This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Astronomers have found a four-star system doing something that has never been confirmed before. The system, TIC 433545934, has two close pairs of stars orbiting each other.
While each pair eclipses its own two stars, as usual, only one pair eclipses the other. A paper outlining the properties of this unique system was submitted to the arXiv preprint server on Aug. 13. It has been accepted for publication in the journal Astronomy & Astrophysics.
When three or more stars are gravitationally bound together, they tend to organize into stable orbits to avoid flying apart or colliding. In triple-star systems, two stars orbit tightly around each other (the "inner binary"), while a third star orbits much farther out. More complicated quadruple-star systems have four stars.
These can be either "3+1" systems, with three stars in a nested triple plus one more star orbiting even farther out, or "2+2" systems, with two separate pairs of stars. Each pair orbits tightly around itself, while the two pairs orbit each other at a much greater distance. The focus of this study is 2+2 systems, in which both inner pairs happen to be "eclipsing binaries." This means each pair is oriented so that, when observed from Earth, the two stars in each pair periodically pass in front of each other, causing a regular dip in brightness.
When astronomers observe both pairs at once, their light blends into a single, more complex pattern. Detecting them, however, can be tricky because astronomers cannot immediately tell whether the pairs are truly gravitationally bound as one four-star system or simply two unrelated pairs that happen to line up by chance from Earth's perspective. They confirm the gravitational binding through eclipse timing variations—synchronized wobbles in both binaries' eclipse timing due to the presence of the other system.
In this study, astronomers led by Tamás Borkovits of the Baja Astronomical Observatory in Hungary studied a 2+2 type star system called TIC 433545934 that shows this matching timing pattern, confirming the two pairs really are gravitationally bound. What's more unique is that they also observed a rare event causing a "three-dipped" eclipse, where the two entire binary pairs are seen passing in front of each other. This makes TIC 433545934 the first-ever confirmed 2+2 quadruple star system that shows both: synchronized eclipse timing and eclipse between the whole pairs.
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