A team of European astronomers has discovered an impressive bar-shaped iron cloud within the famous Ring Nebula, providing an unexpected glimpse into the inner workings of this celestial spectacle.
The discovery, led by researchers from Cardiff University and University College London (UCL), is the first time such structures have been observed within a nebula.
This newly discovered feature appears as a thin band of perfectly aligned iron atoms inside the inner layer of the nebula’s elliptical shell.
Its huge scale is astonishing. This bar extends approximately 500 times the distance from the Sun to Pluto, and its total iron mass is comparable to Mars.
Ring Nebula: An Astronomical Classic
First observed by French astronomer Charles Messier in 1779, the Ring Nebula is located in the northern constellation Lyra.
It is a luminous shell of gas ejected by a star nearing the end of its life, a fate that our Sun will share in billions of years.
For centuries, the nebula has been photographed extensively, including through the infrared lens of the James Webb Space Telescope, but the iron bar has remained hidden until now.
History of discovery
This breakthrough was made possible by a new instrument, the WHT Enhanced Area Velocity Explorer (WEAVE), installed on the Isaac Newton Group’s 4.2-meter-diameter William Herschel Telescope.
Astronomers used WEAVE’s Large Integral Field Unit (LIFU) mode to obtain spectra across all optical wavelengths at every point in the nebula.
This unprecedented spectral mapping allowed the research team to visualize in detail the chemical composition of the Ring Nebula for the first time.
Lead author and astronomer Dr Roger Wesson from UCL and Cardiff University explained that although the nebula has been extensively studied with a number of telescopes, WEAVE provided a completely new perspective.
“WEAVE allows us to look in new ways and get much more detailed information than before.
“By continuously acquiring spectra across the nebula, we can image the nebula at any wavelength and determine its chemical composition at any location,” he said.
The origin of the iron rod remains a mystery
Despite the excitement of the discovery, the formation of iron bars remains uncertain.
Researchers are considering two main hypotheses. For one, the bar could indicate an unusual pattern in the way the parent star expels its outer layers, or it could be the result of evaporated material from a rocky planet that was engulfed by the star during expansion.
Co-author Professor Janet Drew from UCL stressed that further analysis was needed. Determining whether other chemical elements are related to iron could provide important clues about the origins of the bars and help refine theoretical models.
Next steps to understanding the Ring Nebula
The research team is preparing follow-up observations using WEAVE’s LIFU with higher spectral resolution to examine the iron bars in more detail.
These studies aim to elucidate the process that forms this mysterious feature and investigate whether similar structures exist in other nebulae.
WEAVE is currently conducting eight large-scale surveys over five years, ranging from nearby white dwarfs to distant galaxies.
Professor Drew’s research in stellar, circumstellar, and interstellar physics focuses on investigating ionizing nebulae in the northern Milky Way.
Wesson suggested that findings like the iron bars may not be unique to ring nebulae, and that further observations could reveal more such phenomena.
As astronomers continue to map the Ring Nebula and other stellar debris in unprecedented detail, this discovery opens a new window into the complex processes governing the life and death of stars, and the unexpected treasures they leave behind.
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