In the depth of this universe, imagine a cosmic background far far away where the stars are born in the stellar nurseries known as Nebulae. In these starry nurseries, something extraordinary happens. There is a magical sight that scientists just can’t get enough of – the Herbig Haro objects. These Herbig Haro objects give us a peek into the incredible journey of how stars are being born. In this blog, we will cover all that you need to know about these mysterious Herbig Haro objects.

The Herbig Haro objects commonly known as HH objects, are found in star forming regions. They are named after astronomers George Herbig and Guillermo Haro who independently discovered them in the mid 20th century. What makes them interesting are the bright luminous patches just looking like colorful fireworks within the nebulous region. But wait, how does it even happen? Let’s get into the depths!

How did Herbig Haro objects form?
Just like humans, stars have a lifespan too! Stars begin their life from the region of dense clouds of gas and dust, called molecular clouds or nebulae. Deep within this cosmic cradle of molecular clouds, the journey of Herbig Haro objects begins, but with a twist! Within this dense molecular cloud, gravity starts to pull the tiny particles of gas together, causing them to collapse. As a result, the molecular cloud’s temperature rises and stops the further collapse by establishing a hydrostatic equilibrium, forming a protostar.
Now this stage is an infant stage of a star where it is feisty and hungry. As an infant needs food to grow,this protostar feeds on the surrounding matter to grow. This protostar acceretes more and more matter and emits huge, narrow jets of intense radiation along its polar axis.

These jets travel thousands of kilometers to clear away the gas and dust around them, making room for the star to shine. But the fun doesn’t stop here! These jets produce shock waves when they collide with the surrounding gas, heating it up and giving it a dazzling glow similar to neon lights in the sky. These are the Herbig Haro objects (HH objects), the glowing blobs of gas and dust as seen in the Infrared image (IR) of Herbig- Haro 212 captured by the European Southern Observatory’s Very Large Telescope.
Why are Herbig Haro objects important?
Herbig and Haro separately discovered a large number of objects in the Orion Nebula in the 1940s that were associated with young stars, usually a few hundred thousand years old. These were first thought to be in the T- Tauri star formation early phases. Initially, it was thought that HH objects may be the reflection nebulae that contain hot stars due to the high quantities of ionisation seen in them. But this theory was called into question by the fact that these objects did not emit infrared light.
In 1975, Schwartz proposed a theory suggesting that winds emitted by T Tauri stars could generate shock waves upon encountering the surrounding medium, resulting in the emission of visible light. It became clear that Herbig Haro objects are shock-induced events, triggered by collimated jets ejected by protostars, with the discovery of the first proto-stellar jet in HH 46/47 located about 450 parsecs away in a Bok globule near the Gum nebula. Herbig Haro objects represent only a small fraction, estimated up to 150,000, existing within our Milky Way.

Credits: NASA, ESA, CSA
The presence of Herbig Haro objects gives an insight to study the initial processes involved in Star formation. The shock waves between jets and the interstellar medium of Herbig-Haro objects serve as cosmic laboratories where one may investigate how gas particles accelerate, heat up, and get ionised. This provides a better understanding of complex dynamics in star forming regions.
Studying their chemical footprints helps to understand the chemical composition of the interstellar medium. Through spectroscopic research, astronomers may examine the abundance of various elements and compounds, offering valuable insights into the formation of galaxies. The Orion nebula, located in the Orion constellation which is nearly 1500 years away and the Pelican Nebula , nearly 1,800 light years away, in the constellation of Cygnus hosts some of the major HH objects as mentioned below.
As these objects are not visible to the naked eye, don’t miss this opportunity! You can enjoy watching this spectacular Orion Nebula and many more deep sky objects during the Astro tour to Spiti Valley with Stargazing mumbai!
Some prominent Herbig Haro Objects:
- HH 24: This Herbig Haro object is a tiny knot of incandescent gas expelled from a young stellar system, and it is situated close to the bright star Theta 1 Orionis C.
Herbig-Haro object 24
Credits: ESA/Hubble & NASA - HH 34: Herbig-Haro 34, is located in the southeast region of the Orion Nebula, this notable HH object is a massive, curving structure formed by the jets of the newborn binary star in the Orion Nebula.
Herbig Haro objects 34
Credits: NASA / ESA / Hubble - HH 505: Herbig-Haro 505, is known for its colorful and intricate look. It is an intriguing example of stellar outflow situated in the distant region of Orion Nebula.
Herbig Haro objects 505
Credits: NASA / ESA / Hubble - HH 555: Herbig Haro 555, is one of the prominent HH objects in Pelican Nebula (IC 5070) in the constellation of Cygnus. This nebula is a large emission nebula. In the following image, you can see the two long elongated faint jets emerging from a young star hidden in the dust pillar depicted by the horizontal streaks.
Herbig Haro objects 555 (HH 555)
Credits: NASA / ESA / Hubble