... Dumbbell Nebula Close Up from Hubble . ... What causes unusual knots of gas and dust in planetary nebulas? ... Comet NEAT Approaches the Sun . ... A comet may likely become visible to the unaided eye over the next few days above the horizon where the Sun has just set. ... The Sun orbits the center of the Milky Way Galaxy. ... This enhanced Hubble Space Telescope image shows in remarkable detail the inner portion of the disk of dust and gas surrounding the star AB Aurigae. ...