Astronomers Discover Most Compact Quadruple Star System Ever

Astronomers have uncovered a remarkable star system known as TIC 120362137, identified as the most tightly packed quadruple star system ever documented. This unique arrangement features an eclipsing binary—two stars that periodically obscure one another—additionally blocking the light from a third star, while a fourth star orbits at a greater distance. The findings, published in the journal Nature on March 5, 2024, shed light on the intricate dynamics of hierarchical star systems.

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), researchers initially sought to locate triple star systems. The discovery began when TESS detected a notable dimming in brightness that lasted approximately 1.5 days, suggesting the presence of at least two stars in close orbit. Further observations revealed a second dimming every 26 days, indicating the involvement of a third star. The researchers quickly realized that the behavior of this celestial object could not be attributed solely to a triple system.

Additional careful analysis unveiled the presence of a fourth star, making this system a rare quadruple configuration. The outermost star has an orbital period of just 1,045.5 days, which is the shortest recorded for a star of its kind in such a compact system. The three inner stars are located within a region comparable in size to the orbit of Mercury around the Sun, while the fourth star orbits at a distance similar to that of Jupiter.

The inner trio consists of more massive and hotter stars compared to the Sun, while the outer companion resembles our solar system’s star. According to Tibor Mitnyan, a researcher at the University of Szeged in Hungary and a co-author of the study, “Stars are generally formed in groups via the collapse of large molecular clouds containing dust and gas. Their formation can lead to various structures like clusters, binaries, triples, and quadruples.”

Understanding Stellar Evolution

The research team employed the unique dynamics of this star system to model its future evolution. In approximately 300 million years, the inner stars are predicted to merge into a single white dwarf, the dense remnant of large stars. Mitnyan explains that “the more massive white dwarf is formed after two mergers from the three inner stars, while the less massive white dwarf is simply formed from the originally fourth, most distant star.”

Following this merger, the two remaining white dwarf stars will continue to orbit each other, completing one revolution in around 44 days. Mitnyan noted the significance of this discovery, stating, “If such a double white dwarf system is found today, observers would likely have no idea that it might have originated from such an exotic compact 3+1 quadruple system with an outer period of about a thousand days.”

This research enhances the understanding of star formation and the complexities inherent in multi-star systems. The findings contribute to ongoing investigations into the ways stars interact and evolve over time, posing new questions about the nature of stellar dynamics. As astronomers continue to study such rare systems, they hope to gain deeper insights into the universe’s intricate and often chaotic structures.