- Date: December 2010/2016
- Location: Grasberg/Otterstein, Germany
- Camera: Atik 460EXM, Atik 4000 M
- Optics: 14″-Newton/12″-Newton
- Mount: Alt 7 ADN/Alt 5 ADN
- Filters: LRGB
- Exposure: L: 22 x 10 min, R, G, B: 9 x 5 min
The nebula Messier 78 takes centre stage in this image taken by Gerald Willems from Germany, while the stars powering the bright display take a backseat. The brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light.
Messier 78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionise the gas to make it glow — its dust particles simply reflect the starlight that falls on them. Despite this, Messier 78 can easily be observed with a small telescope, being one of the brightest reflection nebulae in the sky. It lies about 1350 light-years away in the constellation of Orion (The Hunter) and can be found northeast of the easternmost star of Orion’s belt.
The pale blue tint seen in the nebula in this picture is an accurate representation of its dominant colour. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles that they contain: the shorter wavelength of blue light is scattered more efficiently than the longer wavelength red light.
Two bright stars, HD 38563A and HD 38563B, are the main powerhouses behind Messier 78. However, the nebula is home to many more stars, including a collection of about 45 low mass, young stars (less than 10 million years old) in which the cores are still too cool for hydrogen fusion to start, known as T Tauri stars. Studying T Tauri stars is important for understanding the early stages of star formation and how planetary systems are created.
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