NGC 6540 is an open star cluster located in the constellation Sagittarius. It was discovered by the astronomer William Herschel in 1784. This cluster is approximately 4,500 light-years away from Earth and contains around 50 stars, which are relatively young compared to other star clusters. The stars in NGC 6540 are loosely bound by gravity and are spread out over a region about 10 light-years in diameter. The cluster is notable for its bright stars, which are primarily of spectral types B and A, indicating they are hot and luminous.