When Brian P. Powell and his team at NASA Goddard Space Flight Center analyzed light data from the Transiting Exoplanet Survey Satellite, they spotted something rare: a celestial triple act so perfectly choreographed that it's nearly impossible to witness from Earth. The system, designated TIC 295741342, is only one of a handful of known triply-eclipsing triple star systems ever discovered—and it's the most perfectly aligned of them all.
What makes this discovery remarkable is both the complexity of the system and how precisely it's arranged in space. At its heart lies a pair of sun-like stars orbiting each other every 4.75 days. These two stars, called TIC 295741342 Aa and TIC 295741342 Ab, are nearly identical main sequence stars with masses and sizes comparable to our sun and effective temperatures of 6,400 Kelvin. But here's where it gets extraordinary: this binary pair is itself orbited by a much larger tertiary companion every 1.13 years. That giant star, TIC 295741342 B, is 1.7 times the mass of our sun and expands to 10.6 times its diameter.
What makes this system stand out scientifically is its extraordinary geometry. The three stars orbit in nearly perfect alignment—with a mutual inclination of just 0.25 to 0.33 degrees. To understand what this means: imagine three dancers performing in perfect synchrony on the same plane. That's what's happening here, 3,080 light years away. This near-perfect coplanarity suggests the system formed through disk fragmentation billions of years ago, followed by orbital migration and gas dissipation—a tidy cosmic origin story that astronomers can now study in detail.
TESS detected this unusual configuration by observing what researchers call a "head-and-shoulders" eclipse. When the smaller binary pair passes directly behind the massive giant star, the light curve creates a distinctive three-part shape. The secondary of the eclipsing binary emerges first (the first shoulder), then both stars emerge together (the head), followed by the primary emerging alone (the second shoulder). This signature pattern reveals the relative sizes and brightness of all three stars with remarkable precision. The giant tertiary dominates the system's light in TESS's detection band at about 95 percent, while the primary and secondary of the binary contribute just 2.7 and 2.3 percent respectively.
The discovery underscores TESS's broader power as an observational tool. While the satellite primarily surveys about 200,000 bright stars near our sun searching for transiting exoplanets—alien worlds passing in front of their host stars—it's equally adept at revealing the secrets of stellar systems far closer to home. By tracking how mutual stellar eclipses twist and distort gravitational fields, TESS has opened new windows into how stars form and evolve in groups.
The researchers, led by Powell, estimate that this triple system is approximately 1.46 billion years old, with a metallicity of -0.337 dex. Their findings, published on the arXiv pre-print server in May, reveal that TIC 295741342 represents an exceptionally clean laboratory for understanding how multiple stars can maintain stable, synchronized orbits across vast distances. As the team concludes, this system boasts "by far the lowest mutual inclination among" known triply-eclipsing triple star systems—a distinction that makes it uniquely valuable for future study.