Astronomers have made an amazing discovery, finding a binary system with an incredibly tight rotation that allows both objects to fit comfortably inside the Sun. This system, known as ZTF J2020+5033, is located just 457 light-years away and consists of a high-mass brown dwarf and a low-mass red dwarf that orbit each other with a dizzying cycle of 1.9 hours. The distance between the two objects is less than half the radius of the Sun, making it the closest orbit the brown dwarf has had so far.
The discovery, led by astrophysicist Karim El-Badri of the Harvard-Smithsonian Center for Astrophysics, sheds light on the rare phenomenon of brown dwarfs being in close double bonds with other small stars. The discovery of ZTF J2020+5033 could provide valuable insights into the formation and evolution of these enigmatic objects.
Brown dwarfs are unique celestial bodies that fall between the classification of stars and planets. They are not massive enough to support hydrogen fusion like stars, but can ignite deuterium in their cores. Brown dwarfs, which range from 13 to 80 times the mass of Jupiter, are difficult to detect because of their small size and dimness. Of the approximately 5,000 known brown dwarfs in the Milky Way, only about 1% occur in twins with stars similar to the Sun or smaller in mass within a few astronomical units.
The search for double stars with brown dwarfs is of great interest to astronomers because it provides an opportunity to study their properties and better understand their origin. El-Badri and collaborators used the Zwicky Transient Facility to search for low-mass double stars that could potentially include a brown dwarf, leading to the discovery of ZTF J2020+5033. Further analysis using various data sets, including Gaia data, allowed precise measurements of the system and confirmed its characteristics.
The red dwarf in the ZTF J2020+5033 system is relatively small: it has only 17.6% of the radius and 13.4% of the mass of the Sun. On the other hand, the brown dwarf is at the upper mass limit for such objects: its mass is about 80.1 times the mass of Jupiter, and its radius is comparable to that of Jupiter.
Another intriguing aspect of this discovery is the age of both objects. Researchers believe that the brown and red dwarfs were once much larger than their current sizes, suggesting that they were once at least five times farther apart. The process of “magnetic braking,” where matter flying out of a star is slowed by its magnetic field, appears to be an effective mechanism for reducing the orbit of double stars. This phenomenon is observed even in low-mass stars and brown dwarfs, which is confirmed by the narrow orbit in the system ZTF J2020+5033.
This groundbreaking discovery opens new possibilities for studying binary systems involving brown dwarfs and provides valuable insights into their formation and evolution. Scientists continue to explore the mysteries of the Universe, and discoveries like ZTF J2020+5033 contribute to our understanding of celestial objects and their complex relationships.