WEAVE discovers a mysterious iron bar in the Ring Nebula

16 January 2026

Composite RGB image of the Ring Nebula from WEAVE/LIFU emission-line images showing the iron bar structure
Colour image of the Ring Nebula made from four WEAVE/LIFU emission-line images. The bright outer ring is light from oxygen ions, and the bar in the middle is plasma of iron that has lost four electrons. The image covers 120 × 110 arcseconds. Credit: University College London / ING.

A team from University College London and Cardiff University has found a bar-shaped cloud of iron inside the Ring Nebula (Messier 57, NGC 6720) that nobody had seen before. They used WEAVE, the new spectrograph on the William Herschel Telescope on La Palma, and have published the result in Monthly Notices of the Royal Astronomical Society.

The bar lies inside the inner elliptical layer of the nebula and is about 500 times as long as Pluto's orbit around the Sun. The iron in it is thought to weigh about as much as the planet Mars. The Ring Nebula, first recorded by Charles Messier in 1779, is made of material thrown off by a dying star, which is what will happen to our own Sun in several billion years.

A new look at a familiar object

The researchers used WEAVE's Large Integral Field Unit (LIFU), a bundle of hundreds of optical fibres that records spectra across the whole nebula at once, at every optical wavelength. This made it possible to map what the nebula is made of in more detail than any other observatory had managed.

Eight individual WEAVE LIFU emission-line images of the Ring Nebula showing different ionic species
Eight separate WEAVE LIFU emission-line images. Top row: [Fe V] 4227 Å (iron that has lost four electrons), [O I] 6300 Å, [O II] 3727 Å and [O III] 4959 Å. The iron bar only shows up in the [Fe V] image. Credit: University College London / ING.

"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."

Dr Roger Wesson, University College London / Cardiff University

Where the iron came from is still unclear

There are two main ideas. The bar may tell us something new about how the star threw off its outer layers, or it may be a stretched arc of plasma from a rocky planet that was vaporised as the dying star expanded. Professor Janet Drew (UCL) said: "We definitely need to know more, particularly whether any other chemical elements co-exist with the newly-detected iron."

Professor Scott Trager (University of Groningen), WEAVE Project Scientist, 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."

Dr Wesson said: "It would be very surprising if the iron bar in the Ring is unique." The team plans to observe the nebula again at higher spectral resolution, and expects to find similar structures in other planetary nebulae as the WEAVE survey goes on.

Reference: Wesson, R. et al. (2026), "WEAVE imaging spectroscopy of NGC 6720: an iron bar in the Ring", MNRAS, doi:10.1093/mnras/staf2139.

Source: ING press release, 16 January 2026, Isaac Newton Group of Telescopes