Messier 103 is an open star cluster located in the constellation Cassiopeia. It was discovered by the astronomer Pierre Méchain in 1781 and later included in the Messier catalog by Charles Messier. The cluster is approximately 8,000 light-years away from Earth and contains around 170 stars. The stars in Messier 103 are relatively young, with an estimated age of about 25 million years. The cluster is notable for its bright blue stars, which are more massive and hotter than the Sun. Observing Messier 103 can be done with binoculars or small telescopes, making it accessible to amateur astronomers.