Giant Twisters in the Lagoon Nebula
This NASA Hubble Space Telescope (HST) image reveals a pair of one-half light-year long interstellar "twisters, " eerie funnels and twisted-rope structures in the heart of the Lagoon Nebula (Messier 8) which lies 5, 000 light-years away in the direction of the constellation Sagittarius. The central hot star, O Herschel 36 (lower right), is the primary source of the ionizing radiation for the brightest region in the nebula, called the Hourglass. Analogous to the spectacular phenomena of Earth tornadoes, the large difference in temperature between the hot surface and cold interior of the clouds, combined with the pressure of starlight, may produce strong horizontal shear to twist the clouds into their tornado-like appearance. Though the spiral shapes suggest the clouds are "twisting, " future observations will be needed, perhaps with Hubble's next generation instruments, with the spectroscopic capabilities of the Space Telescope Imaging Spectrograph (STIS) or the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), to actually measure velocities. These color-coded images are the combination of individual exposures taken in July and September, 1995 with Hubble's Wide Field and Planetary Camera 2 (WFPC2) through three narrow-band filters (red light ionized sulphur atoms, blue light, double ionized oxygen atoms, green light, ionized hydrogen).