Cas A is the strongest radio source in the sky beyond our solar system, and was among the first discrete sources to be found, in 1947.
The central star cluster is dominated by a number of discrete sources; one of them, IRS16, has traditionally been considered the core of the cluster.
This may occur when a sensitivity analysis has to performed retrospectively, perhaps using data from an optimisation or uncertainty analysis, or when data comes from a discrete source.
However, it is now thought that about 80% of the emission comes from discrete sources such as white dwarfs and stars with active coronae.
Later experiments, both in orbit and on the ground have identified numerous discrete sources of cosmic gamma rays in our Galaxy and beyond.
Nonpoint source pollution refers to diffuse contamination that does not originate from a single discrete source.
Unfortunately, all attempts to locate these discrete sources with remote sensing probes have been unsuccessful.
In addition to discrete sources which stand out against the sky, there is good evidence for a diffuse X-ray background.
Each of the 18 cases are designed to be a "discrete historical source for an area of learning".
There is no discrete source.