the Unexpected Universe . ...