A photograph of the Orion Nebula. Depositphotos.

Most Detailed Images of Orion’s Sword Captured by Astronomers

The Orion Nebula is the closest massive star formation region to us, and its PDR is likely to contain clues about how stars and planets form since it may be similar to our solar system's birthplace.

In a new study, researchers used the W.M. Keck Observatory on Maunakea to capture the most precise and complete image ever captured of the region where Orion gets drenched with ultraviolet (UV) radiation from massive young stars.

There is an irradiated neutral zone within the Orion Bar within the Orion Nebula, also known as the Photo-Dissociation Region (PDR), which is an active star-forming site in the middle of the “sword” hanging from Orion’s belt. The photogenic nebula is often mistaken for a star in the constellation when viewed with the naked eye; however, viewed with a telescope, it becomes a stellar nursery of gaseous gas located 1,350 light years away.

Carlos Alvarez, a staff astronomer at Keck Observatory and coauthor of the study, said he was thrilled to see the sharpest near-infrared images of the Orion Bar ever taken.

Studies of the Orion’s Nebula PDR are ideal for finding clues about how stars and planets are formed because it is the closest massive star formation region to us and might be similar to our solar system’s birthplace.

An associate professor at Paris-Saclay University and lead author of this study, Emilie Habart, said that studying photo-dissociation regions is like peering into our past.

Experts point out that these regions are important because they provide insight into how new stars influence the gas and dust clouds in which they are born, particularly those where stars like the sun are born.

The NIRC2 instrument at Keck Observatory acquired this infrared heat map of the Orion Bar. Image Credit: Habart et al./W. M. Keck Observatory.
The NIRC2 instrument at Keck Observatory acquired this infrared heat map of the Orion Bar. Image Credit: Habart et al./W. M. Keck Observatory.

Observations of these stars contributed to the planning of the Early Release Science (ERS) program for the James Webb Space Telescope (JWST) titled PDRs4All: Radiative feedback of massive stars (ID1288). The PDRs4All team used the adaptive optics system of the Keck II telescope in conjunction with the second generation Near-Infrared Camera (NIRC2) to investigate Orion’s PDR. After imaging the Orion Bar in such high detail, the researchers were able to identify and spatially resolve the different substructures formed as the nebula’s gas and dust mixture was blasted and sculpted by starlight, resulting in ridges, filaments, globules, and proplyds (externally illuminated photoevaporating disks around young stars).

The interaction between interstellar matter structures and their environment has never been observed at a small scale, particularly in environments heavily irradiated by stars, Habart noted. “This may allow us to better understand the heritage of the interstellar medium in planetary systems, namely our origins.”

It is not yet known how UV radiation from massive young stars impacts and shapes star formation in their native cloud. The stars emit large quantities of UV radiation that affect the physics and chemistry of their local environment.

In addition to revealing in detail where gas in the Orion Bar changes from hot ionized gas to warm atomic gas, the new Keck Observatory images will also provide astronomers with a better understanding of how this process happens. Because star formation requires dense, cold molecular gas, mapping, this conversion is crucial.

JWST will observe the Orion Bar in the coming weeks based on observations from Keck Observatory.

This work shows Keck’s fundamental role in the JWST era, which is one of the most exciting aspects of it, Alvarez said. “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 study has been accepted for publication in the journal Astronomy & Astrophysics.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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