14.08.2026
With a lens array in Chile, astronomers capture clumps of gas from a dying star returning to the Galaxy
Wispy arcs of gas (red) detected by MOTHRA surround the Helix nebula (pink, yellow, and blue), as seen by the Hubble Space Telescope and the Nicholas U. Mayall Telescope.ANDREW MCCARTHY
A novel telescope still under construction in Chile has captured one of astronomy’s missing links: clumps of gas cast off by a dying star and recycled into the Galaxy. The observations reveal how carbon, oxygen, and other elements forged inside stars become part of the raw material for future stars, planets—and ultimately life.
As reported this week in Nature, the discovery came almost by accident during test observations in November 2025, as astronomers were building a telescope that combines hundreds of high-end, off-the-shelf telephoto lenses into a single compound eye. With fewer than 200 of the telescope’s planned 1140 lenses installed, the researchers pointed the instrument at the Helix nebula, a bright ring of gas about 650 light-years from Earth that formed as a Sun-like star shed its outer layers at the end of its life. Astronomers have long assumed this kind of expelled material mixes with the thin gas between stars and helps form new generations of stars and planets. But catching that process in action has proved difficult.
Even in its unfinished state, the telescope revealed 22 faintly glowing arcs beyond the bright ring of the nebula, in a region known as its halo. The team interprets the arcs as bow shocks—similar in shape to the waves in front of a boat—created as the clumps of ejected gas plow through interstellar gas. The farther the bow shocks lie from the nebula’s center, the smaller, fuzzier, and more fragmented they become—a sign of the gases mixing. Because those clumps have been traveling longer, the pattern suggests they are gradually eroding and dissolving into surrounding gas, a process thought to take about 10,000 years.
“The details of the halo shown in the image are impressive,” says astronomer Sun Kwok of the University of British Columbia, who was not involved in the new work. Although some large bow shocks have previously been seen around the Helix nebula, he says, “These new observations give us insights into the interaction between stellar mass loss and the interstellar medium.”
The images were taken by the Modular Optical Telephoto Hyperspectral Robotic Array, or MOTHRA, at El Sauce Observatory in Chile. Built for a few tens of millions of dollars with support from Alex Gerko, founder and CEO of XTX Markets, MOTHRA is expected to be complete by the end of the year. Like its forerunner, Dragonfly, a lens array in New Mexico, MOTHRA’s primary goal is to map the tendrils of gas that thread between galaxies. “Most atoms are not in stars,” says project co-leader Roberto Abraham of the University of Toronto. Instead, they lie within the tenuous “cosmic web” between galaxies, where gas is so thin that it emits only a trickle of light.
The team chose the Helix nebula because it is large, bright, and one of the best studied nebulae in the sky, says project co-leader Pieter van Dokkum of Yale University. But the newly discovered structures are much fainter than the nebula’s familiar bright ring—precisely the sort of dim emission MOTHRA was designed to detect. “And lo and behold we saw all this new stuff,” Van Dokkum says. “It was unbelievably exciting.”
“Although planetary nebulae have been subjects of intense studies for over 200 years, there still remain many unsolved problems,” Kwok adds. “Just because an object is bright and has been well observed, we cannot assume that we know everything about the object. See what a low-cost telescope can do!”
Quelle: AAAS