The European Southern Observatory has spoilt us again with the release of an incredibly detailed 220-megapixel view of the famous Orion Nebula, one of the closest stellar nurseries to Earth. The newly-released image surprised astronomers by revealing the existence of three separate populations of stars with different ages – a revelation that may force astronomers to rethink their current approach to the formation of star clusters.
Everybody loves Orion. It's always a friendly sight in the winter night sky (from the northern hemisphere at least), and unlike other constellations that will go unnamed, it actually bears a resemblance to its name, Orion - the hunter. Not to mention the fact that the little points of light that make up the join-the-dots figure are awesome in their own right.
Arguably the most famous of these points of light is a red supergiant named Betelgeuse, which holds a morbid fascination for many, owing to the fact that is nearing the end of its days, and will mark its death with a spectacular supernova that will be easily visible from Earth.
But anybody worth their salt knows that the most breath-taking views to be found in the constellation are nestled below the hunter's "belt." We're speaking of course about the Orion Nebula, an enormous star forming region some 1,350 light-years from Earth, that is visible to the naked eye as a milky, smudge on a clear night.
The new shot of the Orion Nebula was captured by the OmegaCAM instrument mounted on ESO's VLT Survey Telescope, located at the Paranal Observatory, Chile. A zoomable version of the release is available on the ESO website.
The image captures the true beauty of the Orion Nebula – a swirling maelstrom of gas and choking dust clouds illuminated by the stars that can be seen dotting about the vista. Many of these stellar bodies belong to a collection of stars known as the Orion Nebula Cluster.
But, when it comes to astronomy, a picture is never simply a picture, but rather an opportunity to better understand the cosmos we inhabit. This particular image of the Orion nebula has given rise to a discovery that could encourage scientists to re-examine their understanding of star clusters.
Image of the Orion Nebula overlayed with the locations of the 3 star populations. The youngest are denoted by red crosses, green are intermediate, while blue represent the oldest stellar bodies (Credit: ESO/G. Beccari)
Following an analysis of the OmegaCAM data, a team of astronomers discovered three populations of stars with differing ages. The observation ran counter to the scientific consensus regarding the formation of the Orion Nebula Cluster, which asserted that the stars comprising the cluster were created in a single, extended "burst" event, that took place some 3 million years ago.
The fact that the three stellar populations were mixed together is one of the reasons that they have eluded detection up to this point.
Speaking to New Atlas, Giacomo Beccari, lead author of the paper detailing the discovery, stated, "As you can see, the populations are fully mixed together. This fact made them difficult to be identified by any previous study. The exquisite photometric quality achieved with OmegaCAM allowed us to unveil the presence of three populations."
The team behind the study had considered that the colors and brightness of the unexpected stars could have resulted from the presence of binary star systems, rather than denoting separate generations of stellar bodies. The companion star in a binary system could be effectively hidden by the larger primary star, rendering it undetectable to current instruments, including OmegaCAM, while giving the duo the appearance of a single large red stellar body.
Whilst Beccari stresses that the team cannot be certain that the stars are not binary systems, he notes that there are several pieces of observational evidence suggesting that the three newly discovered stellar populations share genuine disparities in age.
"What we see with these new data is that the formation history is quite different: the stars in the Orion Nebula Cluster did not form out of a single and extended burst, but three bursts lasting less than 1 million years each" summarized Beccari. "If confirmed, this is a fact that calls for a revision of our understanding of the physics behind the formation of stars in star clusters."
Visit the gallery for more striking views of the Orion Nebula. You can also see a "zoom-in" on the nebula, in the video below.
The paper presenting the findings is available online in the journal Astronomy & Astrophysics.