Astronomers have considered the “sword” of Orion

(ORDO NEWS) — Astronomers using the W.M. Keka on the island of Hawaii, obtained from Mauna Kea the most detailed and complete images of the zone where the famous constellation of Orion is exposed to ultraviolet radiation from massive young stars.

This irradiated neutral zone, called the photodissociation region (PDR), is located in the Orion Nebula, an active star-forming site located in the middle of the “sword” dangling from Orion’s “belt”.

When viewed with the naked eye, the nebula is often mistaken for one of the constellation’s stars, and when viewed through a telescope, the nebula is visible as a glowing, gaseous “stellar nursery” located 1,350 light-years from Earth.

Since the Orion Nebula is our closest region of massive star formation, and may be similar to the environment in which our solar system was born, studying its PDR is an ideal place to look for information about how stars and planets are created.

“Observing regions of photodissociation is like looking into our past,” said Emily Khabar, associate professor at the Institute of Astrophysics at the University of Paris-Saclay and lead author of a paper on the study.

“These regions are important because they allow us to understand how young stars affect the gas and dust cloud in which they are born.”

The study has been accepted for publication in the journal Astronomy & Astrophysics, and is available in preprint format at

To investigate Orion’s PDR, the PDRs4All team used the Keck Observatory’s Second Generation Near Infrared Camera (NIRC2) in conjunction with the Keck II telescope’s adaptive optical system.

They provided an image of the area in such extreme detail that the researchers were able to make out the substructures of the Orion bar: ridges, filaments, globules, and proplids.

New images of the Orion Bar from the Keck Observatory will help astronomers gain a deeper understanding of star formation as they show in detail where hot ionized gas is converted into warm atomic and cold molecular gases in the PDR. Mapping this change is important because dense, cold molecular gas is the fuel needed to form stars.

These new studies from the Keck Observatory will form the basis for planning future James Webb telescope observations of the Orion Bar.


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