Supernova remnant is an unusual suspect

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 10 June, 2009

An unusually shaped supernova remnant observed in the Small Magellanic Cloud is likely the remains of an exploded white dwarf.

The new image, taken by NASA’s Chandra X-ray Observatory, shows SNR 0104-72.3 (SNR 0104 for short), in the Milky Way’s neighbouring galaxy the Small Magellanic Cloud. Astronomers think that SNR 0104 is the remains of a so-called Type Ia supernova caused by the thermonuclear explosion of a white dwarf.

In this composite made of X-rays from Chandra shown in purple and infrared data from Spitzer shown in green and red, SNR 0104 looks unlike other likely Type Ia remnants found in our own Galaxy. Image: X-ray (NASA/CXC/Penn State/S.Park & J.Lee); IR (NASA/JPL-Caltech).

White dwarfs are the final evolutionary state of most stars, the dense core left behind after a red giant has shed its outer layers. One possible explanation of the curious structure is that the explosion of the white dwarf itself was strongly asymmetrical and produced two bright lobes of emission, seen to the upper right and lower left in the image. The large amount of iron in these lobes indicates that SNR 0104 was likely formed by a Type Ia supernova.

The explosion may also have been influenced by a complicated surrounding environment. The green shells on the left and right side of the remnant correspond to local material that has been swept up by the explosion. Therefore, the lack of material to the north and south of the star may have biased the direction in which the stellar debris expanded.

The explosion mechanism, and the possible effect of the environment will provide the focus for future study by astronomers working on the supernova.

SNR 0104 may also provide key information about the little studied class of so-called “prompt” Type Ia supernovas caused by the demise of younger, more massive stars than average. Astronomers speculate that SNR 0104 might be located within a star-forming region, and note the presence of a nearby massive star. Again, more data will be needed to test this hypothesis.

The new image was released during the 214th meeting of the American Astronomical Society held in Pasadena, California, this week.

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