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Young stars in the Orion Nebula are practicing birth control

Astronomers from Leiden University have discovered that the star wind from a newborn star in the Orion Nebula prevents more stars from forming in the immediate vicinity. They made the discovery with data from the SOFIA observatory. This was announced by co-author Xander Tielens during a press conference at the 233rd meeting of the American Astronomical Society in Seattle, USA. The research result will be published on 7 January in Nature.

The result is surprising because scientists thought that other processes such as exploding stars (supernovas) are largely responsible for regulating star formation. But SOFIA observations now suggest that baby stars generate star winds that blow away the basic material for star production. 

Hidden stars

SOFIA is NASA's stratospheric observatory for infrared astronomy, which makes its observations from a modified Boeing 747SP jetliner. The Orion Nebula is a nursery of stars, which has often been observed and photographed. Of all star factories, it is the closest to the earth. Veils of gas and dust make the Orion Nebula beautiful to see, but also make that the birth process of the stars is largely hidden from view. Telescopes like SOFIA can observe the infrared light that does pass through the dust clouds, and thus see star forming processes that remain hidden in optical light.

Star wind

In the heart of the Orion Nebula lies a small group of young, heavy and bright stars. The special GREAT instrument on SOFIA recorded that the strong wind of the brightest of these baby stars, Theta1 Orionis C (θ1 Ori C), has swept away a large shell of material from the cloud in which this star was born, like a snowplow sweeping a street by moving the snow to the side of the road.

'The wind is responsible for blowing a big bubble around the central stars,' explains first author and PhD student at the Leiden Observatory Cornelia Pabst. 'In the heart of the Orion Nebula he tears apart the star formation cloud and thus prevents the birth of new stars.' At the same time, the wind pushes molecular gas towards the edges of the bubble, forming new regions of densely packed material from which new stars can be formed in the future.

Speed control

The researchers used the GREAT instrument to measure the chemical fingerprint of ionised carbon. The earth's atmosphere blocks infrared light, but because SOFIA flies high (so it does not suffer from 99 percent of the water vapour in the atmosphere) they were able to study the physical properties of the star wind.

'Astronomers use GREAT like a policeman uses a radar gun,' explains Pabst's promoter, Xander Tielens (Leiden Observatory). 'Your car reflects the radio radiation and the signal tells the officer if you are driving too fast.' Similarly, astronomers use the spectral line of ionised carbon to determine the velocity of the gas through the nebula, studying the interactions between the heavy stars and the clouds in which they were born.

Space between the stars

Through this kind of research, astronomers learn more about the space between the stars that is filled with gas and dust, the so-called interstellar medium. 'Understanding how star formation interacts with the interstellar medium is important for our understanding of the origin of stars that we can study now and the stars that will be formed in the future,' says Pabst.

Scientific paper: Disruption of the Orion Molecular Core 1 by the stellar wind of the massive star θ1 Ori C. C. Pabst, R. Higgins, J.R. Goicoechea, D. Teyssier, O. Berne, E. Chambers, M. Wolfire, S. Suri, R. Guesten, J. Stutzki, U.U. Graf, C. Risacher, A.G.G.M. Tielens. http://dx.doi.org/10.1038/s41586-018-0844-1

Press release: www.astronomie.nl

Videos: https://www.sofia.usra.edu/Orion3D

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