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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 |
