Left
image: The X-ray data from the Chandra X-ray Observatory have revealed a bright
central star surrounded by a cloud of multimillion-degree gas in the planetary
nebula known as the Cat’s Eye. This Chandra image, where the intensity of the
X-ray emission is correlated to the brightness of the orange coloring, captures
the expulsion of material from a star that is expected to collapse into a white
dwarf in a few million years. The intensity of X rays from the central star was
unexpected, and it is the first time astronomers have seen such X-ray emission
from the central star of a planetary nebula. The ACIS X-ray camera aboard
Chandra observed NGC 6543 on May 10-11, 1999, for a total exposure time of
46,000 seconds.
Right image: This composite image of Chandra and Hubble Space Telescope data
offers astronomers an opportunity to compare where the hotter, X-ray emitting
gas appears in relation to the cooler material seen in optical wavelengths. The
Chandra team found that the chemical abundances in the region of hot gas (its
X-ray intensity is shown in purple) were like those in the wind from the central
star and different from the outer cooler material (the red and green
structures.) Although still incredibly energetic and hot enough to radiate X
rays, Chandra shows the hot gas to be somewhat cooler than scientists would have
expected for such a system. These results present a puzzle since the temperature
of the X-ray emitting material suggests that mixing might have occurred. This
discrepancy means some other process has created the "lukewarm" X-ray
emission observed by Chandra. The color composite of optical and X-ray images
was made by Zoltan G. Levay (Space Telescope Science Institute). The optical
images were taken by J.P. Harrington and K.J. Borkowski (University of Maryland)
with the Hubble Space Telescope.
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