- 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.
- Thomas Jefferson (Wikipedia)
Thomas Jefferson (April 13, 1743 – July 4, 1826) was an American statesman, planter, diplomat, lawyer, architect, philosopher, and Founding Father who served as the third president of the United States from 1801 to 1809. He was the primary author of the Declaration of Independence. Following the American Revolutionary War and before becoming president in 1801, Jefferson was the nation’s first U.S. secretary of state under George Washington and then the nation’s second vice president under John Adams. Jefferson was a leading proponent of democracy, republicanism, and natural rights, and he produced formative documents and decisions at the state, national, and international levels.