- Atoms are the basic particles of the chemical elements and the fundamental building blocks of matter. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element.
- Delta Cephei (stars.astro.illinois.edu)
DELTA CEP (Delta Cephei). Surely among the most famed of all stars, fourth magnitude (4.1 or thereabouts) Delta Cephei, set at the southeastern corner of dim Cepheus (the King), does not even have a proper name. It is, however, the only star that has given its constellation name over to represent a whole class of stars, the “Cepheids.”