A detailed image of a stellar nursery illuminated by ultraviolet light from massive young stars shows how intense radiation heats and shapes the fuel for star formation.
This UV-irradiated zone, known as the photodissociation region (PDR), is within the Orion Bar region of the Orion Nebula, which is at the center of “Orion’s Sword,” which hangs from Orion’s Belt.
Although this nebula — a dense cloud of cold gas that is home to intense star formation — appears like a single star to the unaided eye, its true nature as a glowing stellar chamber becomes clear when viewed through a telescope.
Related: The Hubble Space Telescope paints stellar outflows in a new portrait of the Orion Nebula
This image shows the zone’s young, massive stars bombarding and shaping the nebula and its cold gas — the fuel for star formation — with ultraviolet radiation.
Because it is the closest massive region to Earth with intense star formation, astronomers consider studying the Orion Nebula an important tool in developing an understanding of the circumstances surrounding the birth of our solar system.
Viewing the PDR while it’s being heated by starlight could help understand the effect of large amounts of ultraviolet light emitted by young stars on the physics and chemistry of their local environment, as well as the shape and structure of the gas clouds in which they reside are born to understand better.
“These regions are important because they allow us to understand how young stars affect the cloud of gas and dust in which they are born, particularly in locations where stars like the Sun form,” said astrophysicist Emilie Habart of the University of Paris-Saclay in a Expression. (opens in new tab) “Observing photodissociation regions is like looking into our past.”
Exploring the PDR of Orion’s belt serves as a roadmap for further investigations with the James Webb Space Telescope (JWST) as part of the so-called PDRs4All program.
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To create this new highly detailed image, the astronomers on the PDRs4All team examined this region using the second-generation near-infrared camera (NIRC2) in combination with the Keck II telescope’s adaptive optics system. Both instruments are located at the WM-Keck Observatory on the Maunakea volcano on the island of Hawaii.
In the image it is possible to identify in unprecedented detail the various substructures that make up Orion’s Bar. These include ridges, globules and gas filaments, and disks around young stars formed as starlight shapes the nebula’s gas and dust, known as ‘proplyds’.
“Never before have we been able to observe on a small scale how interstellar matter structures depend on their environment, specifically how planetary systems might form in environments heavily irradiated by massive stars,” Habart said. “This could allow us to better understand the legacy of the interstellar medium in planetary systems, namely our origins.”
The team will be particularly interested in observing in the PDR images where gas transitions from a hot ionized state (one with no electrons) into warm atomic gas and then back into the cold molecular gas that can collapse to form stars.
For Keck Observatory astronomer Carlos Alvarez, one of the most exciting elements of this research is that Keck plays a fundamental role in the JWST era of astronomy.
“It was exciting to be the first to see the sharpest near-infrared images of Orion’s Bar ever recorded, along with my colleagues on the James Webb Space Telescope ‘PDRs4All’ team,” he said in a Expression. (opens in new tab) “[The] JWST will be able to drill 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 insights into the properties of the gas and chemical composition of PDRs, which will help us understand the nature of these fascinating star-studded regions.”
The team’s research has been accepted for publication in the journal Astronomy & Astrophysics and can currently be read as a preprint (opens in new tab) in the arXiv paper repository.
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