Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the bright reflection nebula known as Messier 78!
During the 18th century, famed French astronomer Charles Messier noticed the presence of several “nebulous objects” while surveying the night sky. Originally mistaking these objects for comets, he began to catalog them so that others would not make the same mistake. Today, the resulting list (known as the Messier Catalog) includes over 100 objects and is one of the most influential catalogs of Deep Space Objects.
On Earth, dust can be pretty mundane. But in space, dust can be beautiful, especially when the dust reflects starlight – and even more so when we have the chance to see the reflections in different wavelengths. Here in NGC 2068, also called Messier 78, this dazzling submillimetre-wavelength view from the Atacama Pathfinder Experiment (APEX) telescope Dust shows the glow of interstellar dust grains, pointing the way to where new stars are being formed.
This reflection nebula lies just to the north of Orion’s Belt. When seen in visible light glimmers in a pale blue glow of starlight, but much of the light is blocked by the dust. In this image, the APEX observations are overlaid on the visible-light image in orange. APEX’s view reveals the gentle glow of dense cold clumps of dust, some of which are even colder than -250 C.
Compare the new image with this earlier, visible light image of M78.
One filament seen by APEX appears in visible light as a dark lane of dust cutting across Messier 78. This tells us that the dense dust lies in front of the reflection nebula, blocking its bluish light. Another prominent region of glowing dust seen by APEX overlaps with the visible light from Messier 78 at its lower edge. The lack of a corresponding dark dust lane in the visible light image tells us that this dense region of dust must lie behind the reflection nebula.
Observations of the gas in these clouds reveal gas flowing at high velocity out of some of the dense clumps. These outflows are ejected from young stars while the star is still forming from the surrounding cloud. Their presence is therefore evidence that these clumps are actively forming stars.
At the top of the image is another reflection nebula, NGC 2071. While the lower regions in this image contain only low-mass young stars, NGC 2071 contains a more massive young star with an estimated mass five times that of the Sun, located in the brightest peak seen in the APEX observations.
Here’s another “Hidden Treasure” from the European Southern Observatory, from the astrophotography competition where amateurs create images from unused ESO data. In this new image of Messier 78, brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light and creating what is called a reflection nebula. Almost like fog around a street light, a reflection nebula shines only with the light from an embedded source that illuminates the dust. This image was taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. Comparing this image with others previously taken of Messier 78 shows that remarkably, this object has changed significantly in the last ten years.
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.
For those of you who want to take a look on your own:
Right Ascension: 05:46.7
Distance: 1.6 (kly)
Visual Brightness: Magnitude 8.3
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 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.
But this object has changed significantly in the last ten years. In February 2004 the experienced amateur observer Jay McNeil took an image of this region with a 75 mm 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 H-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.