Astronomers capture the most detailed image ever of a star formation zone in Orion's 'sword'

The new images will help to validate upcoming James Webb images of the same region of space.
Chris Young
The observation of Orion's 'sword'.
The observation of Orion's 'sword'.

Source: Habart et al./W. M. Keck Observatory 

Astronomers using the W. M. Keck Observatory on Hawaiʻi Island captured the most detailed images ever taken of the region of space where the Orion constellation is constantly hit by ultraviolet (UV) radiation emanating from enormous but relatively young stars.

The region, called a Photo-Dissociation Region (PDR), is found in the Orion Bar within the Orion Nebula, an active star nursery 1,350 light years away from Earth, a press statement reveals. Viewed as part of the Orion constellation, it is located in the middle of the "sword" hanging from Orion's "belt".

The new observations provide new insight into the process of planet and star formation. They will be used to validate upcoming James Webb Space Telescope observations that will peer even further into the relatively nearby region of space.

The 'sharpest images of the Orion Bar ever'

"It was thrilling being the first, together with my colleagues of the 'PDRs4All' James Webb Space Telescope team, to see the sharpest images of the Orion Bar ever taken in the near-infrared," explained Carlos Alvarez, a staff astronomer at Keck Observatory and co-author of the study.

The researchers, whose work will be published in the journal Astronomy & Astrophysics, and is available in preprint format on, say the Orion Nebula is the closest massive star formation region to Earth, meaning that this investigation into its PDR — the region heated by starlight — could provide valuable clues about the way stars and planets are formed.

"Observing photo-dissociation regions is like looking into our past," said Emilie Habart, an Institut d'Astrophysique Spatiale associate professor at Paris-Saclay University and the lead author of a paper on this study. "These regions are important because they allow us to understand how young stars influence the gas and dust cloud they are born in, particularly sites where stars, like the sun, form."

The scientists used the Keck Observatory's second-generation Near-Infrared Camera (NIRC2) in combination with the Keck II telescope's adaptive optics system to image Orion's PDR in unprecedented detail. This allowed them to distinguish between the Orion Bar's different substructures, including its filaments and ridges.

"Never before have we been able to observe at a small scale how interstellar matter structures depend on their environments, particularly how planetary systems could form in environments strongly irradiated by massive stars," Habart explained. "This may allow us to better understand the heritage of the interstellar medium in planetary systems, namely our origins."

James Webb will observe Orion's 'sword' in the coming weeks

The new research is also informing upcoming observations that will be carried out by the James Webb Space Telescope (JWST), which started scientific operations in July. James Webb is expected to observe the Orion Bar in the coming weeks, and the Keck Observatory images will play a role in validating those images.

"One of the most exciting aspects of this work is seeing Keck play a fundamental role in the JWST era," said Alvarez. "JWST will be able to dive deeper into the Orion Bar and other PDRs, and Keck will be instrumental in validating JWST's early science results. Together, the two telescopes can provide unique insight into the characteristics of the gas and chemical composition of PDRs, which will help us understand the nature of these fascinating star-blasted regions."

The new Keck Observatory images, alongside the upcoming James Web images, will help to better understand the important role of cold molecular gas in star formation as it will allow scientists to map how gas in the PDR changes from hot ionized gas, to warm atomic, to cold molecular gas. Ultimately, this will give us a better understanding of the processes that allowed Earth to form in our solar system and life to flourish on the tiny speck we call home.

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