apr 052014


April 5, 2014

The Dragonfish Nebula, an emission nebula in the Crux


Image Credit: NASA/JPL-Caltech/Univ. of Toronto

The Dragonfish Nebula, named for its resemblance to a terrifyingly toothy deep-sea fish on infrared images, is an emission nebula and star-forming region of about of 450 light-years across, located some 30,000 light-years away from Earth in the southern constellation of the Crux (but better known for the name of its cross-shaped asterism: the Southern Cross).

Due to the distance and location of this massive nebula, there’s a vast amount of interstellar material (such as gas and dust) between us and the Dragonfish, absorbing its light, so in optical light it’s essentially invisible. But infrared light can pierce that fog, and the image above was taken using NASA’s Spitzer Space Telescope, designed to look in the infrared.

In 2010 the first hint of a star cluster was found in the form of a big cloud of ionized gas (the Dragonfish Nebula). Its microwave emissions led to the suspicion that radiation from massive stars nearby had ionized the gas. A little later a knot of 400 massive stars in the cloud’s heart have been identified. The cluster probably contains many more stars too small and dim to see.

The surrounding cloud of ionized gas is producing more microwaves than clouds around other star clusters in our Milky Way galaxy. That suggests the Dragonfish contains the brightest and most massive young cluster discovered so far, with a total mass in the range of 100,000 times the mass of our Sun. Because it is located nearby in our own galaxy, it can be studied in great detail.

The strong stellar winds of the young and massive stars have blown a bubble in the gas and dust, carving out a shell of more than 100 light-years across (seen in the lower, central part of this image). This shell forms the “toothy mouth” of the Dragonfish, and the two bright spots make it up its beady eyes.

The infrared light in this region is coming from the gas and dust that are being heated up by the unseen central cluster of massive stars. The bright spots along the shell, including the “eyes,” are possible smaller regions of newly formed stars, triggered by the compression of the gas and dust by winds from the central, massive stars.

This infrared image was taken by NASA’s Spitzer Space Telescope. The infrared light was captured by the infrared array camera on Spitzer, at wavelengths of 3.6 microns (blue); 4.5 microns (green); and 8.0 microns (red). The data were captured before Spitzer ran out of its liquid coolant in 2009, and began its “warm” mission.

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