An international team led by Juan Diego Soler of the University of Vienna used two of the world’s most powerful radio telescopes to uncover previously hidden structures in the Orion Nebula. As part of this project, the team created the most detailed maps of neutral hydrogen ever compiled for this region of massive star formation.
Giant hydrogen clouds in the Orion Nebula
The findings shed light on the complex interactions between star-forming regions and their surroundings and suggest that the Orion Nebula formed as a result of numerous episodes of stellar feedback, rather than through the formation of a single expanding bubble. This is reported by the website phys.org
The Orion Nebula is one of the most famous objects in the night sky. It can be seen even with the naked eye; it has been studied for centuries and observed using nearly all modern astronomical instruments. However, astronomers have recently discovered that one of its most important components had remained virtually invisible until now.
Using some of the world’s most powerful radio telescopes, an international team led by Soler of the University of Vienna has created the sharpest maps of neutral atomic hydrogen in the Orion Nebula ever produced. The observations revealed giant expanding shells, previously undetected voids, and mysterious elongated structures surrounding the region closest to Earth where massive stars are forming.
Hydrogen is the most abundant element in the universe. In its neutral atomic form, it emits faint radio waves with a wavelength of 21 centimeters (8.3 inches), allowing astronomers to detect interstellar gas that would otherwise be invisible. To detect this radiation with unprecedented detail, researchers combined observational data from the Karl G. Jansky Very Large Array (VLA) in the United States and the 500-meter-aperture Spherical Radio Telescope (FAST) in China.
The Complex Structure of the Envelope
Previous studies indicated that the envelope surrounding the Orion Nebula contains a mass approximately 1,000 times that of the Sun. New observations of hydrogen point to a mass that is nearly 10 times smaller. “Measuring mass is fundamental,” Soler says, “because it tells us about the efficiency of these newly formed stars shaping their environment with wind and radiation.”
The new maps also reveal what appears to be a second expanding cavity within the main shell, as well as an elongated “bulge” of atomic gas extending approximately four light-years outward from the bubble. These structures suggest that the Orion Nebula formed as a result of numerous episodes of stellar feedback, rather than from a single expanding bubble.
A Review of Star Formation Processes
The complexity revealed by these observations calls into question our current understanding of star formation, explains Daniel Seifried, a co-author of the paper and a researcher at the University of Cologne. “These stunning observations serve as a reference for many modern astrophysical simulations investigating the evolution of gas and stars in the Milky Way. These are the kind of images that challenge the theoretical models and numerical simulations that we use to understand how massive stars affect their immediate surroundings.”
Astronomers’ research demonstrates the capabilities of the latest generation of radio telescopes in revealing new pieces of the star-formation puzzle.
Researchers say that Orion is just the beginning. Recently developed methods show how future interferometers will reveal the hidden structure and dynamics of the interstellar medium—even in regions that astronomers thought they already understood well.
