Arp-Madore_1
Arp-Madore 1
Globular cluster in the constellation Horologium
Arp-Madore 1 (also known as AM 1) is a globular cluster visible in the constellation Horologium, located 123.3 kiloparsecs (402,000 light-years) away from Earth.[2] It is one of the most distant known globular clusters of the Milky Way galaxy's halo;[3][4] its distance gives it interest as a test case for gravitational theories.[5] AM 1 has a visual magnitude of 15.07.[6]
It is named after Halton Arp and Barry F. Madore, who identified it as a distant globular cluster in 1979, using the UK Schmidt Telescope,[7] after previous researchers at the European Southern Observatory had observed its existence but not its classification.[8]