Messier 78

Messier 78 is a reflection nebula in the constellation Orion. It is the brightest diffuse reflection nebula in a group that includes NGC 2064, NGC 2067, and NGC 2071, all part of the Orion B molecular cloud complex. Located approximately from Earth, M78 is visible in small telescopes as a hazy patch illuminated by two B-type stars, and, of 10th and 11th magnitude. It is a popular target for amateur astronomers, who have given it the common name Casper the Friendly Ghost Nebula.

Discovery

Discovered by Pierre Méchain in 1780, M78 was included in Charles Messier's catalog of comet-like objects that same year.

Structure and composition

The nebula's dust cloud reflects light from its two central stars, making it visible. Infrared observations reveal an embedded star cluster and a hierarchy of gas clumps with core masses ranging from to. M78 hosts:

45 T Tauri stars.
17 Herbig–Haro objects.

Observations

On May 23, 2024, the European Space Agency released a high-resolution image of M78 from the Euclid mission, revealing hundreds of thousands of previously unseen objects, including substellar bodies.