- Theta Eridani, Latinized from θ Eridani, is a binary system in the constellation of Eridanus with a combined apparent magnitude of 2.88. Its two components are designated θ1 Eridani, formally named Acamar /ˈækəmɑːr/ (the traditional name of the system), and θ2 Eridani. The system’s distance from the Sun based on parallax measurements is approximately 165 light-years.