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).
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