Perhaps the most recognisable constellation in the night sky is Orion the hunter. Look closely at the three bright orbs lined up below his belt – his sword. The middle one isn’t a star, but an entire nebula, and parts of it have been invisible to researchers until recently.
Filaments in red inside the Orion nebula. Image: ESO/H. Drass/ALMA (ESO/NAOJ/NRAO)/A. Hacar (ESO)
Scientists using the Atacama Large Millimetre/submillimeter Array (ALMA) in Chile and the IRAM 30m telescope in Spain have revealed a new view of the famous Orion Nebula. The observations let researchers identify a network of gas organised in relatively thin, tangled filaments. The result was new science and an incredible mosaic of images:
The entire picture with all of the filaments. Image: ESO/H. Drass/ALMA (ESO/NAOJ/NRAO)/A. Hacar (ESO)
“The detection of fibres in Orion opens a new window on the description of the internal gas structure in massive clouds,” the authors wrote in the paper published recently in Astronomy and Astrophysics.
Nebulae are enormous regions of gas thought to be stellar nurseries – places where the gas coalesces into new stars. The Orion Nebula is around 1350 light years away and visible as a star-sized smudge to the naked eye. But if you could see all of it, the whole system would appear to be twice the size of the Moon in the sky.
Much of the system can’t be seen without the right tools. ALMA and IRAM and other newer telescopes can capture light at just the right wavelength to make these images.
The same image as above, with the filaments traced out. Graphic: Hacar et al (Astronomy & Astrophysics 2018)
Scientists first spotted these filaments around a different nebula back in 2013 and have since spotted them around other star-forming clouds. The new observations allowed them to identify 55 filaments around Orion, according to the paper.
Researchers aren’t quite sure why dense gas arranges itself in this way – perhaps the gas is simply organising itself based on the local gravitational field. But it seems to be the preferred organisation pattern in nebulae. The scientists write: “The widespread detection of fibres seems to reflect the preferred organisation mechanism for the dense molecular gas within clouds.”
Stars have to form somehow, and studying nebulae like Orion could hold the secrets to their births.