Astronomers using a telescope atop Maunakea on the Big Island have captured the most detailed and complete images ever taken of the zone where the constellation of Orion gets zapped with ultraviolet radiation from massive young stars.
“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,” Emilie Habart, an Institut d’Astrophysique Spatiale associate professor at Paris-Saclay University and lead author of a paper on the discover, said in a press release. “This may allow us to better understand the heritage of the interstellar medium in planetary systems, namely our origins.”
Massive young stars emit large quantities of UV radiation that affect the physics and chemistry of their environment; how this surge of energy impacts and shapes star formation is not yet well known. The new Keck Observatory images will help deepen astronomers’ understanding of this process because they reveal in detail where gas in Orion’s photo-dissociation region changes from hot ionized gas to warm atomic and finally to cold molecular gas.
Mapping this conversion is important because the dense, cold molecular gas is the fuel needed for star formation.
“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,” Carlos Alvarez, a staff astronomer at Keck Observatory and co-author of the study, said in the press release.
To probe Orion’s photo-dissociation region, an irradiated neutral zone located in the Orion Bar within the Orion Nebula, an active star-forming site found in the middle of the “sword” hanging from Orion’s “belt,” the team of astronomers used the W. M. Keck Observatory’s second generation near-infrared camera in combination with the Keck II telescope’s adaptive optics system. They successfully imaged the region with such extreme detail that the researchers were able to spatially resolve and distinguish the Orion Bar’s different substructures formed as starlight blasted and sculpted the nebula’s mixture of gas and dust.
When viewed with the naked eye, the Orion Nebula is often mistaken for one of the stars in the constellation; when viewed with a telescope, it is seen as a glowing gaseous stellar nursery located 1,350 light-years from Earth. Its photo-dissociation region is an ideal place to find clues as to how stars and planets are created.
“Observing photo-dissociation regions is like looking into our past,” Habart said in the press release. “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 study has been accepted for publication in the journal Astronomy and Astrophysics, and is available in preprint format by clicking here. (arXiv.org)
These pathfinder observations also have assisted in the planning of the James Webb Space Telescope Early Release Science program PDRs4All: Radiative feedback of massive stars and informed plans for Webb telescope observations of the Orion Bar.
“One of the most exciting aspects of this work is seeing Keck play a fundamental role in the (James Webb Space Telescope) era,” Alvarez said in the release. “(The James Webb Space Telescope) will be able to dive deeper into the Orion Bar and other (photo-dissociation regions), and Keck will be instrumental in validating (the James Webb Space Telescope’s) early science results. Together, the two telescopes can provide unique insight into the characteristics of the gas and chemical composition of (photo-dissociation regions), which will help us understand the nature of these fascinating star-blasted regions.”