A nucleosynthesis process in which chemical elements heavier than zinc are created through the intense bombardment of other elements by neutrons in rapid succession. The essential feature of the r-pro
cess is the release of great numbers of neutrons in a very short time (less than 100 seconds). The r-process is a 'rapid' version of the s-process, occurring in supernova core collapse and possibly when a neutron star merges with a black hole in a binary star.
A member of a large class of pulsating stars of type A2-F6 with periods less than 1 day. They are similar to Cepheids, except that their periods are much shorter and are less luminous. RR Lyrae stars
belong to Population II and are often found in globular clusters (hence one of their older names cluster variables) or elsewhere in the galactic halo. They are used as distance indicators (standard candle) out to more than 200 kpc.