* Astronomy

It may look as if it was taken by the orbiting Hubble Space Telescope, but this new image of the famous Trifid Nebula was snapped from Earth.
The terrific Trifid pictures were captured by astronomers at the European Southern Observatory, using an instrument called the Wide-Field Imager camera attached to the 2m Max-Planck-ESO telescope located at the ESO's facility in La Silla, Chile.
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This image composite combines the well-known visible-light picture of the glowing Trifid Nebula with infrared views from NASA's Spitzer Space Telescope. The Trifid Nebula is a giant star-forming cloud of gas and dust located 5,400 light-years away in the constellation Sagittarius.


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Position (2000): RA: 18h02m23.40s Dec: -23d01m50.10s
This image of the Trifid Nebula combines data from two of Spitzer's instruments.
The Spitzer infrared array camera image is a three-colour 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 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 is from the National Optical Astronomy Observatory, Tucson, Arizona.
Credit: NASA/JPL-Caltech

The false-colour Spitzer image 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 millimetre 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. This instrument has the highest spatial resolution of Spitzer's imaging cameras. The Spitzer image from the multiband imaging photometer, on the other hand, specialises in detecting cooler materials. Its view highlights the relatively cool core material falling onto the Trifid's growing embryos.

The embryos are thought to have been triggered by a massive "type O" star, which can be seen as a white spot at the centre 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.