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Horsehead Nebula: Definition, Facts

ByWill Kalif Posted on Updated on

The Horsehead Nebula is a type of space cloud called a dark nebula. This nebula is part of the Orion Molecular Cloud Complex, which is a dense cloud of gas and dust. The Horsehead Nebula has the catalog number IC 434, and it resides within the emission nebula IC 434. Dark nebulae are regions where cold, dark clouds of gas and dust block light from behind. It is otherwise known as Barnard 33, which is one of the Barnard objects. 

The shape of the Horsehead Nebula resembles a horse’s head, earning it the name. As a prominent feature of the Orion Molecular Cloud Complex, it is a well-known photodissociation region. 

What is the definition of the Horsehead Nebula?

The Horsehead Nebula is part of the Orion Molecular Cloud Complex, located in the constellation Orion. It is a dark nebula, which is a cold cloud of dust and gas, alternatively known as Barnard 33 or B33. The Horsehead Nebula appears at the edge of IC 434 and within Lynds 1630.

The pale pink glow of the nebula is of a swathe of ionised hydrogen, which forms an emission nebula. The ionized gas is lit from within by young and hot stars. A dark cloud contains interstellar dust, forming a dark nebula and spanning several light years. The dust absorbs light from the ionized cloud behind it. Lynds 1630 is a dense dust cloud, known as Barnard 33, where the ionised hydrogen is within the cloud. New stars are born within this dense molecular cloud, making it a star-forming region. The Horsehead Nebula is part of the Orion B molecular cloud, which is 1,300 light-years distant and located in the constellation Orion. The Orion B molecular cloud is one of the closest to the Sun. IC 434 is illuminated by Sigma Orionis, and the Horsehead Nebula is part of IC 434. Williamina Fleming, a Scottish astronomer, contributed to the study of these celestial objects.

Is the Horsehead Nebula visible from Earth?

The Horsehead Nebula is not visible from Earth due to light pollution.  The Euclid telescope observes the Horsehead Nebula in visible light.

How many stars are in the Horsehead Nebula?

The Horsehead Nebula contains a multitude of stars and active star formation is taking place in its dense dust. This nebula is a vast star-forming region within the constellation Orion. Protostars lie at the nebula’s western limb, where star formation is occurring in the dark cloud. A study identified five candidate protostars and two bona fide young stellar objects in this region. These stars are obscured by the dark nebula, which appears as one bright star when observed from Earth. The Orion Molecular Cloud, referred to as IC 434, spans several light years and includes multiple dark nebulae. It is a multiple system of five stars, all of which are in the process of forming within the molecular cloud.

What are the Horsehead Nebula and Flame Nebula?

The Horsehead Nebula is isolated from the Flame Nebula. The Flame Nebula is located near the Horsehead Nebula. Both are dark nebulae. The Flame Nebula is part of the Orion Molecular Cloud Complex, designated as Sh2-277 and NGC 2024. The Flame Nebula is an emission nebula located in the constellation Orion. It is part of the Orion B cloud and lies within the larger Orion Molecular Cloud Complex. The Flame Nebula is located east of Alnitak, which appears very close to it. Alnitak is not physically associated with the Flame Nebula. The Flame Nebula contains a young cluster of stars and IRS 2b

The Horsehead Nebula projects in front of IC 434, which stretches across approximately 40 light-years. The Flame Nebula is fainter than the Horsehead Nebula. The Horsehead Nebula is located on the other side of Alnitak, near the Orion Nebula, which is a deep-sky object in the constellation Orion. 

What are some interesting facts about the Horsehead Nebula?

Some interesting facts about the Horsehead Nebula are presented below.

  • The Horsehead Nebula lies in the constellation Orion as part of the Orion Molecular Cloud Complex, south of Zeta Orionis and Alnitak.
  • The base of the Horsehead Nebula sits south of the star Alnitak and contains gases and molecules.
  • The Horsehead Nebula is associated with Sigma Orionis.
  • The Horsehead Nebula is known as Barnard 33.
  • Surrounded by IC 434, the Horsehead Nebula is formed from a tendril of dust. 
  • The Horsehead Nebula is a dark nebula created due to a dense dust cloud called Lynds 1630 which blocks light and stars, creating darkness. 
  • The area around the Horsehead Nebula seems to show the nebula surfing across a glowing strip of hydrogen gas. 
  • Silhouetted against the pale pink glow of the nebula, the structure of the Horsehead Nebula resembles the head of a horse. 
  • The Horsehead Nebula is tall and has years left before it will be dispersed by ultraviolet light.

Will Kalif is an amateur astronomer at TelescopeNerd.com. Will is an author of the book "See It With A Small Telescope". Will Kalif has been passionate about telescopes and the wonders of the night sky ever since he received his first telescope as a teenager. And for several decades now he has been making and using his own telescopes and helping other people to also enjoy the various things that can be seen on a dark and starry night.