Long-Sought Remnants of Massive Stars Found

A new class of cosmic object ? dubbed a ?super planetary nebula? ? has been identified by astronomers.

Planetary nebulas are shells of gas and dust expelled by stars near the end of their lives and are typically seen around stars comparable or smaller in size than the sun. These nebulas aren't related to planets ? the name arose because they resembled giant planets when viewed through early telescopes.

A team of scientists in Australia and the United States identified the new objects when they surveyed the Magellanic Clouds, the two companion galaxies to the Milky Way, with radio telescopes of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia Telescope National Facility.

They noticed that 15 radio objects in the Magellanic Clouds match with well known planetary nebulas observed by optical telescopes. The members of the new class of objects are unusually strong radio sources.

Whereas the existing population of planetary nebulas is found around small stars comparable in size to our sun, the new population may be the long predicted class of similar shells around heavier stars.

The team thinks that the detections of these new objects may help to solve the so called ?missing mass problem? ? the absence of planetary nebulas around central stars that were originally one to eight times the mass of the sun.

The nebular material around each star may have as much as 2.6 times the mass of the sun, whereas the material around smaller stars weighs in around only 0.3 times the mass of the sun.

"This came as a shock to us," said Miroslav Filipovic of the University of Western Sydney in Australia, "as no one expected to detect these object at radio wavelengths and with the present generation of radio telescopes."

The team was so surprised, they held up their findings for three years until they were completely sure that the objects they spotted were in fact planetary nebulas, Filipovic said.

Some of the 15 newly discovered planetary nebulas in the Magellanic Clouds are three times brighter than any of their Milky Way cousins. But to see them in greater detail astronomers will need the power of a coming radio telescope ? the Square Kilometre Array planned for the deserts of Western Australia.

The new findings is reported in the journal Monthly Notices of the Royal Astronomical Society.

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