Rare Quadruple Star System Discovered in the Milky Way

Why in the News?

1. Scientists have discovered an extremely rare quadruple star system in the Milky Way, named UPM J1040−3551 AabBab.
2. The system consists of two cold brown dwarfs orbiting two young red dwarf stars, a configuration that has never been observed before.
3. The discovery provides a new opportunity to study brown dwarfs, which are difficult to detect and understand, and to gain insights into star and planet formation.

Key Highlights

1. Structure of the Quadruple Star System
   1. The system consists of four celestial bodies: two young red dwarf stars and two cold brown dwarfs.
   2. The brown dwarfs orbit the pair of red dwarfs, forming a hierarchical quadruple system.
   3. This is the first known quadruple system with this configuration in the Milky Way.
2. Details about Brown Dwarfs
   1. Brown dwarfs are often referred to as “failed stars” because they lack sufficient mass to sustain hydrogen fusion like normal stars.
   2. They form from collapsing gas and dust clouds, similar to stars, and can be up to 70 times more massive than Jupiter.
   3. Their atmospheres can resemble gas giant planets, containing molecules like H2O and cloud formations.
3. Difficulty in Detecting Brown Dwarfs
   1. Brown dwarfs are cold and faint, emitting very little visible light.
   2. They are often detected when they orbit brighter companion stars, which allows astronomers to infer their properties.
   3. Studying such systems helps determine the age, temperature, and composition of the brown dwarfs indirectly.
4. Significance of the Discovery
   1. Unlike most low-mass stars and brown dwarfs, which are usually single, this system shows that a brown dwarf can have a companion, which occurs in less than 5% of cases.
   2. The brighter red dwarfs provide a reference point to measure and study the faint brown dwarfs more accurately.
   3. The discovery adds to our understanding of multiple-star systems, which differ significantly from single stars like the Sun.
5. Research and Collaboration
   1. The study was led by Professor Zenghua Zhang from Nanjing University.
   2. Collaborating institutions included the University of Hertfordshire (UK), Brazilian National Astrophysics Laboratory, SOAR Telescope (Chile), and Center for Astrobiology (Spain).
   3. The research was published in the Monthly Notices of the Royal Astronomical Society in September 2025.

Implications

1. Advancing Knowledge of Brown Dwarfs
   1. Enables better detection and characterization of faint brown dwarfs.
   2. Helps astronomers estimate age, composition, and temperature
2. Understanding Star Formation
   1. Shows rare configurations in star systems, challenging existing models.
   2. Provides clues about how low-mass stars and substellar objects form in multiple systems.
3. Insights into Planet Formation
   1. Brown dwarfs act as a bridge between stars and giant planets, offering insights into planetary atmospheres and evolution.
   2. Studying their formation environment can reveal conditions necessary for planet formation.
4. Contribution to Dark Matter Studies
   1. Brown dwarfs represent undetectable mass in the universe.
   2. Their abundance and distribution help refine estimates of mass distribution in the Milky Way.
5. Enhancing Astronomical Techniques
   1. Demonstrates the importance of multi-institution collaboration and advanced telescopes like SOAR.
   2. Sets a benchmark for studying faint substellar objects in multiple-star systems.

Challenges and Way Forward

Conclusion

The discovery of the UPM J1040−3551 AabBab quadruple system is a milestone in astronomy as it provides a rare opportunity to study brown dwarfs and low-mass stars in a single system. It enhances our understanding of star and planet formation, while also helping refine the distribution of mass in the universe. With further observations and improved technology, such discoveries could significantly expand knowledge of rare celestial configurations and the mysteries of the Milky Way.