Phosphorus in a Supernova Remnant
A three-color image of the young supernova remnant Cassiopeia A. Astronomers have concluded that phosphorus was produced in this explosion - in good agreement with models. Red shows infrared emission from iron, while green and blue are images at X-ray wavelengths taken by the Chandra X-ray Observatory. The white lines indicate the locations where the elements were studied; the white scale at the bottom corresponds to a length of 3.3 light-years.
The element phosphorus is an indispensable ingredient for life along with carbon, oxygen, nitrogen, hydrogen, and sulfur. But phosphorus is much less abundant in the universe than these other elements -- in the solar system it is about three and one-half million times less common than hydrogen. Hence the mechanism(s) for making it are of particular interest to astronomers. All the elements except for hydrogen and some helium (which were made in the big bang) are the by-products of nuclear processing in stars. Scientists think that phosphorus is formed mainly in massive stars (more than about eight solar masses). These stars end their lives as supernova explosions, and current models conclude that most phosphorus is made either during a stage just prior to the explosion, or in layers during the explosion itself.
Freshly synthesized phosphorus should be present in the remnants of supernovae from massive stars if these theories are correct. CfA astronomer John Raymond and his colleagues studied the phosphorus in the remnant Cassiopeia A, which lies about eleven light-years away and was made in an explosive event in the year 1681. The team examined the near-infrared emission line of phosphorus at multiple locations around the remnant, and used its strength compared to other species, as well as the motions of the gas, to describe the processes responsible. The astronomers are able to confirm the models and, at least least in the case of this supernova remnant, refine the details of the key mechanisms responsible.
"Phosphorus in the Young Supernova Remnant Cassiopeia A," Koo, B-C, Lee, Y-H, Moon, D-S, Yoon, S-C, and Raymond, J., Science, 342, 1346, 2013