Five light-years across, it was once a sun-like star’s outer atmosphere expelled thousands of years ago. Abell 39 allows astronomers to accurately estimate how much relative material is actually absorbing and emitting light.
Observations indicate that Abell 39 contains only about half of the oxygen found in the Sun, an intriguing but not surprising confirmation of the chemical differences between stars. The reason why the central star is slightly off center by 0.1 light-years is currently unknown.
Several galaxies millions of light years away can be seen through and around the spectral nebula.