Reflected glory in nebula M78
The ultraviolet radiation from the stars that illuminate M78 is not intense enough to ionize the gas to make it glow — its dust particles simply reflect the starlight that falls on them.
The nebula M78 takes center stage in this image taken with the Wide Field Imager on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile, 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. Igor Chekalin from Russia was the overall winner of the European Southern Observatory’s (ESO) Hidden Treasures 2010 astrophotography competition with his image of this stunning object.
M78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionize the gas to make it glow — its dust particles simply reflect the starlight that falls on them. Despite this, M78 is easily observable through a small telescope because it is one of the brightest reflection nebulae in the sky. It lies about 1,350 light-years away in the constellation Orion The Hunter, and it 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 color. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles they contain — the shorter wavelength of blue light is scattered more efficiently than the longer wavelength of red light.
This image contains many other striking features apart from the glowing nebula. A thick band of obscuring dust stretches across the image from the upper left to the lower right, blocking the light from background stars. In the bottom right corner, many curious pink structures are also visible, which are created by jets of material being ejected from stars that have recently formed and are still buried deep in dust clouds.
Two bright stars, HD 38563A and HD 38563B, are the main powerhouses behind M78. 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.
Remarkably, this complex of nebulae has also changed significantly in the past 10 years. In February 2004, the experienced amateur observer Jay McNeil took an image of this region with a 75mm telescope and was surprised to see a bright nebula — the prominent fan-shaped feature near the bottom of this picture — where nothing was seen on most earlier images. This object is now known as McNeil's Nebula, and it appears to be a highly variable reflection nebula around a young star.
This color picture was created from many monochrome exposures taken through blue, yellow/green, and red filters, supplemented by exposures through an Hydrogen-alpha filter that shows light from glowing hydrogen gas. The total exposure times were 9, 9, 17.5, and 15.5 minutes per filter, respectively.