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Messier 78 - a reflection nebula complex in the constellation Orion

Description of object:

In the center of our image - embedded in the dense dark molecular cloud Orion B with abundant dust and cold gas - lies a complex of several reflection nebulae. While in emission nebulae gas clouds are stimulated to glow by ionisation of high-energy stars, in reflection nebulae the gas masses only reflect the light of bright stars. Messier 78 is one of the brightest reflection nebulae in the sky and can already be observed with smaller telescopes in dark environments. The distance to the solar system is about 1500 to 1600 light years.

Messier 78 is bounded at its upper edge by a prominent arc-shaped dark cloud which apparently separates it from the adjacent nebula NGC 2067 above. In reality, however, this dark cloud lies in front of the reflection nebula complex. The two bright stars HD 38563 A and HD 38563 B produce a major part of the light that illuminates the reflection nebulae. But the nebula accommodates many more stars, among others a collection of 45 low-mass young stars, so-called T Tauri stars, which are less than 10 million years old and hide behind the dust clouds.

About 1/4 degree northeast of M 78 is NGC 2071, a region of active star formation, from where dense dust clouds extend northwest.

In the path of the dark cloud LDN 1627 in southern direction our image shows the two Herbig Haro objects HH 19 and HH 24. They are generally very young stars which repel matter clouds and then interact with surrounding dust clouds. Their color is reddish, caused by a strong emission in sulfur light (SII). HH 19 is a single star, whereas HH 24 consists of a small group of young stars.

South of HH 24 is a small, orange glowing nebula. It has the catalogue number Be 106 and contains a young T Tauri star. T-Tauri stars are extremely young stars which are less than 1 million years old. Because of their small age these stars are not yet stable and mostly irregularly variable.

Messier 78 was discovered in March 1780 by the French astronomer and geographer Pierre Méchain and was also described by Charles Messier in late 1780.

« The annotated image shows also a comparison to the size of the full moon.

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