- Baby boomers (Wikipedia)
Baby boomers, often shortened to boomers, are the demographic cohort preceded by the Silent Generation and followed by Generation X. The generation is often defined as people born from 1946 to 1964 during the mid-20th century baby boom. The dates, the demographic context, and the cultural identifiers may vary by country. Most baby boomers are the children of either the Greatest Generation or the Silent Generation, and are often parents of Millennials.
- Open cluster (Wikipedia)
An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and many more are thought to exist. Each one is loosely bound by mutual gravitational attraction and becomes disrupted by close encounters with other clusters and clouds of gas as they orbit the Galactic Center. This can result in a loss of cluster members through internal close encounters and a dispersion into the main body of the galaxy. Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for longer. Open clusters have been found only in spiral and irregular galaxies, in which active star formation is occurring.