Is this star “eating” a brown dwarf? MIT-led astronomers catch a rare cosmic feeding 300 light-years away
Astronomers have spotted a strange interaction between two low-mass objects about 300 light-years from Earth. A small red dwarf star appears to be slowly pulling material from a nearby brown dwarf, creating a long-lasting cosmic feeding process.
The system, named ZTF J0440+2325, offers a rare look at how stars and planet-like objects can interact when they orbit extremely close to each other.
A star and brown dwarf locked in a close orbit
The system contains a low-mass red dwarf and a brown dwarf. The two objects orbit each other every 86.65 minutes, with their entire orbit small enough to fit within the diameter of the Sun.
The red dwarf is about 85 times as massive as Jupiter, while the brown dwarf has a mass around 25 times that of Jupiter.
The star is slowly stealing material
The brown dwarf is so close to the red dwarf that material is being pulled away from it. This process is known as accretion. The stripped material forms a stream that falls directly onto the surface of the red dwarf at very high speeds.
Scientists say this is the first observed case of a low-mass star actively accreting material from another low-mass object.
How much is the brown dwarf losing?
Researchers estimate that the brown dwarf is losing material at a rate of around one hundred-thousandth of Earth’s mass every year. Although that sounds enormous, it represents only a small fraction of the brown dwarf’s total mass. The slow rate means the process could continue for hundreds of thousands or even billions of years.
A mysterious triangular signal
The system was first noticed in observations from the Zwicky Transient Facility. Astronomers spotted an unusual repeating pattern in its brightness that looked like a triangle.
Follow-up observations showed that the system was not a typical “black widow” binary. Instead, the unusual signal came from the interaction between the red dwarf and its brown dwarf companion.
Why does the system glow?
As material from the brown dwarf strikes the red dwarf, it creates an extremely hot region on the star’s surface. As the objects orbit, this hot spot moves in and out of view. This produces the distinctive triangular changes in brightness that initially caught astronomers’ attention.
The discovery gives scientists a new example of how a star can consume a companion gradually rather than swallowing it whole.
