European researchers have discovered a strange bar-shaped cloud of iron within the Ring Nebula, which they believe may be the remains of a vaporized planet.
Astronomers from University College London and Cardiff University led the new research, which was reported in a recent paper in the Monthly Notices of the Royal Astronomical Society, revealing the discovery of an unusual iron cloud using new high-resolution data.
French astronomer Charles Messier first discovered the Ring Nebula in 1779, between the stars Beta and Gamma Lyrae. Although too faint to be seen with the naked eye, the nebula is readily visible through a telescope, with the first photograph of it taken by Eugene von Gothard in 1886.
Among the northern constellation Lyra, Messier spotted the colorful shell of burning gas produced as the star M57 closed out its nuclear fuel-burning phase. We can expect similar behavior from the Sun, but only billions of years from now.
The bar of iron atoms sits inside the ellipse-shaped Ring Nebula’s inner layer. The atoms have a mass comparable to that of Mars but are distributed over an area about 500 times the size of Pluto’s orbit.
Viewing the Ring Nebula
The recent data was obtained by observations made with the Isaac Newton Group’s 4.2-meter William Herschel Telescope, located in the Canary Islands. To do so, researchers employed the WHT Enhanced Area Velocity Explorer’s (WEAVE) Large Integral Field Unit (LIFU) mode. LIFU consists of hundreds of optical fibers, allowing researchers to collect spectra across the entire Ring Nebula in all wavelengths. Never before has such an observation been possible, enabling researchers to discover the iron cloud.
“Even though the Ring Nebula has been studied using many different telescopes and instruments, WEAVE has allowed us to observe it in a new way, providing so much more detail than before,” said lead author Dr Roger Wesson, based jointly at UCL’s Department of Physics & Astronomy and Cardiff University. “By obtaining a spectrum continuously across the whole nebula, we can create images of the nebula at any wavelength and determine its chemical composition at any position.”
“When we processed the data and scrolled through the images, one thing popped out as clear as anything – this previously unknown ‘bar’ of ionised iron atoms, in the middle of the familiar and iconic ring,” he continued.
A Possible Vaporized Planet
How the iron cloud formed remains uncertain, but the team has some hypotheses. One possibility is that the parent star’s ongoing expulsion of the Ring Nebula may have produced the mysterious cloud of atoms. The other possibility is that the iron may be the remains of a vaporized planet, forming a plasma arc after being destroyed in the stellar expansion. Further observations will be necessary to determine whether either scenario is true.
“We definitely need to know more—particularly whether any other chemical elements co-exist with the newly-detected iron, as this would probably tell us the right class of model to pursue,” said co-author Professor Janet Drew, also based at UCL Physics & Astronomy. “Right now, we are missing this important information.”
Continuing to Explore the Ring Nebula
The team’s efforts to push WEAVE’s LIFU even further are already underway, with plans for a follow-up study. In their next round of observations, the team hopes that higher-resolution images will provide additional clues to the formation of the iron cloud. That study will not be the only one to use the instrument; WEAVE is already scheduled to conduct 8 surveys over the next five years, targeting objects ranging from distant galaxies to relatively close white dwarf stars.
“It would be very surprising if the iron bar in the Ring is unique. So hopefully, as we observe and analyse more nebulae created in the same way, we will discover more examples of this phenomenon, which will help us to understand where the iron comes from,” Dr Wesson added.
“The discovery of this fascinating, previously unknown structure in a night-sky jewel, beloved by sky watchers across the Northern Hemisphere, demonstrates the amazing capabilities of WEAVE,” commented Professor Scott Trager, WEAVE Project Scientist based at the University of Groningen. “We look forward to many more discoveries from this new instrument.”
The paper, “WEAVE Imaging Spectroscopy of NGC 6720: An Iron Bar in the Ring,” appeared in Monthly Notices of the Royal Astronomical Society on January 15, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.