Orion B filaments
The Orion B molecular cloud, with the Horsehead nebula in the upper right corner, as traced by the 13CO molecule observed with the IRAM 30-m telescope. The brightness represents the density of the gas, while the colours encode its motions: regions depicted in blue are approaching us, regions in red are receding.​​​

More stars will surround the Horsehead in the future, new study reveals

​​​Why are so few stars born around the Horsehead Nebula, even though all the conditions seem to be there? That question can now answer a Chalmers-led research team.
The Horsehead Nebula in the constellation Orion is one of the most famous shapes in the sky, as was recently seen in Australia’s spectacular performance in the Eurovision Song Contest

The Horsehead is located in Orion B, one of two main molecular clouds in the constellation Orion’s “belt”.
In this cloud, astronomers believe that many new stars could be born - but on the contrary, the birth rate is unusually low. In a new study, a research team led by Chalmers astronomer Jan Orkisz explains why: the cosmic filaments in Orion B are still young, and star formation in the filaments might become more active in the future.

– Comparing the filaments of Orion B with other clouds, such as the nearby cloud Orion A where the filaments are more massive, gravitationally bound and actively forming stars, can show that Orion B is a very peculiar cloud. Despite its size and mass, it is known for its very low star formation activity, says Jan Orkisz, at the Department of Space, Earth and Environment at Chalmers. 
– However, we rather interpret it as the fact that Orion B is simply a cloud in an early evolutionary stage: its filamentary architecture already shows similarities with more evolved environments, and star formation in the filaments might become more active in the future. If this is the case, then it also shows that filaments play an important part early in the evolution of interstellar matter, as they start to structure the gas before gravity has taken over, says Jan.

Further studies of the Orion Molecular Cloud Complex can thus help understanding all the stages of the cycle through which the Galactic matter goes.

Image credits: 
Top image: IRAM, Institut de Radioastronomie Millimétrique. ​
Image of the Horsehead Nebula: Ken Crawford. (Click to see high resolution image).
Portrait Jan Orkisz: Christian Löwhagen

Published: Wed 22 May 2019. Modified: Wed 29 May 2019