In a groundbreaking development poised to revolutionize our understanding of exoplanetary systems, a team of astronomers from the University of New South Wales (UNSW) Sydney has unveiled the detection of 27 promising circumbinary planet candidates. These planets orbit not one, but two stars—a celestial setup that until now has remained largely elusive to astronomers. Employing a novel technique based on apsidal precession, this new method extends the search for planets beyond the traditional transit detection framework that has dominated exoplanet discoveries to date.
Circumbinary planets occupy a niche sector of planetary science, wherein worlds revolve around a binary star system. Despite the common cultural reference to the fictional Tatooine from Star Wars, the actual known population of such planets has been limited to 18 confirmed discoveries, compared to over 6,000 planets detected orbiting single stars. This disparity largely arises from the biases in detection methodologies that favor planets crossing in front of a single star, causing a detectable dip in starlight as observed from Earth.
The technique harnessed by the UNSW team pivots away from relying solely on planetary transits. Instead, it utilizes detailed observations of apsidal precession—a slow rotation or wobble in the elliptical orbits of binary stars caused by gravitational influences. Over long-duration monitoring, deviations from predictable eclipse timings between binary stars can be discerned. These variations, when unexplained by classical stellar interactions or relativistic effects, strongly suggest the gravitational tug of an unseen third body, potentially a planet, influencing the binary orbits.
Data for this pioneering study were sourced from NASA’s Transiting Exoplanet Survey Satellite (TESS), launched in 2018 with the primary goal of discovering exoplanets. While TESS’s original mission centered on detecting planets via transits, the richness of its photometric dataset allowed researchers to explore apsidal precession signals across nearly 1,600 eclipsing binary systems. The detection of 27 candidates signals an approximate 2% occurrence rate of circumbinary planets within these binaries, greatly enriching our catalog and opening new frontiers for exoplanet research.
The range of planet candidates identified spans a wide spectrum of masses—from Neptune-sized objects to gas giants ten times the mass of Jupiter—positioned at varying astronomical distances from roughly 650 to 18,000 light years from Earth. This distribution across both the Southern and Northern hemispheres means these fascinating systems are observable year-round by astronomers equipped with sufficiently powerful telescopes, promising exciting opportunities for follow-up observations.
What makes these discoveries particularly significant is how they begin to fill a critical knowledge gap in planetary astrophysics. Over half of stars in the Milky Way exist as binaries or in multiple star systems, yet the majority of exoplanet studies have focused on planets orbiting solitary stars like our Sun. By illuminating this largely uncharted population of circumbinary planets, the UNSW study challenges existing paradigms and introduces new questions about planet formation, orbital dynamics, and potential habitability in complex stellar environments.
Confirming these planet candidates, however, requires more than detecting orbital precession signals. The research team has embarked on follow-up spectroscopic studies using the Anglo Australian Telescope, analyzing the light spectra from the host binary stars to rule out the presence of other massive objects such as brown dwarfs, white dwarfs, or even black holes. Only after eliminating these possibilities can the candidates be validated as genuine planets.
Beyond immediate discoveries, this research presents profound implications for the future of exoplanet detection techniques. The demonstrated sensitivity of apsidal precession measurements using TESS data suggests that this method could extend to detecting planets as small as Earth in the near future. By supplementing, and in some cases superseding, transit-based detections, apsidal precession opens a new observational window into planetary systems that do not conveniently align with our line of sight.
This novel methodology also holds unrivaled potential when combined with next-generation astronomical surveys, such as the Legacy Survey of Space and Time (LSST) conducted by the Vera C. Rubin Observatory. The massive datasets expected from LSST over its 10-year mission are likely to amplify discoveries, potentially revealing thousands more circumbinary planets, significantly broadening the census of diverse planetary systems.
Astrophysicists and cosmologists alike are enthusiastic about how these findings challenge the long-held assumption that single-star systems dominate planetary habitats. If circumbinary planets prove to be not only common but also capable of hosting environments conducive to life, this discovery could dramatically expand the horizons of astrobiology and the search for extraterrestrial life, suggesting that life-bearing worlds might be far more ubiquitous than previously imagined.
The personal journey of lead author Ms. Margo Thornton, who led the study as a PhD candidate at UNSW, highlights the human element behind scientific breakthroughs. Her longstanding fascination with the stars and persistent inquiry into celestial phenomena blossomed into this moment of discovery, underscoring the excitement and uniqueness of being among the first to witness signals hinting at otherwise invisible worlds.
Looking ahead, the team’s collaborative efforts span international boundaries, engaging researchers from the United States, United Kingdom, and China to characterize circumbinary systems observable from the Northern Hemisphere. Simultaneously, computational simulations are underway to better understand the formation mechanisms, evolutionary processes, and long-term stability of these orbiting bodies within the gravitational interplay of binary stars.
This pioneering research not only offers a fresh perspective on planet discovery but also heralds a transformative epoch in astrophysics, where the universe’s complexity is gradually unveiled through innovative observational strategies. Ultimately, the realization that real-life “Tatooines” may be more common than fiction inspires profound questions about our cosmic neighborhood and humanity’s place within it, invigorating the timeless quest to comprehend the vast cosmos we inhabit.
Subject of Research: Detection and characterization of circumbinary planets using apsidal precession of eclipsing binary stars
Article Title: Detection of 27 candidate circumbinary planets through apsidal precession of eclipsing binaries observed by TESS
News Publication Date: 4-May-2026
Web References:
- Monthly Notices of the Royal Astronomical Society Article
- NASA TESS Mission
- Anglo Australian Telescope
References: DOI: 10.1093/mnras/stag515
Image Credits: UNSW Media / Richard Freeman
Keywords
Circumbinary Planets, Exoplanets, Apsidal Precession, Binary Stars, TESS, Exoplanet Detection, Orbital Dynamics, Planet Formation, Astrobiology, Vera C. Rubin Observatory, Spectroscopy, Eclipsing Binaries
