Astronomers have discovered a star slowly eating its companion in an extraordinary cosmic feast that could last billions of years.
A small star about 300 light-years from Earth is feeding on a companion that circles it every 87 minutes. The two objects are remarkably close, yet the star is drawing away material slowly enough that the feeding could continue for hundreds of thousands or even billions of years.
The pair, named ZTF J0440+2325, lies within the Milky Way. Its smaller member is a brown dwarf, a planetlike object that falls between planets and stars in mass. The brown dwarf has about 25 times Jupiter’s mass, while the star has about 85 times Jupiter’s mass. Both are small by stellar standards, and the brown dwarf’s entire orbit could fit within the Sun’s diameter.
Most planets occupy stable orbits that keep them apart from their stars. Astronomers have observed plenty of these systems, along with a handful of stars rapidly engulfing planets that come too close. The new discovery reveals another possibility. Reported by scientists at MIT and other institutions in an October 5, 2026, paper in Nature Astronomy, it represents the first observation of a low-mass star slowly and steadily consuming material from another low-mass object.
A repeating triangle in the light curve
Several years ago, Kevin Burdge, an assistant professor of physics at MIT, noticed an unusual brightness pattern while reviewing data from the Zwicky Transient Facility, or ZTF. The facility uses a camera on a telescope at California’s Palomar Observatory to scan for rapid brightness changes that could signal a supernova, a gamma-ray burst, or colliding neutron stars. A supernova’s light curve, a record of brightness over time, resembles a bell as the exploding star brightens and then fades. The light curve that caught Burdge’s attention instead showed a repeating triangular pattern.
“I remember first looking at this and thinking, stars don’t make triangular waveforms like this,” he recalls.
At the time, Burdge and his colleagues were investigating a different signal, which they identified as a “black widow binary.” In that kind of system, an extremely dense, spinning neutron star slowly consumes a much smaller companion star, behavior that evokes its spider namesake. Burdge wondered whether the triangular signal came from another black widow. In those systems, however, the light shows a pronounced wobble as the lightweight companion whips around the much heavier neutron star.
“We weren’t seeing that whipping back and forth here,” Burdge says. “It didn’t make any sense. We couldn’t explain what this was.”
The wobble rules out a neutron star
Recently, Burdge returned to the unexplained signal with Aaron Householder, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. They wanted to test an idea Burdge and his colleagues had considered years earlier.
“If you have less mass in the system overall, things can gently orbit each other without whipping back and forth,” Burdge says. “That was the idea. But we never had any proof. And this weird triangle just sat for years.”
Using the original ZTF signal to locate the source, the researchers directed multiple telescopes toward it. They measured several properties, including a small but detectable wobble, and compared the motion with that of black widows and similar binary systems.
“That was the real clincher for this system,” Householder says. “When we measured that wobble, we found we were not seeing a black widow. This was a low-mass star that’s orbited by a brown dwarf. The wobble was too small in amplitude to be anything else.”
Matter crashes directly onto the star
With the objects’ masses and tight orbit established, the team investigated whether one could be pulling material from the other. This process, called accretion, is most often observed around compact objects such as black holes and neutron stars, which pack enormous mass into a small space. When a black hole draws matter from a much smaller nearby object, the material gathers around it in a disk.
“The difference here is, the thing absorbing matter is not a tiny black hole but a star, which is relatively big in size,” Burdge explains. “So matter just pummels directly onto the surface, at very high speeds, like an asteroid hitting the moon.”
The researchers tested that possibility with simulations based on the properties of the star and brown dwarf. They modeled particles of matter on the brown dwarf and used the laws of physics and equations of motion to track where those particles would travel over time.
“When we track those test particles, we see they indeed fall right onto the surface of the star,” Householder says. “This is the first time we’ve caught a low-mass star actively accreting from another low-mass object.”
The team then considered how the steady stream would appear from a distance as the brown dwarf and its flowing material circled the star.
“It’s like you’ve got this continuous fireball onto one of the objects, and as one orbits the other, that hotspot comes in and out of view, and the peak of the triangle signal is when you’re looking right at the fireball,” Burdge explains.
Slow feeding could last billions of years
The researchers calculated that the brown dwarf must be supplying about 1/100,000 of Earth’s mass in material each year. To convey the scale, they compared the flow to about 40 million dump trucks’ worth of material, or roughly 1.3 trillion one-pound burritos every second. Even that enormous quantity represents only a small fraction of the brown dwarf’s mass, making the estimated transfer slow and steady relative to the available supply.
“When we think of stars interacting with planets or brown dwarfs, the picture is always that the star eventually swallows the other thing,” says Burdge. “This is what will happen to the Earth when the Sun becomes a red giant. But here, we’ve found an alternative: Instead of swallowing the thing up, the star can gradually eat it, for billions of years.”
Alongside Burdge and Householder, the study’s MIT coauthors include Kaitlyn Shin, Saul Rappaport, Joheen Chakraborty, and Emma Chickles. The collaboration also includes researchers from Caltech, the University of Hawaii, the Instituto de Astrofísica de Canarias and the Universidad de La Laguna in Spain, and the Harvard-Smithsonian Center for Astrophysics.
With an explanation for the triangular light curve, the team hopes to identify other nearby systems where stars gradually draw material from their companions.
“It’s inspiring a lot of new searches on our part,” Householder says. “I think we’re going to learn a lot about a different kind of way that planets and brown dwarfs interact with their host stars.”
Reference: “Stable mass transfer from a substellar object onto an M dwarf” by Aaron Householder, Kaitlyn Shin, Kevin B. Burdge, Thomas R. Marsh, Saul A. Rappaport, Kareem El-Badry, Joheen Chakraborty, Emma Chickles, Fei Dai, Matthew J. Graham, S. R. Kulkarni, Pablo Rodríguez-Gil, Andrew Vanderburg and Samuel Whitebook, 5 October 2026, Nature Astronomy.
DOI: 10.1038/s41550-026-02992-6
This research was supported, in part, by the National Science Foundation.
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