(ORDO NEWS) — Stars with the mass of the Sun or more are usually accompanied by one or more orbiting companion stars.
The system is formed when gravity compresses the gas and dust of an interstellar cloud into clumps dense enough to form stars.
According to one model, multiple star systems form when a cloud has little rotation. As a result, a disk is formed, which then fragments, forming several stars.
According to another model, cloud turbulence induces clumps to fragment into multiple systems. When the orbit of a pair of binary stars passes along our line of sight, the stars form an eclipsing binary system.
Ordinary such stars, about the size of the solar mass, have a typical period of a few days. Triplet star systems can also be eclipsing, but since the third star in a typical triplet has a more distant orbit (farther away to keep the system relatively stable and not eject one of the stars), its period is closer to a year, and for their discovery and study longer monitoring is required.
To date, over a million eclipsing binaries are known, but only twenty triple eclipsing systems have been published.
Astronomer Willie Torres was part of the team that used the Transiting Exoplanet Survey Satellite (TESS) to discover about fifty new triple eclipsing systems, twenty of which have reliable orbits for all three stars.
The team reports on six of these eclipsing triple systems, for which additional data have provided a more complete description of the stellar characters.
All six star systems are relatively old, about a billion years old. All of them are visible almost close to each other, and the inner binary star sometimes outshines the outer tertiary, and sometimes vice versa.
The masses of all twelve stars of the inner binary system are in the range from .7 to 1.8 solar masses. And six tertiary stars are larger, their masses vary from 1.5 to 2.3 solar masses.
In conclusion, the authors conclude that about 0.02% of close binary stars contain a third star in a flat configuration similar to their current set, meaning that there are probably several hundred thousand of them in our galaxy. They also note a possible connection between the triplets and even more complex star systems.
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