As promised, we will continue this week with the Orion Constellation. If you need to catch up start with Gazing Deep into the Orion Constellation and then read Gazing Deeper into the Orion Constellation (Image Gallery).
Horsehead Nebula
Friday, March 4, 2011: The Canada-France-Hawaii Telescope produced this stunning image of the well-known Horsehead Nebula. It is part of an enormous cloud of molecular gas and dust obscuring background light from nearby emission nebula IC 434, producing the silhouette.
–Tom Chao
CREDIT: Canada-France-Hawaii Telescope/Coelum
The dark Horsehead Nebula (Barnard 33) is about 1,500 light-years away and it’s right in front of the much lighter IC 434 nebula. Unlike the reflection nebula Messier 78, the Horsehead Nebula emits its own light. Emission nebulae emit their own light rather than reflecting light from nearby stars. Type B and Type O stars that are close by shine energetic UV radiation onto the nebula that knocks the electrons right off of the Hydrogen molecules (ionization). This leaves the Hydrogen molecules without their electrons (and they are now just nuclei) and the electrons are whizzing around without a molecule. The electrons collide with the left over Hydrogen nuclei and once again create whole molecules that are now in an excited state which cause the molecules to emit red light.
Another really cool thing about emission nebulae is that their form is dependent on how the UV radiation from the nearby stars interacts with the hydrogen as if the stars were molding the nebula to suit their fancy. It’s amazing how we can see something as relatable as a horse’s head in a cloud of gas which is the very reason why this nebula has become one of the most familiar objects in the night sky.
Barnard’s Loop Taken with Canon 350D and 70-200L Lens. RGB and Hydrogen alpha light.
Credit: Hunter Wilson
Barnard’s loop is a bubble shaped emission nebula that surrounds the Horsehead Nebula about 1,500 Light-years away. It is speculated that Barnard’s Loop may be a remnant of a series supernovae that happened a few million years ago which could definitely explain how AE Aurigae, Mu Columbae, and 53 Arietis were ejected from the area in the same time frame.
The Flame Nebula
The Flame Nebula taken by WISE, NASA’s Wide-field Infrared Survey Explorer.
Image Credit: NASA/JPL-Caltech/UCLA
The Flame Nebula (NGC 2024 and Sh2-277) is an emission nebula and a massive star forming region that is about 1,500 light-years away. There is a cluster of stars that is in the process of forming inside of the nebula. The cluster isn’t fully developed and it is said to be less than 1 million years old.
The 37 Cluster
Image Credit: ScottRak
The Cosmic 37 is so nicknamed because of the uncanny resemblance this cluster has to the said numbers. This 8 million year old open cluster is about 3,600 Light-years away and spans a mere 7 Light-years across making it a pretty small cluster. This cluster isn’t actually a part of the Orion Molecular Cloud Complex, but it’s still associated with the region.
NGC 2023
This picture was created from multiple images taken with the Wide Field Camera of Hubble’s Advanced Camera for Surveys.
Image Credit: ESA/Hubble & NASA
This beautiful nebula is hidden away in a very famous area of sky. It is right next to the Flame and Horsehead Nebulae and it is often included in photos of those nebulae even if it isn’t mentioned. NGC 2023 is the home of a massive young B-type star that provides most of the illumination, making this nebula (mostly) a reflection nebula. The star is incredibly bright and it makes this nebula very easy to see, it even created a flare on the above photo. This nebula also has Herbig-Haro objects (the bright green spots in the upper right side of the image) which are areas where there is a process similar to that of an emission nebula making it glow. This is caused by a jet of gas (polar jets) that young stars eject into the nebula around it, and it is going so fast (hundreds of kilometers per second) that it creates shock waves that produce light.
Closing
I can remember finding Orion in the sky as a child and I had no idea how rich this large patch of sky is with potential knowledge. We are even learning new things about one of the most well-known regions of space – we’ve recently discovered that two massive groupings of stars within the Orion Nebula are actually completely separate structures that are well in front of the nebula. This discovery will cause astronomers to revise what we currently know about the structure to accommodate this morsel of knowledge.
Sources:
Canada-France-Hawaii Telescope
Stunning New Look at Reflection Nebula Messier 78
Just Another Face in the Crowd
Hunter Wilson Astrophotography
Wide-field Infrared Survey Explorer
Spectacular Photo of Orion Space Cloud Snapped by Night Sky Observers
Checkmate… Capturing the “Steed of Dust”
Orion Revisited: Astronomers Find New Star Cluster in Front of the Orion Nebula
