"Window-Curtain" Structure of the Orion Nebula
Recent images made with the Wide Field/Planetary Camera on NASA's Hubble Space Telescope have revealed the structure of a thin sheet of gas located at the edge of the famous "Great Nebula" in Orion, an estimated 1500 light years from Earth.
Astronomers, who compare the appearance of this sheet of gas with that of a rippled window curtain, report that this emission traces the boundary between the hot, diffuse interior of the nebula and an adjacent dense cool cloud. The sheet is seen in light emitted by atoms of gaseous sulfur (shown in red in the photograph). This emission is strongest under conditions which are intermediate between those in the interior of nebula and those in the dense cloud. The sulfur emission is seen to break into filamentary and clumpy structures with sizes down to the limit of what the telescope can show. In contrast, emission from gaseous oxygen and hydrogen (shown as blue and green, respectively) is favored in the interior of the nebula itself, and is distributed much more smoothly in the image.
The Orion Nebula is a "stellar nursery" - a region where new stars are forming out of interstellar gas. The emission from the nebula is powered by the intense ultraviolet light from a cluster of particularly hot and luminous stars. The sulfur emission seen in the photograph is coming from the region where the light from these stars is "boiling off" material from the face of the dense cloud. This is the very cloud from which the hot stars formed, and is known to harbor additional ongoing star formation.
Astronomers say that this is a good example of a case where, despite the spherical aberration that has hobbled many of the scientific programs which the Hubble Space Telescope was expected to carry out, the telescope can still be used to obtain scientifically interesting data with clarity far exceeding that normally possible from the ground.
The Wide Field/Planetary Camera was designed and built by the Jet Propulsion Laboratory, which is operated by the California Institute of Technology.