The Horsehead Nebula is a cloud of thick dust and gasses near the star Alnitak in the constellation Orion’s Belt. The Horsehead Nebula is particularly well-loved by professional astronomers and amateur space fans because of its uncanny resemblance to a horse’s head.
The unmistakable silhouette, while easy to spot when images of the nebula have been manipulated by astrophotography and image enhancement tools, is tough to spot with the naked eye, especially in today’s era of light pollution.
In this article, we aim to break down what nebulae are, how they form, and the history of the famous Horsehead Nebula, from its specific formation to its discovery and prominence in the scientific literature.
While it’s quite a famous visual phenomenon in our solar system, we acknowledge that a good portion of our readership might never have heard of it. So, we aim to give a complete and comprehensive breakdown of the Nebula and just what makes it so special.
What Is a Nebula and How Does It Form?
Nebulae, as we mentioned earlier, are giant clouds of thick dust and gasses that form in space. They can develop in various ways, including due to a star exploding. When a star explodes, it exudes enormous force into space and the surrounding area. It also releases many materials, including carbon, hydrogen, and helium.
After the initial shock of the explosion, the dark dust eventually settles into the nebula form. Once this occurs, a planetary nebula can last for over 20,000 years. While this might sound like a long time, in truth, it’s considered to be a very short occurrence in terms of space timelines. Considering how old the universe is, we’re sure this makes sense.
Another fascinating fact about nebulas is that, over time, the dust that makes them up can clump together into bigger and bigger lumps. As this occurs, the resulting gravitational pull between objects grows as well. Eventually, stars can form from nebulae, showcasing a life cycle amongst the stars. This happens when the clump of dust and gas gets so big that it collapses in on itself and gets ultra-hot, which forms the core of a new star.
A Breakdown of the Horsehead Nebula
The Horsehead Nebula is known by many names, including Barnard 33 or B33. (Let’s face it: Horsehead Nebula is quite a mouthful.) It is situated along Orion’s Belt, one of the most famous constellations in the night sky. While we know a lot about B33 today and the different components that make it up, when we begin to examine its origins, things get a little bit hazier.
B33 lies approximately 1,375 lightyears away from us on planet Earth. The nebula itself is made up of cold gas and dust. We can theorize that the nebula is made up primarily of hydrogen and helium, as is typical of identifiable nebulae. One thing that makes B33 particularly fascinating is understanding why we can see it in the first place.
See, the dark nebula doesn’t emit any light of its own. The only reason we can see it is because of the bright star system behind it, known as Sigma Orionis. This star system is made up of over ten stars that are all less than two million years old. However, these stars are exceptionally bright because of their spectral type – this, as the name would imply, refers to the classification of stars that they fall under.
At B33’s base, scientists have detected stars that are still in the process of forming. These very young stars will have a lifespan of many millennia, but the Horsehead Nebula may be on its way out before they can be fully developed.
Estimates for the nebula’s lifespan currently range between five million and five billion years, meaning it has a long way to go before the gas it’s made of fully dissipates. This occurs during photodissociation, where the radiation of nearby stars causes the dust cloud to be torn apart by sheer force.
Does the Nebula Emit Light?
While the Horsehead Nebula certainly appears to emit light, the truth is that the only light you can see is coming from the stars behind the Nebula. The Nebula is a mixture of cold gasses and dust that barely emits heat.
While logically, you might be questioning why we aren’t simply stating that it doesn’t emit any heat, this would be false. Because those gasses contain some semblance of matter, there is energy stored within the Nebula, and therefore some small amounts of heat.
While it might not seem like very much heat, one has to remember that you are comparing trace amounts of heat against the vast emptiness and cold nature of space itself.
The radiation emitted by stars would be ultra-deadly to any human or animal that came close enough. It is equally deadly to any unfortunate nebulae that might be close enough to feel its effects. However, nebulae are far more resilient to the effects of radiation than you or I – again, it will take millions of years for the negative effects of it to be felt.
Humans Discovering the Horsehead Nebula
Many people have claimed to be the discoverer of the Horsehead Nebula over the ages. In truth, there is no way to know who deserves the title of its discoverer. However, the generally held consensus is that William Herschel, a British astronomer, discovered it while spying through his telescope in 1811.
He noted several objects that were vague to researchers and other scientists and resulted in not much ado about anything for some time. In his writings, Herschel recorded seeing over 52 nebulae while searching the night skies, but most scientists, being unable to confirm his sightings, paid him little to no heed.
It wasn’t until an amateur astronomer from Wales named Isaac Roberts could photograph and identify some of the nebulous sights himself that Herschel would receive any real scientific credit. Unfortunately for him, Roberts didn’t photograph anything until 1902. However, Herschel’s discoveries will still live on in the history books, and our knowledge of B33 was given a legitimate foundation.
Roberts didn’t realize what he had found when he photographed B33. He initially misidentified it as some vague visual blunder that couldn’t be much ascribed to any real scientific phenomenon, so he dismissed it and moved on with his life. As a result, he, unfortunately, stayed an amateur in the field and never really did anything of note in the scientific community for the rest of his life.
The person who truly put the famous Horsehead Nebula in the history books was Scottish astronomer Williamina Fleming, a famed “human computer” working at the Harvard College Observatory when she identified the Nebula from one of her employers’ photographic plates.
Her employer, a learned man named Edward Charles Pickering, assured her that she had found something worth noting, and the Horsehead Nebula, or B33, was recorded for the first time in history.
Understanding the Horsehead Nebula
We hope this article helped you learn more about this mysterious yet famous object in our solar system, the Horsehead Nebula. Identifying astronomical objects can be difficult on its own, but knowing the history and scientific explanations is quite another matter.
We hope that we were able to shed a little more light on this dark subject. Perhaps now that you know what you’re looking for, you can spot it on a clear night.
Remember to look for the bright spots between the second and third stars on the constellation Orion’s Belt. If you look closely and peer with all your might, you might be able to make out a tiny horse head rearing back and neighing into the cosmos. Good luck on your sightseeing expeditions, and keep your eyes to the heavens.