... Scattered within this cavernous nebula, cataloged as NGC 604, are over 200 newly formed hot, massive, stars. At 1,500 light-years across, this expansive cloud of interstellar gas and dust is effectively a giant stellar nursery located some three million light-years distant in the spiral galaxy, M33. Hyakutake: Comet Atmosphere . ... The atmosphere of a comet comes and goes. ... Yesterday the Mars Global Surveyor project released a new close-up image of a portion of the Cydonia region on Mars. ...