Figure 1
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| Figure 2 | Figure 3 | Figure 4 | Figure 5 |
This image composite compares the well-known visible-light picture of
the glowing Trifid Nebula (left panel) with infrared views from NASA's
Spitzer Space Telescope (remaining three panels). The Trifid Nebula
is a giant star-forming cloud of gas and dust located 5,400 light-years
away in the constellation Sagittarius.
The false-color Spitzer images reveal a different side of the Trifid
Nebula. Where dark lanes of dust are visible trisecting the nebula in the
visible-light picture, bright regions of star-forming activity are seen
in the Spitzer pictures. All together, Spitzer uncovered 30 massive
embryonic stars and 120 smaller newborn stars throughout the Trifid
Nebula, in both its dark lanes and luminous clouds. These stars are
visible in all the Spitzer images, mainly as yellow or red spots.
Embryonic stars are developing stars about to burst into existence. Ten
of the 30 massive embryos discovered by Spitzer were found in four dark
cores, or stellar "incubators," where stars are born. Astronomers using
data from the Institute of Radioastronomy millimeter telescope in Spain
had previously identified these cores but thought they were not quite
ripe for stars. Spitzer's highly sensitive infrared eyes were able to
penetrate all four cores to reveal rapidly growing embryos.
Astronomers can actually count the individual embryos tucked inside the
cores by looking closely at the Spitzer image taken by its infrared array
camera (figure 4). This instrument has the highest spatial resolution of
Spitzer's imaging cameras. The Spitzer image from the multiband imaging
photometer (figure 5), on the other hand, specializes in detecting
cooler materials. Its view highlights the relatively cool core material
falling onto the Trifid's growing embryos. The middle panel is a
combination of Spitzer data from both of these instruments.
The embryos are thought to have been triggered by a massive "type O" star,
which can be seen as a white spot at the center of the nebula in all four
images. Type O stars are the most massive stars, ending their brief lives
in explosive supernovas. The small newborn stars probably arose at the
same time as the O star, and from the same original cloud of gas and dust.
The Spitzer infrared array camera image is a three-color composite of
invisible light, showing emissions from wavelengths of 3.6 microns (blue),
4.5 microns (green), 5.8 and 8.0 microns (red). The Spitzer multiband
imaging photometer image (figure 3) shows 24-micron emissions. The Spitzer mosaic
image combines data from these pictures, showing light of 4.5 microns
(blue), 8.0 microns (green) and 24 microns (red). The visible-light image
(figure 2) is from the National Optical Astronomy Observatory, Tucson, Ariz.
