It first gained notice as a strong radio source, and eventually deep images revealed a hot optical nebula at the location.

The remnant's spectrum shows no detectable lines of hydrogen and helium and the presence of only oxygen and neon.

The assumption is that a massive star burned through its hydrogen, producing oxygen and neon, and exploded before processing any heavier elements.

It must have taken place relatively recently, as the oxygen and neon have not yet mixed with the interstellar hydrogen.

Murdin, Paul, and David Allen, Catalog of the Universe, pp.