PHOTO NO.: STScI-PRC96-38b


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.  Other hot stars, also present in the nebula, are ionizing the
extended optical nebulosity.  The ionizing radiation induces photo-evaporation
of the surfaces of the clouds and drives away violent stellar winds tearing
into the cool clouds.

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.

The Lagoon Nebula and nebulae in other galaxies are sites where new stars are
being born from dusty molecular clouds.  These regions are the "space
laboratories" for the astronomers to study how stars form and the interactions
between the winds from stars and the gas nearby.  By studying the wealth of
data revealed by HST, astronomers will understand better how stars form in the
nebulae.

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).

This work is based on public data retrieved from the HST Archive, cosmic-ray
cleaned, calibrated and combined by Adeline Caulet (Space Telescope European
Coordinating Facility, European Space Agency). 

Credit: A. Caulet (ST-ECF, ESA) and NASA